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Design and Implementation of a pair of Horn antenna for UIU microwave test setup

A thesis project submitted to the Department of Electrical and Electronic Engineering in Partial

Fulfillment of the Requirement for the Degree of

B.Sc. in Electrical and Electronic Engineering (EEE)

Department of Electrical and Electronic Engineering

United International University

Dhaka, Bangladesh

Fall 2010

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Design and Implementation of a pair of Horn antenna for UIU microwave test setup

By

Sadia Khandaker Monika Mousume Haque

ID: 021071060 ID: 021071062

Mubina Farhin Kazi Riaz Ullah

ID: 021071066 ID: 021071069

A thesis project submitted to the Department of Electrical and Electronic Engineering in Partial

Fulfillment of the Requirement for the Degree of

B.Sc. in Electrical and Electronic Engineering (EEE)

Supervisor

Mohammad Monir Morshed

Assistant Professor

Dept. of EEE

Fall 2010

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Dedication

To our Parents. . . . .

Thank you for your unconditional support with our studies. Thank you for giving us a

chance to prove and improve ourselves thorough all our walks of life. We love our

parents, thanks to both of you for helping to make us who we are, for teaching us to be

proud of who we are, for showing us how to be strong, for giving us the courage to be

weak, and giving us the strength to always strive for better and giving us the wisdom to

know when to turn away and when to change ahead. Our parents are our rock and

foundation.

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Declaration

It is hereby declared that this thesis is done by ourselves and has not been submitted

elsewhere for the award of any degree or diploma. There is lots of information that are

used from the published and unpublished work of others has been acknowledged in the

text. We have provided the list of references.

Signature of the Supervisor:

Mohammad Monir Morshed

Signature of the Candidates:

Sadia Khandaker Monika

Mousume Haque

Mubina Farhin

Kazi Riaz Ullah

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Acknowledgements

All praises are to the Supreme Being, Creator and Ruler of the universe, whose mercy keeps us

alive and enable to pursue our education in Electrical & Electronics Engineering to complete the

thesis on “Design and Implementation of a pair of Horn antenna for UIU microwave test

setup”.

We also send our salam to the Holy Prophet.

We thank our honorable supervisor Mr. Mohammad Monir Morshed, Assistant professor,

Department of Electronics and Electrical Engineering, United International University, for his

day to day supervision, constructive suggestions, valuable criticism and keen interest to carry

out this work. His scientific integrity and dedication have been inspiring us throughout our

graduate study and his patience and continuous encouragement helped our scientific approaches

during these years.

Cordial thanks to our parents, relatives and all our well wishers for their wholehearted

inspiration throughout the period of the thesis work.

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Abstract

This paper is our report for designing a pair of horn antenna for the UIU microwave test

setup. This work includes designing and implementation of a pair of pyramidal horn

antenna, and simulation of basic parameters using (HFSS). A brief theory on microwave

communication system, antenna basics, software introduction, design and

implementation of horn antenna will be discussed along the result of our design. Our

results and analysis show that the project was within the scope of our ability to design

and test the horn antennas.

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Table of Contents Acknowledgements ......................................................................................................... 5 List of figures.…………………………………………………………………………11

CHAPTER-1 INTRODUCTION TO MICROWAVE COMMUNICATION SYSTEM ........................................................................................................................ 15 1.1 Introduction ............................................................................................................... 15 1.2 History ...................................................................................................................... 16 1.3 Why use microwaves ................................................................................................ 17 1.4 Microwave sources ................................................................................................... 21 1.5 Microwave Transmitter and Receiver ....................................................................... 21 1.6 Microwave Link Networks ....................................................................................... 22 1.7 Forms of microwave communication ....................................................................... 25

1.7.1 Analog microwave communication .................................................................. 25 1.7.2 Digital microwave communication ................................................................... 25

1.8 Applications .............................................................................................................. 26

1.8.1 Long distance telephone calls ........................................................................... 26 1.8.2 Wireless LAN protocols.................................................................................... 26 1.8.3 Metropolitan area networks .............................................................................. 26 1.8.4 Wide Area Mobile Broadband Wireless Access ............................................... 26 1.8.5 Satellite communications systems .................................................................... 27 1.8.6 Radar ................................................................................................................. 27 1.8.7 Radio astronomy ............................................................................................... 27 1.8.8 Navigation ......................................................................................................... 27 1.8.9 Power ................................................................................................................ 28 1.8.10 Spectroscopy ................................................................................................... 28

1.9 Advantages ................................................................................................................ 29

1.9.1 Able to Transmit Large Quantities of Data ....................................................... 29 1.9.2 Relatively Low Costs ........................................................................................ 29

1.10 Limitations .............................................................................................................. 30

1.10.1 Line of Sight Technology ............................................................................... 30 1.10.2 Subject to Electromagnetic and Other Interference ........................................ 30

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Chapter-02 Antenna Basics .......................................................................................... 32 2.1 Antenna Basics: ........................................................................................................ 32

2.1.1 What is Antenna? : ............................................................................................ 32 2.1.2 Basic Types of Antenna: ................................................................................... 32

2.2 Basics Parameter of Antenna: ................................................................................... 33

2.2.2 Gain: .................................................................................................................. 34 2.2.3 Directivity: ........................................................................................................ 34 2.2.4 Beamwidth: ....................................................................................................... 35 2.2.5 VSWR: .............................................................................................................. 35 2.2.6 Radiation Intensity: ........................................................................................... 35 2.2.7 Beam Efficiency:............................................................................................... 35

2.3 Antenna Patterns: ...................................................................................................... 36

2.3.1 Antenna Pattern: ................................................................................................ 36 2.3.2 Antenna Field Types: ........................................................................................ 36 2.3.3 Antenna Field Regions: ..................................................................................... 36 2.3.4 Antenna Pattern Definitions: ............................................................................. 36 2.3.5 Principal Plane Patterns: ................................................................................... 37 2.3.6 Antenna Pattern Parameters .............................................................................. 37 2.4 Different types of antenna with their radiation patterns & characteristic: ........... 38

Chapter-03: Introduction of HFSS and Modeling of Dipole antenna ...................... 44 3.1-What is HFSS? ......................................................................................................... 44 3.2: Installing HFSS software ......................................................................................... 45

3.2.1-System Requirements ....................................................................................... 45 3.2.2- Installing the Ansoft HFSS Software .............................................................. 45 3.2.3- Starting Ansoft HFSS ...................................................................................... 45

3.3-Ansoft Terms ............................................................................................................ 45

3.3.1-Project Manager- .............................................................................................. 46 3.3.2-Property window ............................................................................................... 47 3.3.3-Ansoft 3D Modeler- .......................................................................................... 47 3.3.4-3D Modeler Design Tree .................................................................................. 48 3.3.6-Toolbars ............................................................................................................ 49 3.3.7-Ansoft HFSS Desktop....................................................................................... 49

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3.5-Set Solution Type ..................................................................................................... 50 3.6-Parametric Model Creation: ..................................................................................... 51

3.6.1-Overview of the 3D Modeler User Interface (Continued) ................................ 51

3.7-The Dipole Antenna simulation by HFSS V.9 ......................................................... 52

3.7.1-Getting started with HFSS 9.1: ......................................................................... 52 3.7.2-Opening a New Project ..................................................................................... 53 3.7.3-Creating the 3D Model ..................................................................................... 54

3.8-Create Dipole ............................................................................................................ 54

3.8.1-Create waveguide .............................................................................................. 54 3.8.2- Drawing the Dipole .......................................................................................... 56

3.9- Creating the port ...................................................................................................... 59 3.10- Radiation Boundary ............................................................................................... 63 3.11- Solution Setup ....................................................................................................... 65 3.12- Structure Analysis ................................................................................................. 66 3.13- Create Reports ....................................................................................................... 67 Chapter 4: Parametric Study: Horn Antenna ........................................................... 73 4.1: Types of Horn Antennas .......................................................................................... 73 4.2: Horn antenna parameters ......................................................................................... 74 4.3: Modeling of Horn antenna in HFSS ........................................................................ 74

4.3.1: Getting started with HFSS 9.1: ........................................................................ 74 4.3.2: Opening a New Project .................................................................................... 75 4.3.3: Creating the 3D Model ..................................................................................... 76 4.3.4: Create Horn Top .............................................................................................. 77 4.3.5: Create funnel base: ........................................................................................... 78 4.3.6: Create the funnel: ............................................................................................. 79 4.3.7: Complete the Horn ........................................................................................... 79 4.3.8: Create Air Box around the Horn Antenna ....................................................... 80 4.3.9: Assigning Boundaries and excitations ............................................................. 81 4.3.10: Create Radiation Boundary ............................................................................ 82 4.3.11: Analysis Setup ............................................................................................... 83 4.3.12: Model Validation ........................................................................................... 84 4.3.13: Analyze .......................................................................................................... 84

4.4: Creating Report ........................................................................................................ 85

4.4.1: Create 3D Polar Far Field Plot ......................................................................... 85 4.4.2: Creating rectangular plot .................................................................................. 86

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4.5: Compute Antenna Parameter ................................................................................... 89 4.6 Create animation of Electric field and Magnetic field .............................................. 90 4.7 Simulation results of different types of Horn antenna .............................................. 91

4.7.1 Simulation Results for H-plane sectoral Horn antenna ..................................... 91 4.7.2 3D Polar plot for H-plane sectoral Horn: .......................................................... 91 4.7.3 Antenna parameters of H-sectoral Horn: .......................................................... 92 4.7.4 Simulation Results for H-plane sectoral Horn antenna ..................................... 93 4.7.5 3D Polar plot for E-plane sectoral Horn: .......................................................... 93 4.7.6 Antenna parameters of H-sectoral Horn: .......................................................... 94 4.7.7 Simulation Results for Pyramidal Horn antenna ............................................... 95 4.7.8 3D Polar plot for E-plane sectoral Horn: .......................................................... 95 4.7.9 Antenna parameters of Pyramidal Horn: .......................................................... 96 4.7.10 Antenna as impedance matching device ......................................................... 97 4.7.11 Rectangular plot and radiation pattern of Directivity and Gain ...................... 98

Chapter 5: Implementation of Horn Antenna ......................................................... 100 5.1 Equipments / Instruments ....................................................................................... 100 5.2 Diagram of instruments setup ................................................................................. 100 5.3 Procedure ................................................................................................................ 101 5.4 Tabular Column ...................................................................................................... 101 5.5 Graphical Representation of the results .................................................................. 102 5.6 Snap shots of microwave test bench and Horn antenna .......................................... 102

5.6.1 Microwave test bench ..................................................................................... 102 5.6.2 Horn antenna ................................................................................................... 103

Chapter 6 Conclusion ................................................................................................. 105

References……………………………………………………………………………106

List of Tables

Table 1.1: IEEE Frequency Spectrum ............................................................................ 19

Table 5.1 Experimental Results .................................................................................... 101

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List of Figures

Fig 1.1: Microwave Communication System ............................................................ 16 Fig 1.2: Microwave transmitter and receiver ............................................................. 22 Fig 2.1: Receiving Antenna ....................................................................................... 32 Fig 2.2: Transmitting Antenna ................................................................................... 32 Fig 2.3: Propagation of TEM wave using transmitting & receiving antenna ............ 33 Fig 2.4: Antenna Pattern Parameters (Normalized Power Pattern) ........................... 37 Fig 2.5: Monopole Antenna ....................................................................................... 38 Fig 2.6(a)&(b): Elevation ........................................................................................... 38 Fig 2.7: λ/2 Dipole Antenna ....................................................................................... 39 Fig 2.8(a)&(b): Elevation ........................................................................................... 39 Fig 2.9: Biconical Antenna ........................................................................................ 40 Fig 2.10(a): Elevation ................................................................................................ 40 Fig 2.10(b): Azimuth.................................................................................................. 40 Fig 2.11: Yagi Antenna .............................................................................................. 41 Fig 2.12(a)&(b): Elevation ......................................................................................... 41 Fig 2.13 Horn antenna ................................................................................................ 42 Fig 2.14(a): Elevation (3 dB beamwidth = 56λ/dz) ................................................... 42 Fig 2.14(b): Azimuth (3 dBbeamwidth = 70 8E/dx) .................................................. 42 Fig:3.1Differents terms of ansoft ............................................................................... 46 Fig:3.2 Differents terms of Project window............................................................... 46 Fig:3.2(a) Differents terms of Property window ........................................................ 47 Fig:3.2(b)Different terms of 3D modeler window .................................................... 47 Fig:3.2(c)Different terms of 3D model ...................................................................... 48 Fig:3.3 Modeler design tree ....................................................................................... 48 Fig:3.4 Toolbars of ansoft HFSS ............................................................................... 49 Fig:3.5 Ansoft desktop design tree. ........................................................................... 50 Fig:3.6 Status bar ....................................................................................................... 51 Fig:3.7Active Cursor .................................................................................................. 51 Fig:3.8 Project menu window .................................................................................... 53 Fig: 3.9 Solution type window ................................................................................... 53 Fig. 3.10 Model Unit window .................................................................................... 54 Fig. 3.11 set the default material ................................................................................ 54 Fig. 3.12 Property window ........................................................................................ 55 Fig. 3.13 Final variable table .................................................................................... 55 Fig. 3.14 Drawing dipole ........................................................................................... 56 Fig. 3.15 appeared table by creating the dipole ......................................................... 57 Fig. 3.16 table from model menu .............................................................................. 57 Fig. 3.17 form the duplicate dipole in the 180 degree position ................................ 58 Fig. 3.18 Duplicate Around Axis window ................................................................ 58 Fig. 3.19 Final dipole structure ................................................................................. 59 Fig:3.20 (a)&(b) Selecting YZ plane ......................................................................... 59

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Fig. 3.21 Property window ........................................................................................ 60 Fig. 3.22 View of a 3D modeler window .................................................................. 60 Fig. 3.23 Property window ........................................................................................ 61 Fig. 3.24 Port assumption ......................................................................................... 61 Fig. 3.25 Port assigning window ................................................................................ 62 Fig. 3.26 HFSS window after assigning port ............................................................. 62 Fig. 3.27 Property window ......................................................................................... 63 Fig. 3.28 Property window ......................................................................................... 63 Fig:3.29 Select Face Window ................................................................................... 64 Fig:3.30 Select Radiation port .................................................................................. 64 Fig:3.31 Select Setup window ................................................................................... 65 Fig:3.32 Select Setup window .................................................................................. 66 Fig:3.33 Validation Check Window .......................................................................... 66 Fig. 3.34 Analyzing window ...................................................................................... 67 Fig. 3.35 Select the result patterns ............................................................................. 67 Fig:3.36 Trace Window ............................................................................................. 68 Fig. 3.37 Rectangular plot ......................................................................................... 68 Fig. 3.38 (a) Define the air box as infinite sphere; (b) Compute antenna properties . 69 Fig: 3.39 Results of antenna parameters .................................................................... 69 Fig: 3.40 Display type ................................................................................................ 70 Fig. 3.41 Traces Window ........................................................................................... 70 Fig. 3.42 Traces Window ........................................................................................... 71 Fig. 3.43 Radiation pattern of Directivity .................................................................. 71 Fig: 4.1 H-plane sectoral horn .................................................................................... 73 Fig: 4.2 E-plane sectoral horn .................................................................................... 73 Fig: 4.3 Pyramidal horn ............................................................................................. 73 Fig: 4.4 Conical horn ................................................................................................. 73 Fig: 4.5 Project menu window ................................................................................... 75 Fig: 4.6 Solution type window ................................................................................... 75 Fig. 4.7 Model Unit window ...................................................................................... 76 Fig. 4.8 Waveguide .................................................................................................... 76 Fig. 4.9 Waveguide and Funnel Base ........................................................................ 78 Fig. 4.10 Project menu ............................................................................................... 79 Fig. 4.11 Highlight the Horn top and funnel base ...................................................... 79 Fig. 4.12 A complete horn after connection ............................................................... 80 Fig. 4.13 A complete horn after unite ........................................................................ 80 Fig. 4.14 An Air box outside the horn ....................................................................... 81 Fig. 4.15 Select Face window .................................................................................... 81 Fig. 4.16 Wave Port ................................................................................................... 82 Fig. 4.17 Solution setup window ............................................................................... 83 Fig: 4.18 Sweep setup window .................................................................................. 83 Fig. 4.19 Validation Check Window ......................................................................... 84 Fig. 4.20 Analyzing window ...................................................................................... 84 Fig. 4.21 3D Polar plot ............................................................................................... 85

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Fig. 4.22 Trace window ............................................................................................. 86 Fig. 4.23 Rectangular plot .......................................................................................... 87 Fig. 4.24 Traces Window ........................................................................................... 88 Fig. 4.25 Rectangular plot for real and imaginary impedance of horn antenna ......... 88 Fig. 4.26 (a) Define the air box as infinite sphere; (b) Compute antenna properties . 89 (c) Results of antenna parameters .............................................................................. 89 Fig. 4.27(a) Electric field propagation animation (b) Magnetic field propagation animation .................................................................................................................... 90 Fig. 4.28 H-plane sectoral horn .................................................................................. 91 Fig. 4.29 3D polar plot ............................................................................................... 91 Fig. 4.30 Antenna parameters of H-sectoral Horn ..................................................... 92 Fig. 4.31 E-plane sectoral horn .................................................................................. 93 Fig. 4.32 3D polar plot ............................................................................................... 93 Fig. 4.33 Antenna parameters of E-sectoral Horn ..................................................... 94 Fig: 4.34 Pyramidal horn ........................................................................................... 95 Fig. 4.35 3D polar plot ............................................................................................... 95 Fig. 4.36 Antenna parameters of Pyramidal Horn ..................................................... 96 Fig. 4.37 Impedance parameter of waveguide ........................................................... 97 Fig. 4.38Impedance parameter of pyramidal horn ..................................................... 97 Fig. 4.39 Rectangular plot of Directivity ................................................................... 98 Fig. 4.40 Radiation pattern of Directivity .................................................................. 98 Fig. 5.1 Measurement of Horn ................................................................................. 100 Fig. 5.2 Microwave bench set-up to measure the gain of horn antenna .................. 100 Fig. 5.3 Gain Vs Distance Graph ............................................................................. 102 Fig. 5.4 Microwave test bench of UIU lab ............................................................... 102 Fig. 5.5 Pyramidal Horn antenna ............................................................................. 103 Fig. 5.6 Microwave test bench when horn antenna is connected ............................. 103

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Chapter 1

Introduction to Microwave

Communication System

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CHAPTER-1

INTRODUCTION TO MICROWAVE COMMUNICATION SYSTEM 1.1 Introduction Microwave communication is the transmission of signals via radio using a series of microwave towers. Microwave communication is known as a form of “line of sight” communication, because there must be nothing obstructing the transmission of data between these towers for signals to be properly sent and received. The term microwave is associated to electromagnetic waves of frequency of the order of MHz .Since the energy carried by the wave is directly proportional to their frequency they are of great use in distance communication. For a simple microwave communication system, a radiator, a reflector and one receiver antenna are essential. As the wave penetrates through the atmosphere a satellite reflector is usually used. The objective of microwave communication systems is to transmit information from one place to another without interruption, and clear reproduction at the receiver. Fig. 1.1 indicates how this is achieved in its simplest form. Above 100 MHz the waves travel in straight lines and can therefore be narrowly focused. Concentrating all the energy into a small beam using a parabolic antenna (like the satellite TV dish) gives a much higher signal to noise ratio, but the transmitting and receiving antennas must be accurately aligned with each other. Before the advent of fiber optics, these microwaves formed the heart of the long distance telephone transmission system. In its simplest form the microwave link can be one hop, consisting of one pair of antennas spaced as little as one or two kilometers apart, or can be a backbone, including multiple hops, spanning several thousand kilometers. A single hop is typically 30 to 60 km in relatively flat regions for frequencies in the 2 to 8 GHz bands. When antennas are placed between mountain peaks, a very long hop length can be achieved. Hop distances in excess of 200 km are in existence. The "line-of-sight" nature of microwaves has some very attractive advantages over cable systems. Line of sight is a term which is only partially correct when describing microwave paths. Atmospheric conditions and certain effects modify the propagation of microwaves so that even if the designer can see from point A to point B (true line of

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sight), it may not be possible to place antennas at those two points and achieve a satisfactory communication performance. In order to overcome the problems of line-of-sight and power amplification of weak signals, microwave systems use repeaters at intervals of about 25 to 30 km in between the transmitting receiving stations. The first repeater is placed in line-of-sight of the transmitting station and the last repeater is placed in line-of-sight of the receiving station. Two consecutive repeaters are also placed in line-of-sight of each other. The data signals are received, amplified, and re-transmitted by each of these stations.

Figure 1.1: Microwave Communication System

1.2 History It is necessary in a study of the history of microwave communications to start with the monumental discoveries and demonstrations in the fields of electrical communication and the application of the principles of electromagnetic wave propagation to radio. The history of microwave communications includes major discoveries of Morse, Maxwell, Hertz, Marconi, and other pioneers of the radio and electronics fields. This paper traces the early work which led to wireless communications and the long struggle to achieve practical microwave radio. Even though the first microwave line-of-sight systems were demonstrated and placed in service during the 1930's, it was not until the late 1940's and early 1950's that huge transcontinental microwave transmission systems were implemented. The 1960's and 1970's witnessed significant progress in the technology and application of line-of-sight microwave communication systems. Other microwave systems including troposcatter, satellite, and millimeter waveguide transmission systems were also developed during the 1960's and 1970's. The past 100

Transmitter Receiver Input Output

Transmission

line

Transmission

line

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years have witnessed very significant breakthroughs in radio technology, particularly at microwave frequencies, that have had an enormous impact on the world's societies through improved communications for the populace, business, and governments. Enormous strides in the development of microwave technology were made during World War II, with the bulk of the effort aimed at radar systems. South worth’s waveguide group at Bell Labs become heavily involved in this effort and invented many waveguide components for radar, including waveguide lobe switches, rotary joints, improved filters, waveguide modulators and demodulators, phasing devices, waveguide hybrids including the magic-tee, directional couplers, attenuators, power measuring devices and other instruments. While these components were extremely useful for the radar work, they were also applicable for communication systems. The technology used for microwave communication was developed in the early 1940’s by Western Union. The first microwave message was sent in 1945 from towers located in New York and Philadelphia. Following this successful attempt, microwave communication became the most commonly used data transmission method for telecommunications service providers.

1.3 Why use microwaves Communication using electromagnetic radiation (except for light) began early in this century, and most early practical systems used very long wavelengths (low frequencies) which traveled great distances. Eventually, electronics were developed, including the vacuum tube (or "valve") which allowed controlled frequencies and modulation. This led to the use of higher frequencies, many channels, and commercial and industrial radio. During the 1930's and 1940's various experimenters discovered that higher frequencies could bring other advantages to communications. Some of these experimenters were government agencies and the military - some were universities, and some were private individuals. Among these discoveries were that microwaves are easier to control (than longer wavelengths) because small antennas could direct the waves very well. One advantage of such control is that the energy could be easily confined to a tight beam (expressed as narrow beam width). This beam could be focused on another antenna dozens of miles away, making it very difficult for someone to intercept the conversation. Another characteristic is that because of their high frequency, greater amounts of information could be put on them (expressed as increased modulation bandwidth). Both of these advantages (narrow beam width and modulation bandwidth) make microwaves very useful for RADAR as well as communications. Eventually, these qualities led to the use of microwaves by the telephone companies. They placed towers every 30 to 60 miles each with antennas, receivers and transmitters. These would relay hundreds or even thousands of voice conversations across the country. The ability to modulate with a wide bandwidth permitted so many

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conversations on just one signal, and the reduction in beam width made this reasonably secure. In the 1950s experiments were conducted that showed the potential to connect the two coasts of the US via these microwave circuits to produce television programming on a continental basis, and true television networks were born. Amateur radio interests in microwaves have mostly been for the challenge of working with such esoteric frequencies that require specialized techniques in design, fabrication and testing. Furthermore, in order to reach beyond LOS (line-of-sight) amateurs have spent countless hours carefully measuring propagation phenomena. Amateurs have carried on conversations using 10GHz well over 1,000 miles, and have bounced signals at that frequency off the moon. For more information about amateur radio uses of microwaves set your browser to www.wa1mba.org, contact a local VHF/Microwave Amateur radio club, or contact the ARRL. A photon is a quantum of electromagnetic energy. Physicists think of electromagnetic energy as having a "dual nature", in that some experiments reveal its nature as a particle which we call a photon and other experiments reveal its nature as a wave. When it comes to lower frequencies (longer wavelengths), such as microwaves, VHF, and the like, it becomes much less convenient to think of energy in the form of photons, but there is no specific reason to decide that only one nature exists at these longer wavelengths. Sometimes photons are referred to when describing an RF interaction with matter. The author does not know of any other word to describe the particulate nature of a propagating RF energy field except "photon". When the interaction with matter converts the energy into a mechanical form, we sometimes refer to the energy packets as "phonons". This is not a propagating Electro-Magnetic (EM) field, but rather a sound wave, and at the most minute level, even mechanical energy is quantized. In most antenna, transmission line, waveguide, and quasi-optic formulations, the EM field is described according to its wave-like nature. When dealing with the interaction between a microwave field and a molecule of Oxygen (for instance), in order to understand just why there are specific resonant frequencies of the molecule, a quantized nature re-appears, and the notion of the field expressed as photons can make sense. The interactions between matter and EM fields have clearly different properties when comparing the interaction that causes a change in mechanical vibration with the interaction that causes a change in electron orbital state. The first occurs in the microwave and millimeter wave range - such as the serious absorption of 22 GHz signals by water vapor in the atmosphere. Here the interaction causes vibration and heat. To cause changes in electron orbital states, infrared, visible and UV range wavelengths are involved - such as is evidenced by florescence and lasers. In these cases much more than conversion to heat occurs. We call the second group of wavelengths "light" and the word "photon" is derived from Greek for light.

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Here are some frequency bands, exact frequencies, approximate wavelength and their applications.

Table 1.1: IEEE Frequency Spectrum SL. No Frequency Band Frequency Wavelength Application

1 ELF (Extreme Low Frequency) 30-300 Hz 10,000-1,000

km Radio band & radio communication

2 VF (Voice Frequency) 300-3,000 Hz 1,000-100

km Transmits voice signal

3 VLF (Very Low Frequency) 3-30 kHz 100-10 km

Communicate with submarines near the surface, radio navigation beacons (alpha) and time signals (beta), electromagnetic geophysical surveys

4 LF (Low Frequency) 30-300 kHz 10-1 km

AM broadcasting as the long wave band, aircraft beacon, navigation (LORAN), information, and weather systems

5 MF (Medium Frequency)

300-3,000 kHz 1-0.1 km

Non-directional navigational radio beacons (NDBs) for maritime and aircraft navigation

6 HF (High Frequency) 3-30 MHz 100-10 m

Amateur radio operators, who can take advantage of direct, long-distance (often inter-continental) communications and the "thrill factor" resulting from making contacts in variable conditions

7 VHF (Very High Frequency) 30-300 MHz 10-1 m

Identify faults and defects in ceramic insulators

8 UHF (Ultra High Frequency )

300-3,000 MHz 100-10 cm

Transmission of television signals

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9 SHF (Super High Frequency) 3-30 GHz 10-1 cm

Microwave devices, WLAN, most modern radars

10 EHF (Extreme High Frequency) 30-300 GHz 1-0.1 cm

Radio astronomy and remote sensing

11 Decimillimeter 300-3,000 GHz 1-0.1 mm

Transmits signal

12 P Band 0.23-1 GHz 130-30 cm Radar

13 L Band 1-2 GHz 30-15 cm Satellite

14 S Band 2-4 GHz 15-7.5 cm

Weather radar, surface ship radar, and some communications satellites, especially those used by NASA to communicate with the Space Shuttle and the International Space Station

15 C Band 4-8 GHz 7.5-3.75 cm Long-distance radio telecommunications

16 X Band 8-12.5 GHz 3.75-2.4 cm

Radar receivers, electronic counter measures, decoys, jammers, and phased array systems

17 Ku Band 12.5-18 GHz 2.4-1.67 cm Satellite communications

18 K Band 18-26.5 GHz 1.67-1.13 cm Conforming bandage to hold dressings in place

19 Ka Band 26.5-40 GHz 1.13-0.75 cm Satellite communication

20 Millimeter wave 40-300 GHz 7.5-1 mm

Transmitting large amounts of computer data, cellular communications, and radar

21 Sub millimeter wave 300-3,000 GHz 1-0.1 mm

Pulsed magnetic field

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1.4 Microwave sources Vacuum tube devices operate on the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields, and include the magnetron, klystron, traveling-wave tube (TWT), and gyrotron. These devices work in the density modulated mode, rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream. Cut away view inside a cavity magnetron as used in a microwave oven. Low power microwave sources use solid-state devices such as the field-effect transistor (at least at lower frequencies), tunnel diodes, Gunn diodes, and IMPATT diodes. A maser is a device similar to a laser, which amplifies light energy by stimulating the emitted radiation. The maser, rather than amplifying light energy, amplifies the lower frequency, longer wavelength microwaves. The sun also emits microwave radiation, and most of it is blocked by Earth's atmosphere. The Cosmic Microwave Background Radiation (CMBR) is a source of microwaves that supports the science of cosmology's Big Bang theory of the origin of the Universe.

1.5 Microwave Transmitter and Receiver Fig.1.2 below shows block diagram of microwave link transmitter and receiver section The voice, video, or data channels are combined by a technique known as multiplexing to produce a BB signal. This signal is frequency modulated to an IF and then up converted (heterodyned) to the RF for transmission through the atmosphere. The reverse process occurs at the receiver. The microwave transmission frequencies are within the approximate range 2 to 24 GHz.

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Figure 1.2: Microwave transmitter and receiver

The frequency bands used for digital microwave radio are recommended by the CCIR. Each recommendation clearly defines the frequency range, the number of channels that can be used within that range, the channel spacing the bit rate and the polarization possibilities.

1.6 Microwave Link Networks A microwave link is a communications system that uses a beam of radio waves in the microwave frequency range to transmit information between two fixed locations on the earth. They are crucial to many forms of communication and impact a broad range of industries. Broadcasters use microwave links to send programs from the studio to the transmitter location, which might be miles away. Microwave links carry cellular telephone calls between cell sites. Wireless Internet service providers use microwave links to provide their clients with high-speed Internet access without the need for cable connections. Telephone companies transmit calls between switching centers over microwave links, although fairly recently they have been largely supplanted by fiber-optic cables. Companies and government agencies use them to provide communications networks between nearby facilities within an organization, such as a company with several buildings within a city.

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One of the reasons microwave links are so adaptable is that they are broadband. That means they can move large amounts of information at high speeds. Another important quality of microwave links is that they require no equipment or facilities between the two terminal points, so installing a microwave link is often faster and less costly than a cable connection. Finally, they can be used almost anywhere, as long as the distance to be spanned is within the operating range of the equipment and there is clear path (that is, no solid obstacles) between the locations. Microwaves are also able to penetrate rain, fog, and snow, which mean bad weather doesn’t disrupt transmission. A simplified rendering of a microwave link. A microwave link is a communications system that uses a beam of radio waves in the microwave frequency range to transmit information between two fixed locations on the earth. A simple one-way microwave link includes four major elements: a transmitter, a receiver, transmission lines, and antennas. These basic components exist in every radio communications system, including cellular telephones, two-way radios, wireless networks, and commercial broadcasting. But the technology used in microwave links differs markedly from that used at the lower frequencies (longer wavelengths) in the radio spectrum. Techniques and components that work well at low frequencies are not useable at the higher frequencies (shorter wavelengths) used in microwave links. For example, ordinary wires and cables function poorly as conductors of microwave signals. On the other hand, microwave frequencies allow engineers to take advantage of certain principles that are impractical to apply at lower frequencies. One example is the use of a parabolic or “dish” antenna to focus a microwave radio beam. Such antennas can be designed to operate at much lower frequencies, but they would be too large to be economical for most purposes. In a microwave link the transmitter produces a microwave signal that carries the information to be communicated. That information—the input—can be anything capable of being sent by electronic means, such as a telephone call, television or radio programs, text, moving or still images, web pages, or a combination of those media. The transmitter has two fundamental jobs: generating microwave energy at the required frequency and power level, and modulating it with the input signal so that it conveys meaningful information. Modulation is accomplished by varying some characteristic of the energy in response to the transmitter’s input. Flashing a light to transmit a message in Morse Code is an example of modulation. The differing lengths of the flashes (the dots and dashes), and the intervals of darkness between them, convey the information—in this case a text message. The second integral part of a microwave link is a transmission line. This line carries the signal from the transmitter to the antenna and, at the receiving end of the link, from the antenna to the receiver. In electrical engineering, a transmission line is anything that conducts current from one point to another. Lamp cord, power lines, telephone wires and speaker cable are common transmission lines. But at microwave frequencies, those

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media excessively weaken the signal. In their place, engineers use coaxial cables and, especially, hollow pipes called waveguides. The third part of the microwave system is the antennas. On the transmitting end, the antenna emits the microwave signal from the transmission line into free space. “Free space” is the electrical engineer’s term for the emptiness or void between the transmitting and receiving antennas. It is not the same thing as “the atmosphere,” because air is not necessary for any type of radio transmission (which is why radio works in the vacuum of outer space). At the receiver site, an antenna pointed toward the transmitting station collects the signal energy and feeds it into the transmission line for processing by the receiver. Antennas used in microwave links are highly directional, which means they tightly focus the transmitted energy, and receive energy mainly from one specific direction. This contrasts with antennas used in many other communications systems, such as broadcasting. By directing the transmitter’s energy where it's needed—toward the receiver—and by concentrating the received signal, this characteristic of microwave antennas allows communication over long distances using small amounts of power. Between the link’s antennas lies another vital element of the microwave link—the path taken by the signal through the earth’s atmosphere. A clear path is critical to the microwave link’s success. Since microwaves travel in essentially straight lines, man-made obstacles (including possible future construction) that might block the signal must either be overcome by tall antenna structures or avoided altogether. Natural obstacles also exist. Flat terrain can create undesirable reflections, precipitation can absorb or scatter some of the microwave energy, and the emergence of foliage in the spring can weaken a marginally strong signal, which had been adequate when the trees were bare in the winter. Engineers must take all the existing and potential problems into account when designing a microwave link. At the end of the link is the final component, the receiver. Here, information from the microwave signal is extracted and made available in its original form. To accomplish this, the receiver must demodulate the signal to separate the information from the microwave energy that carries it. The receiver must be capable of detecting very small amounts of microwave energy, because the signal loses much of its strength on its journey. This entire process takes place at close to the speed of light, so transmission is virtually instantaneous even across long distances. With all of their advantages, microwave links are certain to be important building blocks of the world’s communications infrastructure for years to come.

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1.7 Forms of microwave communication Microwave communication takes place both analog and digital formats. While digital is the most advanced form of microwave communication, both analog and digital methods pose certain benefits for users.

1.7.1 Analog microwave communication

Analog microwave communication systems originated in the 1950s and their development over subsequent decades has witnessed evolution from analog to digital and from PDH to SDH. Higher modulation efficiency, greater bandwidth, longer transmission distances, and enhanced reliability denote continual progress that remains essentially market driven. Analog microwave communication systems, operated at a frequency of two gigahertz (2 GHz), have been used by railroad companies, power companies, pipeline operators and state and local governments to support private networks for voice and data communication.

1.7.2 Digital microwave communication

Digital microwave communication refers to a type of communication mode which uses microwave (frequency) to carry digital information through the electric wave space, transmit independent information and conduct regeneration. Microwave is weak in diffraction and it is only line-of-sight communication, therefore, it has a limited transmission distance. In long-distance transmission, relay is needed to connect sites. Thus, it is called microwave relay communication. Digital microwave communication utilizes more advanced, more reliable technology. It is much easier to find equipment to support this transmission method because it is the newer form of microwave communication. Because it has a higher bandwidth, it also allows transmitting more data using more verbose protocols. The increased speeds will also decrease the time it takes to poll microwave site equipment. This is more reliable format provides for more reliable reporting with advanced communication equipment, while also allowing to bring in LAN connection when it becomes available at the site.

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1.8 Applications Microwave communication systems handle a large fraction of the world’s international and other long haul telephone, data and television transmissions. Most of the currently developing wireless telecommunications systems, such as direct broadcast satellite (DBS) television, personal communication systems (PCSs), wireless local area networks (WLANS), cellular video (CV) systems and global positioning satellite (GPS) systems rely heavily on microwave technology.

1.8.1 Long distance telephone calls

Before the advent of fiber-optic transmission, most long distance telephone calls were carried via networks of microwave radio relay links run by carriers such as AT&T Long Lines. Starting in the early 1950s, frequency division multiplex was used to send up to 5,400 telephone channels on each microwave radio channel, with as many as ten radio channels combined into one antenna for the hop to the next site, up to 70 km away.

1.8.2 Wireless LAN protocols

Wireless LAN protocols, such as Bluetooth and the IEEE 802.11 specifications, also use microwaves in the 2.4 GHz ISM band, although 802.11a uses ISM band and U-NII frequencies in the 5 GHz range. Licensed long-range (up to about 25 km) Wireless Internet Access services have been used for almost a decade in many countries in the 3.5–4.0 GHz range. The FCC recently carved out spectrum for carriers that wish to offer services in this range in the U.S. — with emphasis on 3.65 GHz. Dozens of service providers across the country are securing or have already received licenses from the FCC to operate in this band. The WIMAX service offerings that can be carried on the 3.65 GHz band will give business customers another option for connectivity.

1.8.3 Metropolitan area networks

MAN protocols, such as WiMAX (Worldwide Interoperability for Microwave Access) based in the IEEE 802.16 specification. The IEEE 802.16 specification was designed to operate between 2 to 11 GHz. The commercial implementations are in the 2.3 GHz, 2.5 GHz, 3.5 GHz and 5.8 GHz ranges.

1.8.4 Wide Area Mobile Broadband Wireless Access

MBWA protocols based on standards specifications such as IEEE 802.20 or ATIS/ANSI HC-SDMA (e.g. iBurst) are designed to operate between 1.6 and 2.3 GHz to give mobility and in-building penetration characteristics similar to mobile phones but with vastly greater spectral efficiency.

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Some mobile phone networks, like GSM, use the low-microwave/high-UHF frequencies around 1.8 and 1.9 GHz in the America and elsewhere, respectively. DVB-SH and S-DMB use 1.452 to 1.492 GHz, while proprietary/incompatible satellite radio in the U.S. uses around 2.3 GHz for DARS. Microwave radio is used in broadcasting and telecommunication transmissions because, due to their short wavelength, highly directional antennas are smaller and therefore more practical than they would be at longer wavelengths (lower frequencies). There is also more bandwidth in the microwave spectrum than in the rest of the radio spectrum; the usable bandwidth below 300 MHz is less than 300 MHz while many GHz can be used above 300 MHz. Typically, microwaves are used in television news to transmit a signal from a remote location to a television station from a specially equipped van. See broadcast auxiliary service (BAS), remote pickup unit (RPU), and studio/transmitter link (STL).

1.8.5 Satellite communications systems

Most satellite communications systems operate in the C, X, Ka, or Ku bands of the microwave spectrum. These frequencies allow large bandwidth while avoiding the crowded UHF frequencies and staying below the atmospheric absorption of EHF frequencies. Satellite TV either operates in the C band for the traditional large dish fixed satellite service or Ku band for direct-broadcast satellite. Military communications run primarily over X or Ku-band links, with Ka band being used for Milstar.

1.8.6 Radar

Radar uses microwave radiation to detect the range, speed, and other characteristics of remote objects. Development of radar was accelerated during World War II due to its great military utility. Now radar is widely used for applications such as air traffic control, weather forecasting, navigation of ships, and speed limit enforcement.

1.8.7 Radio astronomy

Most radio astronomy uses microwaves. Usually the naturally-occurring microwave radiation is observed, but active radar experiments have also been done with objects in the solar system, such as determining the distance to the Moon or mapping the invisible surface of Venus through cloud cover.

1.8.8 Navigation

Global Navigation Satellite Systems (GNSS) including the Chinese Beidou, the American Global Positioning System (GPS) and the Russian GLONASS broadcast navigational signals in various bands between about 1.2 GHz and 1.6 GHz.

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1.8.9 Power

A microwave oven passes (non-ionizing) microwave radiation (at a frequency near 2.45 GHz) through food, causing dielectric heating by absorption of energy in the water, fats and sugar contained in the food. Microwave ovens became common kitchen appliances in Western countries in the late 1970s, following development of inexpensive cavity magnetrons. Water in the liquid state possesses many molecular interactions which broaden the absorption peak. In the vapor phase, isolated water molecules absorb at around 22 GHz, almost ten times the frequency of the microwave oven. Microwave heating is used in industrial processes for drying and curing products. Many semiconductor processing techniques use microwaves to generate plasma for such purposes as reactive ion etching and plasma-enhanced chemical vapor deposition (PECVD). Microwave frequencies typically ranging from 110 – 140 GHz are used in stellarators and more notably in tokamak experimental fusion reactors to help heat the fuel into a plasma state. The upcoming ITER Thermonuclear Reactor is expected to range from 110–170 GHz and will employ Electron Cyclotron Resonance Heating (ECRH). Microwaves can be used to transmit power over long distances, and post-World War II research was done to examine possibilities. NASA worked in the 1970s and early 1980s to research the possibilities of using solar power satellite (SPS) systems with large solar arrays that would beam power down to the Earth's surface via microwaves. Less-than-lethal weaponry exists that uses millimeter waves to heat a thin layer of human skin to an intolerable temperature so as to make the targeted person move away. A two-second burst of the 95 GHz focused beam heats the skin to a temperature of 130 °F (54 °C) at a depth of 1/64th of an inch (0.4 mm). The United States Air Force and Marines are currently using this type of Active Denial System.

1.8.10 Spectroscopy

Microwave radiation is used in electron paramagnetic resonance (EPR or ESR) spectroscopy, typically in the X-band region (~9 GHz) in conjunction typically with magnetic fields of 0.3 T. This technique provides information on unpaired electrons in chemical systems, such as free radicals or transition metal ions such as Cu(II). The microwave radiation can also be combined with electrochemistry, microwave enhanced electrochemistry.

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1.9 Advantages The various advantages of microwave communications are as follows:

• Large bandwidth availability • Less power requirement with the use of repeaters • Easily penetrable to the areas like even the ionosphere • Line of sight propagation • Reduces the size of the antenna • Can accommodate more number of channels • No cabling needed between sites • Multichannel transmission • Provides a high data rate • Cost of purchasing towers for transmission is pretty low

1.9.1 Able to Transmit Large Quantities of Data

According to "Microwave Communication," microwave radio systems have the capacity to broadcast great quantities of information because of their higher frequencies. They use repeaters (a device that receives the transmitting signal through one antenna, converts it into an electrical signal and retransmits it) to transmit large volumes of data over great distances. Microwave radio communication systems propagate signals through the earth's atmosphere. These signals are sent between transmitters and receivers that lie on top of towers. This allows microwave radio systems to transmit thousands of data channels between two points without relying on a physical transmitting medium (optical fibers or metallic cables).

1.9.2 Relatively Low Costs

Microwave communication systems have relatively low construction costs compared with other forms of data transmission, such as wire-line technologies. A microwave communication system does not require physical cables or expensive attenuation equipment (devices that maintain signal strength during transmission). Mountains, hills and rooftops provide inexpensive and accessible bases for microwave transmission towers.

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1.10 Limitations With the development of satellite and cellular technologies, microwave has become less widely used in the telecommunications industry. Fiber-optic communication is now the dominant data transmission method. However, microwave communication equipment is still in use at many remote sites where fiber-optic cabling cannot be economically installed. The limitations of microwave communications are as follows:

• Line-of-sight will be disrupted if any obstacle, such as new buildings, are in the way

• Signal absorption by the atmosphere. Microwaves suffer from attenuation due to atmospheric conditions

• Towers are expensive to build

1.10.1 Line of Sight Technology

Microwave radio systems are a line of sight technology, meaning the signals will not pass through objects (e.g., mountains, buildings and airplanes). This drawback limits microwave communication systems to line of sight operating distances. Signals flow between one fixed point to another, provided no solid obstacle disrupts the flow.

1.10.2 Subject to Electromagnetic and Other Interference

According to "Rural America at the Crossroads: Networking for the Future," microwave radio signals are affected by electromagnetic interference (EMI). EMI is any disturbance that degrades, obstructs or interrupts the performance of microwave signals. Microwave signal disruption EMI is caused by electric motors, electric power transmission lines, wind turbines, television/radio stations and cell phone transmission towers. Wind turbines, for instance, scatter and diffract TV, radio and microwave signals when placed between signal transmitters and receivers. Microwave radio communication is also affected by heavy moisture, snow, vapor, rain and fog due to rain fade (the absorption of microwave signals by ice, snow or rain, causing signal degradation and distortion). …………………………………………………………………………………………….

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Chapter 2

Antenna Basics

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Chapter-02 Antenna Basics 2.1 Antenna Basics:

2.1.1 What is Antenna? :

An antenna is a conductor that can transmit, send and receive signals such as microwave, radio or satellite signals. A high-gain antenna increases signal strength, where a low-gain antenna receives or transmits over a wide angle. In other words : An antenna is a specialized transducer that converts radio-frequency (RF) fields into alternating current (AC) or vice-versa or a device used for radiating or receiving radio waves. Antenna is also known as aerial. Any one of the paired segmented, and movable sensory appendages occurring on the heads of many arthropods.There are two basic types: the receiving antenna, which intercepts RF energy and delivers AC to electronic equipment, and the transmitting antenna, which is fed with AC from electronic equipment and generates an RF field.

2.1.2 Basic Types of Antenna:

There are two basic types: 1. Receiving antenna 2. Transmitting antenna

Receiving antenna: This is which intercepts RF energy and delivers AC to electronic equipment. Fig 2.1: Receiving Antenna The receiver is represented by its input impedance as seen from the antenna terminals (i.e. transformed by the transmission line). Transmitting antenna: It’s an antenna which is fed with AC from electronic equipment and generates an RF field. Fig 2.2: Transmitting Antenna

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The transmitter is represented by its input impedance (which is frequency-dependent and is influenced by objects nearby) as seen from the generator.

Fig 2.3: Propagation of TEM wave using transmitting & receiving antenna Except this basis two types there are many antennas in our communication system. Such as: Horn antenna, monopole antenna,band antenna,long wire antenna,corner antenna,refletor antenna,cubical quad antenna,rhombic antenna,plasma antenna,mobile phone detetor antenna,GPS antenna,groundplane antenna,metal-plate antenna,liquid metal antenna,yagi antenna.

2.2 Basics Parameter of Antenna: Basic parameter of antenna includes the radiation patterns, gain, directivity, beam lob, beam width etc. 2.2.1 Radiation pattern: The radiation pattern of antenna is a representation (pictorial or mathematical) of the distribution of the power out-flowing (radiated) from the antenna (in the case of transmitting antenna), or inflowing (received) to the antenna (in the case of receiving antenna) as a function of direction angles from the antenna. • Antenna radiation pattern (antenna pattern): – is defined for large distances from the antenna, where the spatial (angular) distribution of the radiated power does not depend on the distance from the radiation source – is independent on the power flow direction: it is the same when the antenna is used to transmit and when it is used to receive radio waves – is usually different for different frequencies and different polarizations of radio wave radiated/ received

The Basic equation of radiation may be expressed simply as

ÍL=Qú (Ams-1 )

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Where, Í=Time-changing current, As-1

L=Length of current element, m Q=Charge, C Ú=Time change of velocity which equals the acceleration of the charge, ms-2

2.2.2 Gain:

Antenna gain relates the intensity of an antenna in a given direction to the intensity that would be produced by a hypothetical ideal antenna that radiates equally in all directions (isotropically) and has no losses. The gain is a measure of how much of the input power is concentrated in a particular direction. It is expressed with respect to a hypothetical isotropic antenna, which radiates equally in all directions. Thus in the direction (q, f), the gain is G (q, f) = (dP/dW)/ (Pin /4p) Where Pin is the total input power and dP is the increment of radiated output power in solid angle dW. The gain is maximum along the boresight direction. The input power is Pin = Ea

2 A / h Z0 where Ea is the average electric field over the area A of the aperture, Z0 is the impedance of free space, and h is the net antenna efficiency. The output power over solid angle dW is dP = E2 r2 dW/ Z0, where E is the electric field at distance r. But by the Fraunhofer theory of diffraction, E = Ea A / r l along the boresight direction, where l is the wavelength. Thus the boresight gain is given in terms of the size of the antenna by the important relation as G = h (4 p / l2) A This equation determines the required antenna area for the specified gain at a given wavelength. The net efficiency h is the product of the aperture taper efficiency ha, which depends on the electric field distribution over the antenna aperture (it is the square of the average divided by the average of the square), and the total radiation efficiency h * = P/Pin associated with various losses. These losses include spillover, ohmic heating, phase nonuniformity, blockage, surface roughness, and cross polarization. Thus h = ha h *. For a typical antenna, h = 0.55.

2.2.3 Directivity:

Directivity (D): the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions. D (θ,φ) = U(θ,φ)/Uavg = 4πU(θ,φ)/Prad

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The directivity of an isotropic radiator is D (θ,φ) = 1. The maximum directivity is defined as [D (θ,φ)]max = Do. The directivity range for any antenna is 0≤D (θ,φ)≤Do. Directivity in dB: D(θ,φ) [dB] = 10log10d(θ,φ)

2.2.4 Beamwidth:

The beamwidth is a measure of how much the frequency can be varied while still obtaining an acceptable VSWR (2:1 or less) and minimizing losses in unwanted directions. Half-power beamwidth (HPBW): Half-power beamwidth is the angle between two vectors from the pattern’s origin to the points of the major lobe where the radiation intensity is half its maximum First-null beamwidth (FNBW): First-null beamwidth is the angle between two vectors, originating at the pattern’s origin and tangent to the main beam at its base. Often FNBW ≈ 2*HPB

2.2.5 VSWR:

The Voltage Standing Wave Ratio (VSWR) is an indication of the amount of mismatch between an antenna and the feed line connecting to it. The range of values for VSWR is from 1 to ∞. A VSWR value under 2 is considered suitable for most antenna applications. The antenna can be described as having a good match.

2.2.6 Radiation Intensity:

The power radiated from an antenna per unit solid angle is called the radiation intensity U (watts per steradian or per square degree). The normalized power pattern can also be expressed in terms of this parameter as the ratio of the radiation intensity U(θ, φ), as a function of angle, to its maximum value. Thus,

Pn(θ, φ) = U(θ, φ)/U(θ, φ)max = S(θ, φ)/S(θ, φ)max Whereas the Poynting vector S depends on the distance from the antenna (varying inversely as the square of the distance), the radiation intensity U is independent of the distance, assuming in both cases that we are in the far field of the antenna.

2.2.7 Beam Efficiency:

The (total) beam area ΩA (or beam solid angle) consists of the main beam area (or solid angle) ΩM plus the minor-lobe area (or solid angle) Ωm. Thus, ΩA = ΩM + Ωm

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The ratio of the main beam area to the (total) beam area is called the (main) beam efficiency εM. Thus, Beam efficiency = εM = ΩM/ΩA (dimensionless) The ratio of the minor-lobe area (_m) to the (total) beam area is called the stray factor. Thus, Stray Factor =ε m = Ωm/ΩA

It follows that, ε M + ε m = 1

2.3 Antenna Patterns:

2.3.1 Antenna Pattern:

A graphical representation of the antenna radiation properties as a function of position (spherical coordinates). Common Types of Antenna Patterns

• Power Pattern - normalized power vs. spherical coordinate position. • Field Pattern - normalized /E/ or /H/ vs. spherical coordinate position.

2.3.2 Antenna Field Types:

• Reactive field - the portion of the antenna field characterized by standing (stationary) waves which represent stored energy.

• Radiation field - the portion of the antenna field characterized by radiating (propagating) waves which represent transmitted energy.

2.3.3 Antenna Field Regions:

• Reactive Near Field Region - the region immediately surrounding the antenna where the reactive field (stored energy – standing waves) is dominant.

• Near-Field (Fresnel) Region - the region between the reactive nearfield and the far-field where the radiation fields are dominant and the field distribution is dependent on the distance from the antenna.

• Far-Field (Fraunhofer) Region - the region farthest away from the antenna where the field distribution is essentially independent of the distance from the antenna (propagating waves).

2.3.4 Antenna Pattern Definitions:

• Isotropic Pattern - an antenna pattern defined by uniform radiation in all directions, produced by an isotropic radiator (point source, a non-physical antenna which is the only nondirectional antenna).

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• Directional Pattern - a pattern characterized by more efficient radiation in one direction than another (all physically realizable antennas are directional antennas).

• Omnidirectional Pattern - a pattern which is uniform in a given plane.

2.3.5 Principal Plane Patterns:

The E-plane and H-plane patterns for a linearly polarized antenna: • E-plane - the plane containing the electric field vector and the direction of

maximum radiation. • H-plane - the plane containing the magnetic field vector and the direction of

maximum radiation.

2.3.6 Antenna Pattern Parameters

• Radiation Lobe - a clear peak in the radiation intensity surrounded by regions of weaker radiation intensity.

• Main Lobe (major lobe, main beam) - radiation lobe in the direction of maximum radiation.

• Minor Lobe - any radiation lobe other than the main lobe. • Side Lobe - a radiation lobe in any direction other than the direction(s) of

intended radiation. • Back Lobe - the radiation lobe opposite to the main lobe.

Fig 2.4: Antenna Pattern Parameters (Normalized Power Pattern)

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2.4 Different types of antenna with their radiation patterns & characteristic: Some different types of antenna with their radiation patterns and characteristics are given below: 1. Monopole Antenna:

Fig 2.5: Monopole Antenna Radiation Pattern: Fig 2.6(a): Elevation Fig 2.6(b): Azimuth Characteristics: Polarization: Linear, vertical as shown Typical Half-Power Beamwidth: 45 deg x 360 deg Typical Gain: 2-6 dB at best Remarks: Polarization changes to horizontal if rotated to horizontal.

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2. λ/2 Dipole Antenna: Fig 2.7: λ/2 Dipole Antenna Radiation Pattern: Fig 2.8(a): Elevation Fig 2.8(b): Azimuth Characteristics: Polarization: Linear, vertical as shown Typical Half-Power Beamwidth: 80 deg x 360 deg Typical Gain: 2 dB Remarks: Pattern and lobing changes significantly with L/f. Used as a gain reference < 2 GHz.

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3. Biconical Antenna:

Fig 2.9: Biconical Antenna

Radiation Pattern:

Fig 2.10(a): Elevation Fig 2.10(b): Azimuth

Characteristics: Polarization: Linear, Vertical as shown Typical Half-Power Beamwidth: 20-100 deg x 360 deg Typical Gain: 0-4 dB

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4. Yagi Antenna:

Fig 2.11: Yagi Antenna Radiation Pattern: Fig 2.12(a): Elevation Fig 2.12(b): Azimuth Characteristics: Polarization: Linear, horizontal as shown Typical Half-Power Beamwidth: 50 deg X 50 deg Typical Gain: 5 to 15 dB

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5. Horn Antenna:

Fig 2.13 Horn antenna Radiation Pattern: Fig 2.14(a): Elevation Fig 2.14(b): Azimuth Characteristics: Polarization: Linear Typical Half-Power Beamwidth: 40 deg x 40 deg Typical Gain: 5 to 20 dB ………………………………………………………………………………………….....

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Chapter 3

Introduction of HFSS

and

Modeling of Dipole antenna

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Chapter-03: Introduction of HFSS and Modeling of Dipole antenna 3.1-What is HFSS? HFSS is a high-performance full-wave electromagnetic (EM) field simulator for arbitrary 3D volumetric passive device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates simulation, visualization, solid modeling, and automation in an easy-to-learn environment where solutions to your 3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM), adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of your 3D EM problems. Ansoft HFSS can be used to calculate parameters such as SParameters, Resonant Frequency, and Fields. Typical uses include:

1. Package Modeling – BGA, QFP, Flip-Chip 2. PCB Board Modeling – Power/Ground planes, Mesh Grid Grounds, 3. Backplanes 4. Silicon/GaAs - Spiral Inductors, Transformers 5. EMC/EMI – Shield Enclosures, Coupling, Near- or Far-Field Radiation 6. Antennas/Mobile Communications – Patches, Dipoles, Horns, Conformal 7. Cell Phone Antennas, Quadrafilar Helix, Specific Absorption Rate(SAR), 8. Infinite Arrays, Radar Cross Section(RCS), Frequency Selective Surfaces(FSS) 9. Connectors – Coax, SFP/XFP, Backplane, Transitions 10. Waveguide – Filters, Resonators, Transitions, Couplers 11. Filters – Cavity Filters, Microstrip, Dielectric

HFSS is an interactive simulation system whose basic mesh element is atetrahedron. This allows you to solve any arbitrary 3D geometry, especially those with complex curves and shapes, in a fraction of the time it would take using other techniques. The name HFSS stands for High Frequency Structure Simulator. Ansoft pioneered the use of the Finite Element Method (FEM) for EM simulation by developing/implementing technologies such as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep (ALPS). Today, HFSS continues to lead the industry with innovations such as Modes-to-Nodes and Full-Wave Spice™. Ansoft HFSS has evolved over a period of years with input from many users and industries. In industry, Ansoft HFSS is the tool of choice for high-productivity research, development, and virtual prototyping.

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3.2: Installing HFSS software

3.2.1-System Requirements

• Microsoft Windows XP, Windows 2000, or Windows 2003 Server. For

upto-date information, refer to the HFSS Release Notes. • Pentium –based computer • 128MB RAM minimum • 8MB Video Card minimum • Mouse or other pointing device • CD-ROM drive.

3.2.2- Installing the Ansoft HFSS Software

For up-to-date information, refer to the HFSS Installation Guide.

3.2.3- Starting Ansoft HFSS

• Click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 9

program group program group. Click HFSS 9. • Or Double click on the HFSS 9 icon on the Windows Desktop.

3.3-Ansoft Terms The Ansoft HFSS window has several optional panels:

• A Project Manager which contains a design tree which lists the structure of the project

• A Message Manager that allows you to view any errors or warnings that occur before you begin a simulation

• A Property Window that displays and allows you to change model • Parameters or attributes. • A Progress Window that displays solution progress. • A 3D Modeler Window which contains the model and model tree for the • Active design.

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Fig:3.1Differents terms of ansoft

3.3.1-Project Manager-

Fig:3.2 Differents terms of Project window

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Model

Graphics Area

3D modeler Design tree Context

menu

3.3.2-Property window

Fig:3.2 Differents terms of Property window

3.3.3-Ansoft 3D Modeler-

Fig:3.2(a)Different terms of 3D modeler window

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Fig:3.2(b)Different terms of 3D model

3.3.4-3D Modeler Design Tree

(a)Grouped by Materials (b)Object view

Fig:3.3 Modeler design tree

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3.3.6-Toolbars

• The toolbar buttons are shortcuts for frequently used commands. Most of the

available toolbars are displayed in this illustration of the Ansoft HFSS initial screen, but your Ansoft HFSS window probably will not be arranged this way.

• You can customize your toolbar display in a way that is convenient for you. Some toolbars are always displayed; other toolbars display automatically when you select a document of the related type. For example, when you select a 2D report from the project tree, the 2D report toolbar displays.

Fig:3.4 Toolbars of ansoft HFSS

3.3.7-Ansoft HFSS Desktop

The Ansoft HFSS Desktop provides an intuitive, easy-to-use interface for developing passive RF device models. Creating designs, involves the following:

• Parametric Model Generation – creating the geometry, boundaries and • excitations • Analysis Setup – defining solution setup and frequency sweeps • Results – creating 2D reports and field plots • Solve Loop - the solution process is fully automated • To understand how these processes co-exist, examine the illustration shown • Below

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Design

Solution type

1.Parametric modelGeometry/Materials

2.AnalysisSolution setup

Frequency sweep

3.Results2D reportsfields

Boundaries

Excitations

Analyze

Update

Mesh operation

Mesh refinement Solve

Converged

Finished

Fig:3.5 Ansoft desktop design tree.

3.5-Set Solution Type This section describes how to set the Solution Type. The Solution Type defines the type of results, how the excitations are defined, and the convergence. The following Solution Types are available:

• Driven Modal - calculates the modal-based S-parameters. The S-matrix solutions will be expressed in terms of the incident and reflected powers of

waveguide modes. • Driven Terminal - calculates the terminal-based S-parameters of

multiconductor transmission line ports. The S-matrix solutions will be expressed in terms of terminal voltages and currents.

• Eignemode – calculate the eigenmodes, or resonances, of a structure. The Eigenmode solver finds the resonant frequencies of the structure and the fields at those resonant frequencies.

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3.6-Parametric Model Creation:

• The Ansoft HFSS 3D Modeler is designed for ease of use and flexibility. Thepower of the 3D Modeler is in its unique ability to create fully parametric designswithout editing complex macros/model history.

• The purpose of this chapter is to provide an overview of the 3D Modeling capabilities. By understanding the basic concepts outlined here you will be ableto quickly take advantage of the full feature set offered by the 3D ParametricModeler.

3.6.1-Overview of the 3D Modeler User Interface (Continued)

When using the 3D Modeler interface you will also interact with two additional interfaces: Status Bar/Coordinate Entry – The Status Bar on the Ansoft HFSS Desktop Window displays the Coordinate Entry fields that can be used to define points or offsets during the creation of structural objects.

Fig:3.6 Status bar Grid Plane To simplify the creation of structural primitives, a grid or drawing plane is used.The drawing plane does not in any way limit the user to two dimensional coordinates but instead is used as a guide to simplify the creation of structural primitives. The drawing plane is represented by the active grid plane (The grid does not have to be visible). To demonstrate how drawing planes are used, review the following section: Creating and Viewing Simple Structures. Active Cursor

• The active cursor refers to the cursor that is available during object creation. The cursor allows you to graphically change the current position. The position is displayed on the status bar of the Ansoft HFSS Desktop Window

Fig:3.7Active Cursor

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• When objects are not being constructed, the cursor remains passive and is set for

dynamic selection. See the Overview of Selecting Objects for more details.

3.7-The Dipole Antenna simulation by HFSS V.9 Dipole antennas are extremely popular in the microwave region. Dipole antennas are commonly used for broadcasting, cellular phones, and wireless communications due to their omnidirective property. Thus in this tutorial, a dipole antenna will be constructed and analyzed using the HFSS in this simulation.

3.7.1-Getting started with HFSS 9.1:

• Launching Ansoft HFSS

To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 9 program group. Click HFSS 9.

• Setting Tool Options § To set the tool options:

Note: In order to follow the steps outlined in this example, verify that the following tool options are set: 1. Select the menu item Tools>Options> HFSS Options 2. HFSS Options Window:

1. Click the General tab Use Wizards for data entry when creating new

boundaries:Checked Duplicate boundaries with geometry: Checked

2. Click the OK button 3. Select the menu item Tools > Options > 3D Modeler

Options. 4. 3D Modeler Options Window: 1. Click the Operation tab Automatically cover closed polylines: _ Checked 2. Click the Drawing tab Edit property of new primitives: _ Checked 3. Click the OK button

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3.7.2-Opening a New Project

To open a new project:

1. In an Ansoft HFSS window, click the _ On the Standard toolbar, or select the menu item File > New.

2. From the Project menu, select Insert HFSS Design.

Fig:3.8 Project menu window Set Solution Type

To set the solution type: 1. Select the menu item HFSS > Solution Type

2. Solution Type Window: 1. Choose Driven Modal 2. Click the OK button

Fig: 3.9 Solution type window

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3.7.3-Creating the 3D Model

Set Model Units

To set the units: 1. Select the menu item 3D Modeler > Units 2. Set Model Units: 1. Select Units: mm 2. Click the OK button

Fig. 3.10 Model Unit window Set Default Material To set the default material: Using the 3D Modeler Materials toolbar, choose vacuum

Fig. 3.11 set the default material

3.8-Create Dipole

3.8.1-Create waveguide

HFSS relies on variables for any parameterization / optimization within the project. Variables also hold many other benefits which will make them necessary for all projects.

• Fixed Ratios (length, width, height) are easily maintained using variables.

• Optimetrics use variables to optimize the design according to user-defined criteria.

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• All dimensions can be quickly changed in one window as opposed to altering each object individually.

This will open the variable table. Add all variables shown below by selecting Add. Be sure to include units as needed. Fig. 3.12 Property window

The final variable table should looks like

Fig. 3.13 Final variable table

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3.8.2- Drawing the Dipole

• We will start to by creating the dipole element using the Draw Cylinder button

from the toolbar.

• By default the proprieties dialog will appear after you have finished drawing an object. The position and size of objects can be modified from the dialog.

Fig. 3.14 Drawing dipole

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Fig. 3.15 appeared table by creating the dipole

• Double click to the model menu and this will appear a window like as follow Fig. 3.16 table from model menu

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• Follow the format above for structure size. Give the name dip1 to this object. Assign the material PEC and click OK. PEC (Perfect Electric Conductor) will create ideal conditions for the element.

The next step is to build the symmetric of dip1. To do that, Right -Click the drawing area and select Edit -> Duplicate -> Around Axis.

Fig. 3.17 form the duplicate dipole in the 180 degree position

Fig. 3.18 Duplicate Around Axis window

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The dipole structure is illustrated below: Fig. 3.19 Final dipole structure

3.9- Creating the port

• In the section you will create a Lumped Gap Source. This will provide an excitation to the dipole structure. Begin by selecting the YZ plane from the toolbar. Using the 3D toolbar, click Draw Rectangle and place two arbitrary points within the model area.

Fig:3.20 (a) Selecting YZ plane Fig: 3.20(b) Draw rectangle

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Enter the following information

Fig. 3.21 Property window Double click “create rectangle’’ and this will appear a window like below.

Fig. 3.22 View of a 3D modeler window

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Enter the information below

Fig. 3.23 Property window

• With the source geometry in place, the user must provide an excitation. A lumped port will be used for the dipole model. This excitation is commonly used when the far field region is of primary interest. In the project explorer, right-click Excitation -> Assign -> Lumped Port.

Name the port source and leave the default values for impedance. Name the port source and leave the default values for impedance

Fig. 3.24 Port assumption

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Click Next and enter the following:

Fig. 3.25 Port assigning window

Using the mouse, position the cursor to the bottom-center of the port. Ansoft's snap feature should place the pointer when the user approaches the center of any object. Left-click to define the origin of the E-field vector. Move the cursor to the top-center of the port. Left-click to terminate the E-field vector. Click finish to complete the port excitation. Note: In case you find some difficulties for drawing the lumped port, you can redraw the rectangular plane, affect the lumped port, then resize the rectangular plane.

Fig. 3.26 HFSS window after assigning port

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3.10- Radiation Boundary In this section, a radiation boundary is created so that far field information may be extracted from the structure. To obtain the best result, a cylindrical air boundary is defined with a distance of λ/4. From the toolbar, select Draw Cylinder. Enter the following information:

Fig. 3.27 Property window

Fig. 3.28 Property window

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• With the geometry complete, the actual radiation boundary may now be assigned.

• Click and select all faces as follow:

Fig:3.29 Select Face Window

• With all faces selected, right-click the Boundary icon in the object explorer and

select Boundary -> Assign -> Radiation. Leave the default name Rad1 and click OK.

Fig:3.30 Select Radiation port

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3.11- Solution Setup In this section a solution must be defined to display the desired data. We are primarily interested in the frequency response of the structure. We will also explore HFSS's ability to calculate general antenna parameters such as directivity, radiation resistance, radiation efficiency, etc... . From the project explorer, select Analysis -> Add Solution Setup. Enter the following. Click ok when complete.

Fig:3.31 Select Setup window To view the frequency response of the structure, a frequency sweep must be defined. From the project explorer select Setup1 -> Add Sweep.

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Enter the following:

Fig:3.32 Select Setup window

3.12- Structure Analysis At this point, the user should be ready to analyze the structure. Before running the analysis, always verify the project by selecting from the 3D toolbar. If everything is correct the user should see:

Fig:3.33 Validation Check Window

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Analyze the structure by clicking

Fig. 3.34 Analyzing window

3.13- Create Reports

Ø After completion of the analysis, we will create a report to display both the resonant frequency and also the radiation pattern. Click on the heading HFSS and select Results -> Create Reports.

Choose the following in the Create Report window:

Fig. 3.35 Select the result patterns

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• Select the following highlighted parameters and click Add Trace to load the options into the Trace window.

Fig:3.36 Trace Window

• Click Done when complete. The graph is displayed below:

Fig. 3.37 Rectangular plot

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• HFSS has the ability to compute antenna parameters automatically. In order to

produce the calculations, the user must define an infinite sphere for far field calculations. Right-click the Radiation icon in the project manager window and select Insert Far Field Setup -> Infinite Sphere.

(a) (b)

Fig. 3.38 (a) Define the air box as infinite sphere; (b) Compute antenna properties

• Accept all default parameters and click Done. Right-click Infinite Sphere1 -

>Compute Antenna Parameters... from the project explorer as shown: • Select all defaults and results are displayed as follows:

Fig: 3.39 Results of antenna parameters

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• Next, the far field will be plotted. Create Reports as previously shown. Modify the following:

Fig: 3.40 Display type

• Enter the following:

Fig. 3.41 Traces Window

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• Select the Mag and enter the following:

Fig. 3.42 Traces Window

• Select Add Trace and click Done when complete. The radiation pattern is

displayed below:

Fig. 3.43 Radiation pattern of Directivity

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Chapter 4

Parametric Study of

Horn Antenna

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Chapter 4: Parametric Study: Horn Antenna

Horn antennas are extremely popular in the microwave region. An aperture antenna contains some sort of opening through which electromagnetic waves are transmitted or received. One of the examples of aperture antenna is horns. The analysis of aperture antennas is typically quite different than the analysis of wire antennas. Before the parametric study here we discussed about different types of horn antennas

4.1: Types of Horn Antennas Generally Horn Antenna is type of waveguide one end of which is flared out. Flared waveguide, which produces nearly uniform phase front, is larger than the waveguide itself. However, radiation is poor and non directive pattern results because of mismatch between the waveguide and free space. The mouth of the waveguide is flared out to improve the radiation efficiency, directive pattern and directivity.

There are three main basic types of Horn Antennas:

1. Sectoral Horn 2. Pyramidal Horn 3. Conical Horn

• Sectoral Horn is two types: a. Sectoral H-plane Horn b. Sectoral E-plane Horn

Fig: 4.1 H-plane sectoral horn Fig: 4.2 E-plane sectoral horn

Fig: 4.3 Pyramidal horn Fig: 4.4 Conical horn

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The pyramidal horn is the most widely used antenna for feeding large microwave dish antennas and for calibrating them. That’s why we are simulating a pyramidal horn antenna here.

4 . 2: Horn antenna parameters

In this simulation, our objective is to analyze a horn antenna resonating at a frequency of 10 GHz.

Here are the dimensions of Horn Antenna: • Wave guide dimension: a = 22.86mm & b = 10.16mm • Horn top: 60mm * 45mm • Distance from the horn top plane to the bottom is 120mm • Distance from the top plane to the base of waveguide of the horn is 132mm • Air box: 145mm * 70mm * 50mm

4.3: Modeling of Horn antenna in HFSS

4.3.1: Getting started with HFSS 9.1:

• Launching Ansoft HFSS

To access Ansoft HFSS, click the Microsoft Start button, select Programs, and select the Ansoft, HFSS 9 program group. Click HFSS 9.

• Setting Tool Options • To set the tool options:

Note: In order to follow the steps outlined in this example, verify that the following tool options are set:

1. Select the menu item Tools>Options> HFSS Options 2. HFSS Options Window:

1. Click the General tab Use Wizards for data entry when creating new boundaries: Checked

Duplicate boundaries with geometry: Checked

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2. Click the OK button 3. Select the menu item Tools > Options > 3D Modeler Options.

4. 3D Modeler Options Window:

1. Click the Operation tab Automatically cover closed poly lines: _ Checked

2. Click the Drawing tab Edit property of new primitives: _ Checked

3. Click the OK button

4.3.2: Opening a New Project

• To open a new project:

1. In an Ansoft HFSS window, click the On the Standard toolbar, or select the menu item File > New. 2. From the Project menu, select Insert HFSS Design.

• Set Solution Type • To set the solution type:

1. Select the menu item HFSS > Solution Type 2. Solution Type Window:

1. Choose Driven Modal 2. Click the OK button

Fig: 4.5 Project menu window Fig: 4.6 Solution type window

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4.3.3: Creating the 3D Model

• Set Model Units To set the units:

1. Select the menu item 3D Modeler > Units 2. Set Model Units:

1. Select Units: mm 2. Click the OK button

Fig. 4.7 Model Unit window

• Set Default Material

• To set the default material: Using the 3D Modeler Materials toolbar, choose vacuum

• Create Rectangular Waveguide

• Create waveguide 1. Select the menu item Draw > Box 2. Using the coordinate entry fields, enter the Box position

X: -11.43, Y: -5.08, Z: 0.0 Press the Enter key 3. Using the coordinate entry fields enter the ‘a’ and ‘b’:

dX: 22.86, dY: 10.16, dZ: 0.0 Press the Enter key 4. Using the coordinate entry fields, enter the height:

dX: 0.0, dY: 0.0, dZ: 8.0 Press the Enter key

Fig. 4.8 Waveguide

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• To set the name:

1. Select the Attribute tab from the Properties window. 2. For the Value of Name type: Waveguide 3. Click the OK button

• To fit the view:

1. Select the menu item View > Fit All > Active View. Or press the CTRL+D key

• To make the waveguide transparent:

1. Select the Attribute tab from the Properties window. 2. For the Transparent click and type: 0.5 and Click OK. 3. Click the OK button.

4.3.4: Create Horn Top

• Create rectangle:

1. Select the menu item Draw > Rectangle 2. Using the coordinate entry fields, enter the Rectangle position

X: -30.0, Y: -22.5, Z: 140.0 Press the Enter key 3. Using the coordinate entry fields, enter the horn top dimension:

dX: 60.0, dY: 45.0, dZ: 0.0 Press the Enter key

• To set the name:

1. Select the Attribute tab from the Properties window. 2. For the Value of Name type: Horn_top 3. Click the OK button

• To fit the view: 1. Select the menu item View > Fit All > Active View. Or press the CTRL+D key

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4.3.5: Create funnel base:

To create the funnel of the horn antenna, draw and connect two rectangles, and then connect them to create the 3D funnel. First rectangle is horn top. Now place the second on the top of the waveguide.

• Create Rectangle:

1. Select the menu item Draw > Rectangle 2. Using the coordinate entry fields, enter the Rectangle position

X: -11.43, Y: -5.08, Z: 8.0 Press the Enter key 3. Using the coordinate entry fields, enter the horn top dimension:

dX: 22.86, dY: 10.16, dZ: 0.0 Press the Enter key

• To set the name:

1. Select the Attribute tab from the Properties window. 2. For the Value of Name type: funnel_base 3. Click the OK button

4. To select the Color click Edit.

5. Choose the Green and click Ok.

Fig. 4.9 Waveguide and Funnel Base

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4.3.6: Create the funnel:

• Connecting 2D Objects:

Now you can connect the 2D objects that make up the base and the top of the funnel to create the 3D, funnel-shaped object.

1. Choose the Horn_Top and funnel_base from the 3D Modeler design tree.

2. Select the menu item 3D Modeler > Surface > Connect.

3. Name the object funnel.

Fig. 4.10 Project menu Fig. 4.11 Highlight the Horn top and funnel base

4.3.7: Complete the Horn

• To select the object

Select the menu item Edit > Select All Visible. Or press the CTRL+A key.

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Fig. 4.12 A complete horn after connection Fig. 4.13 A complete horn after unite

• To complete the horn

Select the menu item, 3D Modeler > Boolean > Unite.

4.3.8: Create Air Box around the Horn Antenna

• Create Air Box

1. Select the menu item Draw > Box 2. Using the coordinate entry fields, enter the Box position

X: -35.0, Y: -25.0, Z: 0.0 Press the Enter key 3. Using the coordinate entry fields enter the a and b:

dX: 70.0, dY: 50.0, dZ: 0.0 Press the Enter key 4. Using the coordinate entry fields, enter the height:

dX: 0.0, dY: 0.0, dZ: 145.0 Press the Enter key

• To set the name

1. Select the Attribute tab from the Properties window. 2. For the Value of Name type: Air 3. Click the OK button

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• To fit the view: 1. Select the menu item View > Fit All > Active View.

Or press CTRL+D.

Fig. 4.14 An Air box outside the horn

4.3.9: Assigning Boundaries and excitations

• Create wave port

1. Select the menu item Edit > Select > Faces. 2. Select the Edit > Select > By name. 3. Select the Base > Face 8(Bottom face).

Fig. 4.15 Select Face window

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• To assign wave port excitation

Assign Excitation to the bottom face of the horn.

1. Right Click > Assign Excitation > Wave port

2. Name it WavePort1.

Fig. 4.16 Wave Port

4.3.10: Create Radiation Boundary

• To create a radiation boundary

1. Select the menu item Edit > Select > By Name 2. Select Object Dialog,

1. Select the objects named: Air 2. Click the OK button

3. Select the menu item HFSS > Boundaries > Assign> Radiation 4. Radiation Boundary window

1. Name: Rad1 2. Click the OK button.

• To Create a perfect electric field boundary

1. Select the menu item Edit > Select > By Name 2. Select Object Dialog,

1. Select the objects named: Base 2. Click the OK button

3. Select the menu item HFSS > Boundaries > Assign> Perfect E 4. Radiation Boundary window

1. Name: PerfE_horn_sides

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2. Click the OK button.

4.3.11: Analysis Setup

• To Create an analysis setup

1. Select the menu item HFSS > Analysis Setup > Add Solution Setup 2. Solution Setup Window:

1. Click the General tab: Solution Frequency: 10.0 GHz Maximum Number of Passes: 20 Maximum Delta S per Pass: 0.02

2. Click the OK button

• To create sweep setup

1. Select the menu item HFSS > Analysis Setup > Add sweep 2. Solution Setup Window Click OK:

1. Edit sweep window: Sweep type: Fast Type: Linear count Start: 8.4; Stop: 12.2; Count: 100.

2. Click the Display button and Click Ok.

Fig. 4.17 Solution setup window Fig: 4.18 Sweep setup window

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4.3.12: Model Validation

• To validate the model:

1. Select the menu item HFSS > Validation Check 2. Click the Close button.

Note: To view any errors or warning messages, use the Message Manager.

Fig. 4.19 Validation Check Window

4.3.13: Analyze

• To start the solution process:

1. Select the menu item HFSS > Analyze All

Fig. 4.20 Analyzing window

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4.4: Creating Report

4.4.1: Create 3D Polar Far Field Plot

v To create a 3D Far Field Plot

1. Select the menu item HFSS > Results > Create Report 2. Create Report Window:

1. Report Type: Far Fields 2. Display Type: 3D Polar Plot 3. Click the OK button

3. Traces Window: 1. Solution: Setup1: LastAdaptive 2. Domain: Radiation 3. Click the Mag tab

1. Category: rE 2. Quantity: rETotal 3. Function: dB 4. Click the Add Trace button

4. Click the Done button

Fig. 4.21 3D Polar plot

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4.4.2: Creating rectangular plot

• To Create Rectangular plot

1. Select the menu item HFSS > Results > Create Report

2. Create Report Window: 1. Report Type: Modal S Parameter 2. Display Type: Rectangular Plot 3. Click the OK button

3. Traces Window: 1. Category: S Parameter 2. Quantity: S(Wave Port 1,Wave Port 1) 3. Function: dB 4. Click the Add Trace button

4. Click the Done button

Fig. 4.22 Trace window

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Fig. 4.23 Rectangular plot

• To Create another Rectangular Plot

1. Select the menu item HFSS > Results > Create Report

2. Create Report Window: 1. Report Type: Modal S Parameter 2. Display Type: Rectangular Plot 3. Click the OK button

3. Traces Window: 1. Category: Z Parameter 2. Quantity: Z(Wave Port 1,Wave Port 1) 3. Function: re & im both 4. Click the Add Trace button for both

4. Click the Done button

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Fig. 4.24 Traces Window

Fig. 4.25 Rectangular plot for real and imaginary impedance of horn antenna

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4.5: Compute Antenna Parameter HFSS has the ability to compute antenna parameters automatically. In order to produce the calculations, the user must define an infinite sphere for far field calculations.

1. Right-click the Radiation icon in the project manager window 2. select Insert Far Field Setup 3. Right-click the Infinite Sphere 4. Select Compute Antenna Parameters 5. Antenna parameters window comes then click Ok

(a)

(b)

(c)

Fig. 4.26 (a) Define the air box as infinite sphere; (b) Compute antenna properties

(c) Results of antenna parameters

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4.6 Create animation of Electric field and Magnetic field • To create animation

1. Select Global:YZ plane form the planes in the design menu

2. Then select Field Overlays> Plot fields> Mag_E from the project menu window.

3. Create field plot window comes. Select default and click OK.

4. Go to Field Overlays> E-fields> Mag_E1. Click animate.

5. Click Ok.

6. With the same process the animation of magnetic field can be done.

(a) (b)

Fig. 4.27(a) Electric field propagation animation (b) Magnetic field propagation animation

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4.7 Simulation results of different types of Horn antenna Our aim was to build an affordable horn antenna for our university laboratory setup of microwave laboratory. Horn antennas are extremely popular in the microwave region. Horns provide high gain, low VSWR (with waveguide feeds), relatively wide bandwidth, and they are not difficult to make. There are three basic types of rectangular horns. We are concerned with the pyramidal horn antenna. But we simulated all the basic type of antennas, with computer aided engineering software HFSS, for comparing among them. The H-plane sectoral horn in which the long side of the wave guide is flared, the E-plane sectoral horn in which the short side is flared, and the pyramidal horn in which both sides are flared.

4.7.1 Simulation Results for H-plane sectoral Horn antenna

Dimensions of H-plane sectoral Horn:

• Horn Top: A = 69 and B = 10.16 • Wave guide: a = 22.86 b = 10.16 • Frequency: 10GHz

Fig. 4.28 H-plane sectoral horn

4.7.2 3D Polar plot for H-plane sectoral Horn:

In figure 4.29 showing the polar plot of H-plane

sectoral horn. It is wider because of its larger

dimension in the H - plane. So its directivity is

low for its narrow dimension.

Fig. 4.29 3D polar plot

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4.7.3 Antenna parameters of H-sectoral Horn:

Fig. 4.30 Antenna parameters of H-sectoral Horn

Directivity and Gain is very low of H-sectoral horn.

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4.7.4 Simulation Results for H-plane sectoral Horn antenna

Dimensions of E-plane sectoral Horn

• Horn Top: A = 22.86 and B = 49 • Wave guide: a = 22.86 b = 10.16 • Frequency: 10GHz

Fig. 4.31 E-plane sectoral horn

4.7.5 3D Polar plot for E-plane sectoral Horn:

In figure 4.32 showing the polar plot of E-plane

sectoral horn. It is narrow because of its narrow

dimension in the H - plane. So its directivity is

also low for its narrow dimension.

Fig. 4.32 3D polar plot

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4.7.6 Antenna parameters of H-sectoral Horn:

Fig. 4.33 Antenna parameters of E-sectoral Horn

Directivity and Gain is also very low of E-sectoral horn.

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4.7.7 Simulation Results for Pyramidal Horn antenna

Dimensions of Pyramidal Horn

• Horn Top: A = 67 and B = 49 • Wave guide: a = 22.86 b = 10.16 • Frequency: 10GHz

Fig: 4.34 Pyramidal horn

4.7.8 3D Polar plot for E-plane sectoral Horn:

In figure 4.35 showing the polar plot of pyramidal

horn. Its directivity and shape is perfect and very

similar to the ideal polar plot.

Fig. 4.35 3D polar plot

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4.7.9 Antenna parameters of Pyramidal Horn:

Fig. 4.36 Antenna parameters of Pyramidal Horn

So here we can see that, the directivity and gain of this pyramidal horn antenna is very high and close to our theoretical results. That’s why we choose this parameter for the hardware interpretation.

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4.7.10 Antenna as impedance matching device

Fig. 4.37 Impedance parameter of waveguide

Fig. 4.38Impedance parameter of pyramidal horn

• This is the impedance graph of the waveguide (WR90) we have used. Here value of real part is 550Ω when imaginary part is zero. So the maximum power will be transmitted when the impedance parameter of horn antenna will be very closer to this result. Our analysis result is given below in the figure. And it is closer to the value of waveguide.

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4.7.11 Rectangular plot and radiation pattern of Directivity and Gain

Fig. 4.39 Rectangular plot of Directivity

Fig. 4.40 Radiation pattern of Directivity

……………………………………………………………………………………….........

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Chapter 5

Implementation of Horn Antenna

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Chapter 5: Implementation of Horn Antenna In this chapter we will discuss the hardware implementation of horn antenna. We tested the antenna, which we have made, according to the parameter that we got from the software analysis. We only measured the gain of horn antenna. Our microwave test bench is Klystron based setup.

5.1 Equipments / Instruments

• Klystron power supply • Klystron mount • Isolator • Variable attenuator • Detector mount • Standard gain horn VSWR meter

Fig. 5.1 Measurement of Horn

5.2 Diagram of instruments setup

Fig. 5.2 Microwave bench set-up to measure the gain of horn antenna

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5.3 Procedure Here is the working procedure:

i. Set up the equipment as shown in Figure 5.1 and connect the tuner and crystal detector assembly to the slotted line.

ii. Switch on fan and then power supply. Obtain oscillations of the klystron.

iii. Set the variable attenuator to get convenient reading in the VSWR meter

iv. Maximize the crystal detector power supply and match the detector with the help

of the tuner.

v. Set a convenient reading on the indicator vi. Disconnect the tuner and detector assembly. Connect horn to the attenuator and

another horn to another attenuator and the detector assembly. Put the second horn in front of the first. The distance between horns should be about one.

vii. Read the VSWR meter and note the difference in two reading and measure the

separation‘s’ between two horns. viii. Repeat the same experiment for different values of separation between horns.

5.4 Tabular Column

Table 5.1 Experimental Results

Distance between horns in cm VSWR reading when horns are connected 50 48 60 46.8 70 46 80 44.5 90 41

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Gain Vs Distance Graph

48

46.8

46

44.5

41

40

41

42

43

44

45

46

47

48

49

0 20 40 60 80 100

Distance (cm)

Gain (dB)

5.5 Graphical Representation of the results

Fig. 5.3 Gain Vs Distance Graph

5.6 Snap shots of microwave test bench and Horn antenna

5.6.1 Microwave test bench

Fig. 5.3 Microwave test bench of UIU lab

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5.6.2 Horn antenna

Fig. 5.4 Pyramidal Horn antenna

Fig. 5.5 Microwave test bench when horn antenna is connected ……………………………………………………………………………………..

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Chapter 6

Conclusion

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Chapter 6 Conclusion The construction of the horn antennas was simple in terms of paper and pencil. However, fabrication was far more difficult than anticipated before we started the project, but we managed to construct the horn antennas and reach our goal. The resulted measured data supports our expected result. We successfully transmitted the wave via air with the help of horn antenna. Our data could have been improved if we had an adequate antenna testing facility accommodation. But we hope that, for this antenna, a new experiment will be added to microwave engineering laboratory. We are happy that finally we able to fulfill the demand of the students.

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References

• “Electromagnetic Wave and Antennas” by Sophocles J. Orphanidis • http://www.ece.rutgers.edu/~orfanidi/ewa/ • http://en.wikipedia.org/wiki/Microwave_transmission • http://en.wikipedia.org/wiki/Communications_satellite • http://en.wikipedia.org/wiki/Horn_antenna • http://www.q-par.com/products/horn-antennas • http://en.wikipedia.org/wiki/Antenna_(radio) • http://www.antenna-theory.com/antennas/aperture/horn.php • http://en.wikipedia.org/wiki/Dipole_antenna • http://www.ansoft.com/products/hf/ansoft_designer/ • http://www.educypedia.be/electronics/electroniccalculatorsant.htm • http://www.ansoft.com/products/hf/hfss/ • http://www.scribd.com/doc/16584538/HFSS-Tutorial • http://www.electronics-tutorials.com › ANTENNAS • http://www.radio-electronics.com › Antennas and propagation • http://www.wtec.org/loyola/satcom/toc.htm