2013 August 7 Microwave Radio Principles

7/27/2019 2013 August 7 Microwave Radio Principles

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41st Signal BattalionMaintenance Support Team

AN INTRODUCTION TO

Digital Microwave Principles

(DMR)

Mr. Thomas SamuelsU.S. Air Force

Space and Missile System Center Range Network Systems Upgrades (RNSU)

Peterson Air Force BaseColorado Springs, CO

[email protected]

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This course provides guidance for technicians and operators explaining Microwave BasicsPrinciples and Digital Microwave Communications, and how the Microwave BasicPrinciples apply to the Harris Megastar 155 Digital Microwave Radio commonly used bythe U.S. Army in the Republic of Korea.

Paving the way for learning how to maintain and providing trouble isolation techniques for the Harris Megastar 155 Digital Microwave Radio and associated Networking systems.

Microwave PrinciplesForeword 2


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Microwave PrinciplesLearning Guide

Microwave communication was developed with the basis of the electromagnetic field theory commonly called RadioFrequency propagation.

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After this course, you will be able to explain:Basic concepts and characteristics of a Digital Microwave Communication Systems

Functions and principles of each component of the Harris Megastar 155 Digital Microwave Radio andassociated Asynchronous Transfer Mode switching systems; commonly known as DigitalMultiplexers.

Common networking modes and application scenarios of Digital Microwave Communication asapplied to the Harris Megastar 155 Digital Microwave Radio

Propagation principles of Digital Microwave Communication and various types of fading

Anti-fading technologies

Microwave PrinciplesObjectives 4


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Microwave PrinciplesContents

1. Digital Microwave Communication Overview

2. Digital Microwave Communication Equipment

3. Digital Microwave Networking and Application

4. Microwave Propagation and Anti-fading Technologies

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Coaxial Cable Communication

MicrowaveCommunication

Optical Cable Communication

MuxDemux

MuxDemux

Microwave PrinciplesTransmission Methods in Current Communications Networks

SatelliteCommunication

M i c r o w a v e

T E

M i c r o w a v e

T E

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Microwave PrinciplesMicrowave Communication vs. Optical Fiber Communication

Microwave Communication

Powerful space cross ability, little landoccupied, not limited by land privatization

Small investment, short construction period,easy maintenance

Strong protection ability against natural disaster and easy to be recover

Limited frequency resources (frequency licenserequired)

Transmission quality greatly affected by climateand landform

Limited transmission capacity

Optical Fiber Communication

Optical fiber burying and land occupationrequired

Large investment ,long construction period

Outdoor optical fiber maintenance required andhard to recover from natural disaster

Not limited by frequency

license not required

Stable and reliable transmission quality and notaffected by external factors

Large transmission capacity

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Microwave PrinciplesDefinition of Microwave

Microwave is a type of electromagnetic wave. In a broad sense, the frequency range isfrom 300 MHz to 300 GHz. But In microwave communication, the frequency range isgenerally from 3 GHz to 30 GHz. The Microwave frequency used for transmission of digitaldata by the U.S. Army in the Republic of Korea is between 7 GHz and 8 GHz

According to the characteristics of microwave propagation, microwave frequencies can beconsidered as plane waves.

The plane wave has no electric field or magnetic field longitudinal components along thepropagation direction.

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Microwave PrinciplesDefinition of Digital Microwave

Digital microwave is a medium for transmitting digital information in the atmosphere through electronicmagnetic commonly called Radio Frequency (RF) waves.

Electromagnetic field theory is the basis on which microwave communication RF theory isdeveloped.

Microwave transmission refers to the communication that uses a microwave RF as carrier andadopts digital modulation techniques.

The baseband signal is modulated to an intermediate frequency (IF) first. Then heterodyned (mixed)with the microwave transmission frequency(RF).

NoteOnly phase shift key (PSK) modulation is applicable.

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Microwave PrinciplesDevelopment of Microwave Communication

480 voicechannels

2M 4M 6M

34M 140M

155MSDH digital microwavecommunication system

PDH digital microwavecommunication system

Small and medium capacitydigital microwavecommunication system

Analog microwavecommunication system

1950s

1970s

1980s

Late1990sto now

Transmission Capacity

NoteSmall Capacity < 10 Mbits/ChannelMedium Capacity 10 to 100 Mbits/ChannelLarge Capacity > 100 MBits/Channel

Mega Bits per Channel



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3.5

Regional Network

1.5 2.5

2 Mbits/sec8 Mbits/sec

34 Mbits/sec

Long Haul Trunk Network

Regional Network Local Network Boundary Network

2 Mbits/sec8 Mbits/sec

34 Mbits/sec140 Mbits/sec155 Mbits/sec

GHz

1 2 3 4 5 8 10 20 30 40 50

Microwave Radio Frequency used in by the U.S. Army in the Republic of Korea is 6 GHz to 8 GHz

10 10 10 11

6 7

Microwave PrinciplesDefinition of Digital Microwave

119

10 9 10 8 10 4 10 12 10 15 10 16 10 18 10 20

155 Mbits/sec

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1 x 1

0 9 1

G H z

6 x 1 0 9

6 G H z

2 x 1 0 9

2 G H z

3 x 1 0 9

3 G H z

4 x 1 0 9

4 G H z

5 x 1 0 9

5 G H z

7 x 1 0 9

7 G H z

8 x 1 0 9

8 G H z

9 x 1 0 9

9 G H z

1 0 x 1

0 9 1 0 G H z

Microwave PrinciplesMicrowave Radio Frequency Configuration

2 c m

3 c m

Microwave Radio Wave Length in Meters

1 c m

9 0 c m

8 0 c m

7 0 c m

6 0 c m

6 0 c m

4 c m

5 c m

(as defined by International Telecommunications Union radio spectrum (ITU-R) recommendations).

11 GHz,13 GHz,15 GHz,18 GHz

23 GHz26 GHz32 GHz38 GHz

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In each frequency band and frequency sub-band the transmit/receive (T/R spacing) and channel spacingare defined

Microwave PrinciplesMicrowave Radio Frequency Configuration - 2Frequency Band Selection and RF Channel Configuration

f 2 f 1 f n ChannelSpacing

Frequency Range

f c Center Frequency

Low Frequency Band High Frequency Band

T/R Spacing

T/R Spacing

ChannelSpacingf 1

f n f 2

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In each frequency band and frequency sub-band the transmit/receive (T/R spacing) and channel spacing aredefined

f 1 = 7442 MHz

T/R Spacing 154 Mbits

f 5 f 2

Microwave PrinciplesMicrowave Radio Frequency Configuration - 3Frequency Band Selection and RF Channel Configuration - 2

Frequency Range 7425 MHz 7725 MHzF c (7575 MHz)

28 Mbits

Frequency Range F c MHz T/R Spacing MHz Channel Spacing MHz Primary and Non-Primary Stations

7425 MHz 7725 MHz 7575 154 28 f n = f c 161 + 28n7575 161 7 f n = f c 7 + 28n (n:1-5)

7110 MHz 7775 MHz 7225 196 287597 196 28

7250 MHz 7550 MHz 7400 161 3.5

f 2 = 7470 MHz f 1 = 7596 MHz

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Transmission mediaCopper mediaMicrowave RadioOptical Fiber Infra Red Radio

Microwave radio terminal - three Basic Modules to interface with equipment and convert traffic to amodulated signal

Base Band (SPU)

Radio Frequency Unit (RFU) Antenna Coupling Unit ((ACU)IDUODU - (The IDU is connected to the ODU via the IF cable) not used.

Commonly used capacity configurations155 Mega Bits per Second

In the United States the basic Data Transfer Rate is a data stream 1.55 mbpsIn Europe the basic Data Transfer Rate is a data stream of 2.048 Mbps

Advantages Lower start up and operational cost

Synchronization Digital Hierarchy (SDH) is a technology used in telecommunication systems to transportlarge quantities of date over digital transport equipment such as microwave systems

In a SDH system every equipment is provide timing by an external timing source currently the industry is GPS timing.In a PDH system provides an internal clock generating its the synchronization.

Microwave PrinciplesDigital Microwave CommunicationModulation 1Characteristics and Advantages

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A device which varies a characteristic of a repetitious electrical or electromagnetic wave of less than infraredfrequency in accordance with a characteristic of an arbitrarily varying modulating signal.

Microwave PrinciplesMegastar 155 Microwave RadioModulation 2Modulation

Modulation defined - Addition of information (or signal) to an electronic or optical carrier.

Modulation can be applied to direct current (mainly by turning it on and off), to alternating current, or tooptical signals.

Example - think of a blanket waving as a form of modulation used in smoke signal transmission (the

carrier being a steady stream of smoke).

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NoteGeneric class for demodulators.

A demodulator is a device which extracts arbitrarily varying information from a signal formed by varyinga characteristic of a repetitious electrical or electromagnetic wave of less than infrared frequency.

Microwave PrinciplesMegastar 155 Microwave RadioModulation 3Demodulation

Demodulation definition - The conversion of a modulated carrier wave into a current equivalent to theoriginal signal. Also called detection .

The act or process by which an output wave or signal is obtained having the characteristics of the originalmodulating wave or signal; the reverse of modulation

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Microwave PrinciplesDigital Microwave CommunicationModulation 4

Amplitude Shift Keying (ASK)Uses the digital baseband signal to change the carrier amplitude (A), carrier frequency (f c) andcarrier phase ( ) remain unchanged.

Frequency Shift Keying (FSK)Uses the digital baseband signal to change the f c, A and remain unchanged.

Phase Shift Keying (PSK)Uses the digital baseband signal to change the , f c and A remain unchanged.

Quadrature Amplitude Modulation (QAM)Uses the digital baseband signal to change the and A, f c remains unchanged

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The baseband signal is the un-modulated digital signal. The baseband IF can not be directly transmittedover microwave radio channels and must be heterodyned (mixed) the RF (7GHz or 8GHz) for microwave medium for communication.

Digital Base band Intermediate Frequency SignalBaseband

ServiceSignal

Transmitted


PSK and QAM are mostfrequently used in digitalmicrowave transmission

Signal R

ate

Modulation

TransmittedServiceSignal

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Voltage

Digital

Voltage

Voltage

Digital

Digital

0

0

0

Time

Time

Time

Phase Shift

Phase Shift Amplitude Modulation

Phase Shift Modulation

Un-Modulated (reference)Modulated ( Phase Shifted)

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Microwave PrinciplesDigital Microwave CommunicationModulation 7Quadrature Amplitude Modulation - 1

QAM-16

QAM-64

QAM-128

The higher the modulation stagesmaller the channel/bandwidth getsmore sensitive to interferenceSynchronous Digital Hierarchy

DMRS 155/Mbits/secTransmission

Channel128 QAM

Bandwidth

< 26 MHz

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Quadrature Amplitude ModulationConstellation DiagramExamples-Quadrature AmplitudeModulation is actually indisplayed in Polar Coordinaterepresentation The I and Qcomponent is converted to atwo dimensional planerepresentation.

Where I is in the X PlaneQ is in the Y Plane

The Diagram is a working model

demonstrating I and Q


QAM -12864 bits per Quaadrant

QAM 6416 bits per Quadrant

QAM-164 bit per quadrant

QPSK

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QAM is a family of encoding schemes that are widely used for encoding multiple bits of 1 and 0 per symbol that combine Amplitude and Phase Modulation, with frequency remaining constant.

16, 64, 128 QAM are a common forms using 8 bit, 32 bit , and 64 bit phase shifts and 2 changingamplitude levels, respectively.

For 16 bit QAM - Since there are 16 possible symbols, each symbol encodes 4 bits

For 64 bit QAM - Since there are 64 possible symbols each encoded symbol represents 8 bits

For 128 bit QAM - Since there are 128 possible symbols each encoded symbol represents 32 bits(The scheme most commonly used)

QAM and related techniques are commonly used for precise transmission and reception of digitaldata streams. (More commonly used for modems with a data rate of up to about 28 kilobits/second. )


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Voltage

Digital

VoltageDigital

0

0

Time

Time

Time

Phase Shift Modulation

Phase Shift

Amplitude Modulation Phase Shift

Un-Modulated (reference)Modulated ( Phase Shifted)

0

Voltage

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QAM is a combination of amplitude modulation, changing the amplitude or voltage of a sine wave toconvey information together with phase modulation.

Explaining QAM modulation

Two modulating carrier waves are derived by special pre-processing from the information bit stream. Replica carrier waves are generated; one carrier wave is a direct replica sin (I) and the other carrier wave is delayed by a quarter of acycle (90) cos (Q). Each of the two carrier waves are derived by modulating the signals to the amplitude of the twocarrier waves I and Q respectively.

The resultant two modulated signals are algebraically summed together, the result is an I and Q having a constantunchanging frequency while the amplitude and phase will vary to convey the information.

At the detector or decoder the original information bit stream can be reconstructed.

QAM conveys a higher information bit rate.

This method of modulation has the advantage of reducing or eliminating inter-modulation interferencecaused by a continuous carrier wave near the modulation sidebands.

This carrier wave for all intents and purposes is a 'Double Sideband Signal' (DSB) with or without acarrier (reduced). (Only one side band is used for processing information).


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171.072 MB/s

1.552 MB/s STM-1 155.2 MB/s

RFCOH SOH PAYLOAD

MCLM11.84Mb/s

DMY64Kb/s

XPIC16Kb/s

ATPC64Kb/s

WS2.24Kb/s

RSC864Kb/s

INI144Kb/s

ID32Kb/s

FA288Kb/s

RFCOH: Radio Frame Complementary Over HeadMLCM: Multi-Level Coded ModulationDMY: DummyXPIC: cross polarization interference counteract

ATPC: Automatic Transmitter Power ControlWS: Wayside ServicesRSC: Radio Service ChannelINI: Switch Instruction

ID: Identifier FA: Frame Alignment

Microwave PrinciplesMicrowave CommunicationDigital Frame Structure 1

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Multiframe 3564 bits

6 bits FS6 bits

Basic Frame 11776 bits (148 words)

FS6 bits

Basic Frame 21776 bits (148 words)

I STM1 information bit (OCR information bit)C1 correction coding supervision bit of first level,C2 correction coding supervision bit of second levelFS frame synchronization bita other complementary overhead bits

b other complementary overhead bits

Microwave PrinciplesMicrowave CommunicationDigital Frame Structure 2

I I I I I I I I I I I I I I I I I I I I I I I I





I I I I I I I I b I I C2 I I I I I a I I b I I C2

I I C1 I I C1 I I C1 I I C1 I I C1 I I C1 I I C1 I C1 I

12 bits (1 st Word) 12 bits (148 th Word)

RFCOH is multiplexed into the STM-1 data and a block multi-frame is formed. Each multi-frame has six rows and each row has 3564 bits. Onemulti-frame is composed of two basic frames. Each basic frame has 1776 bits. The remaining 12 bits are used for frame alignment

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What is microwave?

What is digital microwave communication?

What are the frequently used digital microwave frequency bands?

What concepts are involved in microwave frequency setting?

What are the most frequently used modulation schemes?

Microwave PrinciplesQuestions

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Microwave PrinciplesContentsModule 2

Digital Microwave Communication Equipment

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Microwave PrinciplesMicrowave Equipment Category

System Digital Microwave

PDH SDH

Analog Microwave

MUX/DEMUXMode

Capacity

Structure

Small and Medium Capacity

2 16 E1 34 Mbits/sec

Large CapacitySTM-0, STM-1, 2xSTM-1

Discontinued

Trunk

Split Mount Radio

All Outdoor Radio

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Microwave PrinciplesMicrowave Antenna 1

0.3m - 1 foot0.6m - 2 feet1.2m - 4 feet1.8m - 6 feet2.0m2.4m - 8 feet3.0m - 10 fee3.7m - 12 feet

Antennas are used to send and receive microwave signals, a Parabolic antenna is the common type of the

microwave antenna.

Microwave antenna diameters includes

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Microwave Principles Antenna Adjustment 3

Main lobe

Side View

Top View

Main lobe

Main lobeHalf-power angle

Half-power angle

Tail lobe

Tail lobe

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During antenna adjustment, the two wrongadjustment cases are shown here. One antenna isaligned to another antenna through the sidelobe.

As a result, the RSSI can not meet therequirements.

Wrong Wrong Correct

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During antenna adjustment,Use a spectrum analyzer to observe the RSSI at the

receiving end, perform fine adjustments on theantenna and observe the RF is signal is a maximumas observed on the spectrum analyzer, asdemonstrated in the illustration to the right.

Change the antenna direction vertically or horizontally,use a multimeter to observe voltage, the peak point of the voltage, perform fine adjustments on the antennato peak the voltage point, (usually the voltage peakwill be displayed as shown in the lower right corner) .

When antennas are poorly aligned a small or no RFsignal will be displayed, or a small voltage may bedetected in one direction. In this case, perform coarseadjustment on the antennas at both ends, so that theantennas are roughly aligned.

The antennas at both ends that are well aligned face alittle bit upward. Though 1 2 dB is lost, reflectioninterference will be avoided

AGC Voltagedetection point

Side LobePosition

Main lobeposition

Angle

RF Display

Microwave Principles Antenna Adjustment 5

AGC

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Microwave PrinciplesTrunk Microwave Equipment

Low costLarge transmission capacityMore stable performanceapplicable to long-haul and trunktransmission

antenna system is outdoors

IF

The RF processing isperformed in the RadioFrequency Unit(RFU)

signal processing unit (SPU) - known as baseband module

The Exciter is where and RFcreated and, where the RFand IF signals areheterodyned (mixed)

Antenna Coupling Unit (ACU)

SDH MICROWAVE RADIOHarris Megastar 155Digital Microwave Transmission

Parabolic antenna

RF

Modulator MUX

Demodulator DEMUX

R a d i oF r e

q u en

c y Uni t

( RF

U )

Option(OC3)optical interface

Multi-Mode

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The MegaStar 155 Microwave Radio is a high capacity point-to-point digital microwave radio available at 7/8 GHz.

Is a compact, single platform.

Can be upgraded from 1 to 7 high capacity channels (155 MBit/s each).

Features include 10BASE-T transport for OEM equipment connection to SNMP management, support for OpenNetwork Management through an SNMP proxy, convenient provisioning with remote software download,

Remote and Localinventorying

Plug and play module replacement

Easy maintenance with local IF loopback with built in test signal for BER measurement.

consists of primary and redundant circuit cards and modules

Microwave PrinciplesMegastar 155 Microwave Radio

Standard FeaturesProvides a high level of readiness

Receiver fully digital adaptive time domain equalization (ATDE)Receiver fully digital adaptive slope equalizationForward Error Correction (FEC)Anticipatory errorless receiver switchingReverse Path ProtectionTransmitter Automatic Transmit Power Control (ATPC)

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Standard FeaturesProvides a high level of readiness

Receiver fully digital adaptive time domain equalization (ATDE)Receiver fully digital adaptive s lope equalizationForward Error Correction (FEC)

Anticipatory errorless receiver switchingReverse Path ProtectionTransmitter Automatic Transmit Power Control (ATPC)

Offers self-aligning operation

Inventory Reporting(SCAN) System Control and Alarm Network - Remote MonitoringFarscan Local Diagnostics using portable computer (Laptop)

Replace Me/Loss of Signal LEDAutomatic calibration of replacement circuit packsLocal/Remote firmware replacement

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3A. Signal Processor (SPU) 1

1A. Antenna Coupling Unit (ACU) 1

Can consist of 2 Microwave Radio Systems in one shelf andeach Systems consist of 3 subsystems each

2B. Radio Frequency Unit (rfu) 22A. Radio Frequency Unit RFU) 1

1B. Antenna Coupling Unit (ACU) 2

3B. Signal Processor (SPU) 2

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Processes Digital Data

Sends Digital Data to RF combiner for mixing digital data with the 70 MHz Intermediate Frequency (IF)commonly called the carrier frequency.

Frequency domain representation of output

Microwave PrinciplesMegastar 155 Microwave RadioIntermediate Frequency

70 MHz70 MHz

Single Side Band Carrier (IF) frequency

70 MHz 70 MHz

Double Side Band Carrier (IF) frequency

Frequency domain representation of input

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The IF mixer extracts 70 MHz carrier frequency from the receiver RF

Processes the 70 MHz carrier frequency to the demodulator input a part of the base band(Megastar 155 SPU)

Microwave PrinciplesMegastar 155 Microwave RadioIntermediate Frequency

Undesired Signals Undesired Signals

70 MHz

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Receiver ALow Noise Converter

PLS

IF Amplifier

ACU

Couples RF signal from Power Amplifier assembly to antenna

Receiver BLow Noise Converter

PLS

IF Amplifier

Transmitter APower Amplifier A

RF Switch & Filter Assembly A

PLS A

Transmitter BPower Amplifier B

RF Switch & Filter Assembly B

PLS B

RFU

B A

Single Power Amplifier ConfigurationMicrowave Principles

Megastar 155 Microwave Radio

ACU

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ACU


PLS

IF Amplifier


ACU



PLS

IF Amplifier


Transmitter A

Power Amplifier A


PLS A



PLS B

RFU

B A

Parallel Power Amplifier Configuration


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ACU


PLS

IF Amplifier

ACU



PLS

IF Amplifier

Transmitter APower Amplifier A


PLS A



PLS B

RFU

B AMicrowave PrinciplesMegastar 155 Microwave Radio

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Slot 9Slot 12Slot 6

Slot 15Slot 5Slot 4

Slot 17Slot 16 Slot 18

Slot 13Slot 8 Slot 10

Microwave PrinciplesMegastar 155 Microwave RadioSignal Processor Unit (SPU)

Slot 1Slot 2

Slot 3

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Slot 9 Slot 12

Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal FlowTributary Interface Card

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Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal FlowModulator Card

Slot 8 Slot 16

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Selects the active Tributary Interface Transmitter

Modulates 70 MHz Intermediate Frequency (IF) carrier

128 Quadrature Amplitude Modulation (QAM)

processes IF signal to transmitter (a part of the RFU assembly).

Houses digital to analog converter.

Two Fault Indicators and one connector

Fault LED indicates a fault or signal loss in the Modulator Unit

Active LED indicates Modulator is Active

IF carrier out SMA connector Tx 70 MHz IF carrier out to the RFU

Controlled and monitored through SPU controller.

Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal FlowModulator Card

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RF Switch Assembly

Heterodynes the 70 MHz IF carrier frommodulator and signal from LO together toproduce double sideband signal.

Passes upper or lower side band signaland RF carrier signal to RF switchassembly. Upper or lower sideband signal

feeds through sideband select f ilter. (Thisfilter passes only desired RF signal topower amplifier.)

RF Out

IF in

Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal FlowRadio Frequency (RF) Switch

RF In

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Part of the Power Amplifier assembly located in the power amplifier

Controls the status and communications task for the RFU through the controller located in the SPU.

Provides monitoring of the RFU assembly through the controller assembly in theSPU

Supplies DC power for all associated RFU modules.

Transmitter Assembly

Receiver Assembly

Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal FlowRadio Frequency Unit Controller

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Filters and routes RF signals from transmitter power amplifier to antenna port.

Single Power Amplifier Antenna Coupler Unit

Antenna Coupler Unit

Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal Flow


Dual Power Amplifier

Two Types of Transmitter

Power output configurations

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Provides DC Power to transmitter, receiver, and RFUcontroller

Consists of power amplifier subassembly, RF controller and bias card.

Provides RF amplification of the IF signal.

ATPC - Automatic Transmitter Power Control.

RF Out

RF In

Power Switch

Fault LED

Active LED

Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal FlowSingle Power Amplifier Configuration

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Provides DC Power to transmitter, receiver, and RFUcontroller

Consists of power amplifier subassembly, RFcontroller and bias card.

Provides RF amplification of the IF signal.

ATPC - Automatic

RF Out

RFIn

Power Switch

Fault LED

Active LED

Transmitter

Power ControlMicrowave PrinciplesMegastar 155 Microwave RadioTransmitter Signal FlowDual Power Amplifier Configuration

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Single Power Amplifier Antenna Coupling Unit


Dual Power Amplifier Antenna Coupling Unit (ACU)


If needed power is boosted from the second power amplifier in the configuration

Microwave PrinciplesMegastar 155 Microwave RadioTransmitter Signal Flow


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Antenna SystemSpace Diversity (only for receiver)

Waveguide

The antenna transfers the Radio Frequencyfrom the transmitter module and receiver module.


Antenna Signal Flow

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Couples RF signal from antenna to low noise converter

Microwave PrinciplesMegastar 155 Microwave RadioReceive Signal Flow

Antenna Coupling Unit

Low Noise Converter

Phase Lock Source

IF filter/amplifier

Receiver Assembly

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Low Noise Converter (LNC)

Amplifies received signal from ACU

Mixes received signal with local oscillator frequency

The LNC processes the data to the IF amplifier wherethe 70 MHz IF carrier is separated from the RF

Microwave PrinciplesMegastar 155 Microwave RadioReceive Signal FlowRadio Frequency Unit

RF in

Fault Indicator

Low Noise Converter

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provides constant output /selectivity level approximately 7db lower than receiver power

Improves delay and equalization with AGC current.

IF Amplifier Fault

Microwave PrinciplesMegastar 155 Microwave RadioReceive Signal FlowIntermediate Frequency (IF) Amplifier

IF out

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Slope equalizes received 70 MHz IF carrier from RFU.Demodulates IF carrier information into digitized symbols (analog to digital converter).

Recovers clock from received signal.

Controlled and monitored by SPU.

Notegeneric class for demodulators .

A demodulator is a device which extracts arbitrarily varying information from a signal formed by varying a characteristic of

a repetitious electrical or electromagnetic wave of less than infrared frequency. Classification herein is broadly by thetype of modulation exhibited by the input signal.

Microwave PrinciplesMegastar 155 Microwave RadioReceive Signal FlowDemodulator

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Slot 6 Slot 15

Microwave PrinciplesMegastar 155 Microwave RadioReceive Signal FlowDecoder

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Decodes the demodulated digital data QAM In-Phase and Quadrature signals

Controls the demodulator card Voltage Controlled Oscillator (VCO)

Provides error correction based on Forward Error Correction (FEC) technology

Controlled and monitored by SPU controller

Microwave PrinciplesMegastar 155 Microwave RadioReceive Signal FlowDecoder

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Provides physical connection multi-mode fiber OC-3 connectivity.

Recovers clock pulse of the incoming signal.

Switches receivers errorless using DADE Differential Absolute Delay Equalization circuitry

The SPU one unit in a non-protected and two units in a protected configuration

Three fault indicatorsFault LED indicates a fault

Transmitter (Tx) LED indicates active transmitter

Receive (Rx) LED indicates active receiver

The tributary Interface Unit is controlled and monitored via the SPU Controller

NOTE

The Transmit and Receive indicators do not have to be on the same Tributary Indicator Card

Microwave PrinciplesMegastar 155 Microwave RadioReceive Signal FlowTributary Interface Card

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Slot 4 Slot 17

Microwave PrinciplesMegastar 155 Microwave RadioDC to DC converter

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Requires + 24 volts DC to + 48 volts DC from proper power source.Unit provides +12 VDC, -12 VDC and +5.2 VDC (regulated voltage) for SPU circuit card operation.

Standard power source

- 56 VDC to - 21 VDC or + 56 VDC to +21 VDC (with respect to ground).

USFK Digital Microwave Radio uses -48 Volts DC

Microwave PrinciplesMegastar 155 Microwave RadioDC to DC converter

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Slot 10

Microwave PrinciplesMegastar 155 Microwave RadioController Card

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Monitors alarms and status of SPU shelf Provides control for transmitter/receiver switching

Stores and runs Megastar processor information

With loss of SPU Controller card

Process 90% of incoming traffic

Loses automatic switching capabilities

One Controller card per system (no redundancy)

Microwave PrinciplesMegastar 155 Microwave RadioController Card

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Farscan /NETBOSS (formerly Star Scan) diagnostic utility programTNOSC (Camp Walker) uses NETBOSS at monitor console for monitoring and diagnostic testing

MST uses Farscan loaded on laptop for local diagnostic testing

64 KBPS allocated for overhead as F1 channel used for monitoring Megastar 155 Microwave Radiosystem through out South Korea

Security levels 0 through 7 determine type and number of manual commands available at each site -level determined by Master Farscan Administrator

Microwave PrinciplesMegastar 155 Microwave RadioSystem Maintenance

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Module fault indicator guideBlinking red - loss of signal prior to output signalSteady red - probable fault at observed indicator signalGreen - Signal is good at module


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Monitored and supervised via Farscan (Local Diagnostics) and NETBOSS (Remote Diagnostic) software.Remote monitoring by TNOSC at Camp Walker.Trouble isolation

When necessary performed by MST through laptop computer connection.

Megastar Microwave radio automatically switches after fault detection the following sub systems:Transmitter Receiver

No calibration or testing required after replacement of defective parts or defective units (modules).


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Microwave PrinciplesMegastar 155 Microwave RadioSimplified Overall Block Diagram (final)

Antenna

ATM36170

ATM36170

Signal Processor Unit

TributaryInterface

Demodulator/Decoder

Antenna

Modulator

O&MInterface

O&M Conversion

SupervisionControl

DC to DCConversion

Power Interface

Power Interface

DC to DCConversion

O&M Conversion

SupervisionControlO&MInterface

ANTENNA COUPLINGUNIT (ACU)

RF InRF Out

RECEIVER A/B

Transmitter A/B

RADIO FREQUENCY UNIT(RFU)

70 MHz IF

RF Out

RF InRF Out

RECEIVER A/B

Transmitter A/B

RADIO FREQUENCY UNIT(RFU)

Signal Processor Unit Demodulator/

Decoder

TributaryInterface

ANTENNA COUPLINGUNIT (ACU)

Transmit frequency+

70 Mhz

70 MHz IF

Receive Frequency+

70 Mhz

RF OutRF In

Transmit Frequency+

70 Mhz

Receive frequency+

70 Mhz

W a v e

G u i

d e

70 MHz IF70 MHz IF

Modulator

W a v e

G u i

d e

RF In

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Microwave PrinciplesMegastar 155 Microwave RadioOverall Block Diagram

TributaryInterface Unit

Supervision Channel

LineUnit

DC to DC conversion

O&M Interface

Power Interface

MicrowaveFrameMultiplexing

Service Channel

Microwave

FrameDe-Multiplexing

Modulation

Rx IF

Tx IF

From/To Antenna

Cable In

ter f ace

Service Channel

De-Modulation

Cr oss Connects

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What types are microwave equipment classified into?

What are the key specifications of the microwave radio signal processing unit (sometimes called the baseband module)?

What are the key specifications of the microwave radio transmitter and receiver ?

What are the key specifications of the antenna coupling unit?

Can you describe the entire signal flow of a microwave transmission?

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Microwave PrinciplesSummary

Classification of digital modules in microwave equipment

Components of microwave equipment and their functions

Antenna installation and key specifications of antennas

Functional modules of basic microwave radio

Signal flow of microwave transmission

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Microwave PrinciplesContentsModule 3

Digital Microwave Networking and Application

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Relay Station

Terminal Station

Terminal Station

Terminal Station

Pivotal Station

ADD-DROPRelay Station

Microwave PrinciplesRelay Stations 1Types of Digital Microwave

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Microwave PrinciplesRelay Station 2Types

Terminal Station

Terminal Station

Terminal Station

Relay Station

Pivotal Station

ADD/DROPRelay Station

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Microwave PrinciplesRelay Stations 3Types

Relay Station

Passive

Active

RF Repeater

RegenerativeRepeater

IF Repeater

Back to back AntennaPlane

Reflector

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Active - bi-directional - without frequency shift.

Directly amplifies the signal over radio frequency.

Microwave PrinciplesRelay Station 4

Active Relay Station

The regenerator relay station is used to extend the transmission distance of microwave communicationsystems, or to deflect the transmission direction of the signal to avoid obstructions and ensure the signalquality is not degraded. After complete generation and amplification, the received signal is forwarded

Regenerator Relay Station

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Microwave PrinciplesRelay Station 5

Active Relay Station

PassiveStation

Special Meters are necessary to adjust antennas, (is time consuming)

Near end is less than 5 km away

Parabolic reflector passive relay stationComposed of two parabolic antennas connected by a soft waveguide back to back

Often uses large-diameter antennas

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Passive Relay Station

Microwave PrinciplesRelay Station 6Plane Reflector Passive Relay Station

Metal board having smooth surface, proper effective area, proper angle and distancewith two communication points

Two Communication PortsTwo Communication Points

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Passive Relay Station - Plane Reflector Passive Relay Station - Parabolic Antenna

Microwave PrinciplesRelay Station 7Passive Relay (Photos)

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Microwave Principles Application of Digital Microwave

BTS BackhaulTransmission

Complementarynetworks to opticalnetworks, (accessnetworks from the

last 1km)Special

transmissionConditions

Rivers, lakes,

islands, etcMicrowave

Applications

Redundancy backup of important links

VIP Customer Access

EmergencyCommunications

conventions,activities, danger

elimination, disaster relief, etc.

BTS BackhaulTransmission

Complementarynetworks to opticalnetworks, (accessnetworks from the

last 1km)

Special transmissionConditions Rivers,lakes, islands, etc

Microwave Applications

VIP Customer Access

Redundancy backup of important links

EmergencyCommunications

conventions,activities, danger

elimination, disaster

relief, etc

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Microwave Principles 93


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What networking modes are frequently used for digital microwave?

What are the types of digital microwave stations?

What are the types of relay stations?

What is the major application of digital microwave?


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Microwave PrinciplesModule 4

Microwave Propagation and Anti-fading Technologies

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4.1 Factors Affecting Electric Wave Propagation

4.2 Various Fading in Microwave Propagation

4.3 Anti-fading Technologies for Digital Microwave

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RT

P

Microwave PrinciplesParameters in Microwave PropagationParameters 1

Fresnel Zone - Fresnel Zone Radius

The elliptical region encircled by the trail of P is called Fresnel zone

Fresnel zone radius: Vertical distance from P to the TR line is the first Fresnel zone radius represented by F n (n=1).

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Microwave PrinciplesParameters in Microwave PropagationParameters 2Fresnel Zone - 2

F r e s n e l

Z o n e

Total Distance

A n t e n n a

H e i g h

t

E a r

t h C u r v a

t u r e

O b s t r u c

t i o n s

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Microwave PrinciplesMicrowave PropagationParameters 2Fresnel Zone - 3

Along the microwave propagation trail, obstruction from buildings, trees, and mountain peaks issometimes inevitable.

If the height of the obstacle enters the first Fresnel zone, additional loss might be caused.

The received level is decreased and the transmission quality is affected. Clearance is used to avoid thecase described previously

The vertical distance from the obstacle to AB line segment is called the clearance of the obstacle on thetrail. For convenience, the vertical distance h c from the obstacle to the ground surface is used to representthe clearance.

In practice, the error is not big because the line segment AB is approximately parallel to the groundsurface. If the first Fresnel zone radius of the obstacle is F 1, then h c / F1 is the relative clearance

h1

h0

A B

hc h s

d1 d2d

h0

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Mi P i i l

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Smooth ground or water surface can reflect part of the signal energy transmitted by the antenna to thereceiving antenna and cause interference to the main wave(direct wave).

The vector sum of the reflected wave and main wave increases or decreases the composite wave.

As a result, the transmission becomes unstable, therefore in microwave link design, avoid reflected wavesas much as possible

If reflection is inevitable, make use of the terrain ups and downs to block the reflected waves

Microwave PrinciplesWave PropagationFactors Affecting - ElectricTerrain

0

Micro a e Principles

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Passive Relay Station

Microwave PrinciplesRadio Frequency Relay StationPlane Reflector Passive Relay Station

Metal board having smooth surface, proper effective area, proper angle and distancewith two communication points

Two Communication PortsTwo Communication Points

1

Microwave Principles

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Different reflection conditions of different terrains have different effects on electric wave propagation.Terrains are classified into the following four types:

Type A mountains (or cities with dense buildings)Type B hills (gently wavy ground surface)Type C plains (flat Land)Type D large-area water surface

The reflection coefficient of mountains is the smallest, and thus the mountain terrain is most suitable for microwave transmission. The hill terrain is less suitable. When designing circuits, try to avoid smooth planesuch as water surface

Microwave PrinciplesWave PropagationFactors Affecting ElectricTerrain 2

2


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The troposphere indicates the low altitude atmosphere within 10 km from the ground, microwave antennaswill not be higher than the troposphere, so the electric wave propagation in aerosphere can be narrowedthat in the troposphere. Main effects of the troposphere on electric wave propagation are listed below:

Absorption caused by gas resonance. This type of absorption can affect microwave radiation at 12 GHz or higher.

Absorption and scattering caused by rain, fog, and snow. This type of absorption can affect the microwave radiation at 10GHz or higher.

Refraction, absorption, reflection and scattering caused by homogeneity of atmosphere. Refraction is the most significant

impact to microwave radiation and propagation

Microwave PrinciplesWave PropagationFactors Affecting Electric

Atmosphere

3


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4.2 Various FadingTypes in Microwave Propagation

Microwave PrinciplesMicrowave PropagationFading

4


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Microwave PrinciplesMicrowave Propagation

Anti-Fading Technologies 8Frequency Diversity

Signals at different frequencies have different fading characteristics Accordingly, two or more microwavefrequencies with certain frequency spacing to transmit and receive the same information is then selected or

composed to reduce the influence of fading. This work mode is called frequency diversity.

Advantage The effect is obvious. Only one antenna is required.Disadvantage The utilization ratio of frequency bands is low

Apart from the anti-fading technologies introduced previously, a frequently used tips:Make use of some terrain and ground objects to block reflected waves

f1

f2

5


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Anti-Fading Technologies - 9Space Diversity

Signals have different multipath effect over different paths and thus have different fading characteristics. Accordingly, two or more suites of antennas a to different altitude levels to receive the signals at the samefrequency which are composed or selected. This work mode is called space diversity. If there are in pairs

of antennas, it is called n-fold diversity. Advantage The frequency resources are saved.Disadvantage The equipment is complicated, as two or more suites of antennas are required.

Antenna distance, the distance between the diversity antennas is 100 to 200 times the wavelength infrequently used frequency bands

Apart from the anti-fading technologies introduced previously, a frequently used tips:high and low antennas

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Importance parameters affecting microwave propagation.

Various factors affecting microwave propagation.

Various fading types in the microwave propagation (free space propagation fading, atmosphericabsorption fading, rain or fog scattering fading, K type fading, multipath fading, duct type fading, andscintillation type fading).

Anti-fading technologies.

Anti-fading measures adopted on the equipment: adaptive equalization, and ATPC.

Anti-fading measures adopted in the system.

Microwave PrinciplesMicrowave PropagationPropagation and Anti-Fading TechnologiesSummary

8


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What networking modes are frequently used for digital microwave?

What are the types of digital microwave stations?

What are the types of relay stations?

What is the major application of digital microwave?

Questions9


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4.2 Various Fading in Microwave Propagation


1


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2


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RT

P

pParameters in Microwave PropagationFresnel Zone - 1Fresnel Zone - Fresnel Zone Radius

The elliptical region encircled by the trail of P is called Fresnel zone

Fresnel zone radius: Vertical distance from P to the TR line is the first Fresnel zone radius represented by F n (n=1).

3

Microwave PrinciplesParameters in Microwave Propagation

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p gFresnel Zone - 2

F r e s n e l

Z o n e

Total Distance

A n t e n n a

H e i g h

t

E a r

t h C u r v a

t u r e

O b s t r u c

t i o n s


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pParameters in Microwave Propagation Fresnel Zone - 3

Along the microwave propagation trail, obstruction from buildings, trees, and mountain peaks issometimes inevitable.

If the height of the obstacle enters the first Fresnel zone, additional loss might be caused.

The received level is decreased and the transmission quality is affected. Clearance is used to avoid thecase described previously

The vertical distance from the obstacle to AB line segment is called the clearance of the obstacle on thetrail. For convenience, the vertical distance h c from the obstacle to the ground surface is used to representthe clearance.

In practice, the error is not big because the line segment AB is approximately parallel to the groundsurface. If the first Fresnel zone radius of the obstacle is F 1, then h c / F1 is the relative clearance

h1

h0

AA

B

hc h s

d1 d2d

h0

Microwave PrinciplesF Aff i El i W P i

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Smooth ground or water surface can reflect part of the signal energy transmitted by the antenna to thereceiving antenna and cause interference to the main wave(direct wave).

The vector sum of the reflected wave and main wave increases or decreases the composite wave.

As a result, the transmission becomes unstable, therefore in microwave link design, avoid reflected wavesas much as possible

If reflection is inevitable, make use of the terrain ups and downs to block the reflected waves

Factors Affecting Electric Wave PropagationTerrain


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Microwave PropagationFading

Fading: Random variation of the received level. Thevariation is irregular and the reasons for this arevarious.

Fading Mechanics Fading Time Received LevelInfluence of

Fading on Signal

Pr opoga

tion Fading

Fr ee Space

Absor pt

ioN

Fading

Rain

Fading

F

ading

Scintillation

K Typ

e Fading

Duct T

ype Fading

Fast Fading

Slow

Fading

Up

Fading

Down Fading

Flat

Fading

Fading

Selective Fr equency


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Microwave PropagationFading

Free space loss: A = 92.4 + 20 log d + 20 log f d - diameter f - frequency If d or f is doubled, the loss will increase by 6 dB

P T x = Transmit power P R x = Receive power G = Antenna Gain

AO = Free Space LossM = Pading Margin

M

G

G

G Tx G Rx d

f

Power

Level

P Rx

Receiver Threshold

Antenna Antenna

Distance

P Tx


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Microwave Propagation Absorption Fading

Molecules of all substances are composed of charged particles. Particles have their own electromagnetic resonant frequencies. When microwave frequencies of substances are close to resonance frequencies - resonance absorption occurs to themicrowave.

Statistics shows absorption to microwave frequencies lower than 12GHz is smaller than 0.1 dB/km.

Compared with free space loss, the absorption loss can be ignored.10 db

1 db

0.01 db

60 GHz 23 GHz 12 GHz 7.5 GHz 1.0 GHz

.1 db


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For frequencies lower than 10 GHz, rain loss can be ignored minimal db may be added to a relay section.

For frequencies higher than 10 GHz, repeater spacing is mainly affected by rain loss. For example 13 GHzfrequency or higher 100mm/h rainfall will causes a loss of 5 dB/km. Hence for the 13 GHz and 15 GHzfrequencies the maximum relay distance is about 10 km. For the 20 GHz frequency and higher the relaydistance is limited to one or two kilometers due to rain loss.

High microwave radio frequency bands can be used for user-level transmission. The higher the frequency bandis, the more severe the rain fading is.

Microwave PropagationRain Fading


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Atmosphere refraction

As a result of atmosphere refraction, the microwave propagation trail is bent. It is considered that theelectromagnetic wave is propagated along a straight line above the earth with an equivalent earth radiusof , = KR (R: actual earth radius.)

The average measured K value is about 4/3. However, the K value of a specific section is related to themeteorological phenomena of the section. The K value may change within a comparatively large range. This canaffect line-of-sight propagation.

R e

R e Rx

R e

Microwave PropagationK Type Fading - 1


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Atmosphere refraction

As a result of atmosphere refraction, the microwave propagation trail is bent. It is considered that theelectromagnetic wave is propagated along a straight line above the earth with an equivalent earth radiusof , = KR (R: actual earth radius.)

The average measured K value is about 4/3. However, the K value of a specific section is related to themeteorological phenomena of the section. The K value may change within a comparatively large range. This canaffect line-of-sight propagation.

Microwave PropagationK Type Fading - 1

R e

R e

Rx

R e

Microwave PrinciplesMi P ti

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k =

43

1

Ground surface Actual Earth Radius (r)

1

43

k =

Equivalent Earth Radius (r) 23

23

In temperate zones the refraction when the K value is 4/3 is referred as a standard atmosphere, and R e whichis 4/3 is the standard.

Microwave PropagationK Type Fading - 2Equivalent Earth Radius

43

1

23

Microwave PrinciplesMicrowave PropagationK T F di 2

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k > 1: Positive refraction

k = 1: No refraction

k < 1: Negative refraction

K Type Fading - 2

Microwave PrinciplesMicrowave PropagationMultipath Fading 1

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Multipath fading is caused by multipath propagation of refracted waves, reflected waves, scattered waves,

and multiple electric waves which are received at the receiving end. The composition of these electricwaves will result in severe interference fading.

Down fading - the composite wave level is lower than the free space received level.Up fading - the composite wave level is higher than the free space received level.

Reasons for multipath fading are reflections due to non-uniform atmosphere, water surface and smoothground surface.

Non-uniform atmosphere

Water surface

Smooth ground surface .

Ground Surface

Multipath Fading - 1

Antenna Antenna

Ground Wave


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Microwave PrinciplesMi P g ti

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Normal

FlatSelectivity Fading

Frequency (MHz)

Microwave PropagationMulti Path - Frequency Selective Fading

Multipath fading frequency selective fadingType of interference fading caused by multipath transmission. Multipath fading is caused by mutual interference between the directwave and reflected wave (or diffracted wave on some conditions) with different phases

Grows more severe when waves pass over water surfaces or smooth ground surfaces. When designing the route, try to avoidsmooth water and ground surface. When these terrains are inevitable use the high and low antenna technologies to bring thereflection point closer to one to reduce the impact of the reflected wave.

Use the high and low antennas and space diversity technologies, or the antennas that pointed away from reflectedwaves to overcome multipath fading.


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UpFading

SignalInterruption

ReceivedLevel in Free

Space

Threshold Level(-30 db)

1h

Microwave PropagationMulti Path - Flat Fading

Multi Path - Flat Fading


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Duct FadingDue to the effects of meteorological conditions such as

ground cooling in the night,burnt warm by the sun in the morning,smooth sea surface,anticyclone a non-uniform structure is formed in atmosphere.

This phenomenon is called atmospheric ducting.If microwave beams pass through the atmospheric duct while the receiving point is outside the ductlayer, the field strength at the receiving point is from not only the direct wave and the reflected

ground wave, but also the reflected wave from the edge of the duct layer. As a result, severeinterference fading occurs and causes interruption to the communications

Scintillation FadingScintillation fading is a type of fast fading which lasts a short time. The level changes little and themain wave is barely affected. Scintillation fading will not cause communications interruption.

When the dielectric constant of local atmosphere is different from the ambient atmosphere due to theparticle clusters formed under different

pressure,temperaturehumidity

NOTEScattering occurs to the electric wave. This is called scintillation fading. The amplitude and phase of different scattered waves vary with the atmosphere. As a result, the composite field strength at thereceiving point changes randomly.

Microwave PropagationDuct and Scintillation Fading

Microwave PrinciplesMi P ti

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Microwave PropagationScintillation and Duct Fading

Duct Fading

Scintillation Fading


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Microwave PropagationSummary

The higher the frequency is and the longer the hop distance is, the more severe the fading is.

Fading is more severe at night than in the day, in summer than in winter. In the day, sunshine is goodfor air convection. In summer weather changes frequently.

In sunny days without wind, atmosphere is non-uniform and atmosphere subdivision easily formsand hardly clears. Multipath transmission often occurs in such conditions.

Fading is more severe along water routes than land routes, caused by the reflection coefficient of water surface and the atmospheric refraction coefficient above water surface.

Fading is more severe along a plain (flat land) route than a mountain route, the atmospheresubdivision often occurs over the plain and the ground reflection factor of the plain is bigger.

Weather - rain and fog influences microwave frequencies.


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Microwave Propagation Anti-Fading Technologies


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The frequency domain equalization only equalizes the amplitude frequency response characteristics of thesignal not the phase frequency spectrum characteristics .

Frequency domain equalization

Microwave Propagation Anti-Fading Technologies 2

SignalFrequencySpectrum

FrequencySpectrum After

EqualizationMultipath

Fading

SlopeEqualization


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T T

Before

After

-2Ts -Ts -2Ts

Ts Ts -Ts

Cn Co

Microwave Propagation Anti-Fading Technologies 3

T

Frequency domain equalizationTime domain equalization directly counteracts the inter-symbol interference


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Automatic transmit power control (ATPC) under normal propagation conditions, the output power of the transmitter is always at a lower level, (for example 10 dB to 15 dB lower than the normal level.

When propagation fading occurs and the receiver detects the propagation fading is lower than theminimum received level specified by ATPC, the RFCOH is used allow the transmitter to raise thetransmit power Working principle of ATPC

ATPC

Receiver Demodulator

ATPC

Microwave Propagation Anti-Fading Technologies - 4

Transmitter

Receiver

ATPC

Demodulator

Receiver Demodulator

ATPC

Modulator

Modulator

Transmitter Modulator


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ATPCThe output power of the transmitter automatically traces and changes with the received level of thereceiver within the control range of ATPC

The time rate of severe propagation fading is usually small (


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Microwave PrinciplesMicrowave PropagationA i F di T h l i 7

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For diversity, two or multiple transmission paths are used to transmit the same information and the receiver output signals are selected or composed, to reduce the effect of fading.

Diversity has the following types, space diversity, frequency diversity, polarization diversity, and anglediversity.

Space diversity and frequency diversity are more frequently used. Space diversity is economical and has agood effect. Frequency diversity is often applied to multi-channel systems as it requires a wide bandwidth.Usually, the system that has one standby channel is configured with frequency diversity

H f 2

f 1

Anti-Fading Technologies 7Diversity

Space Diversity (SD)

f 1

f 2

Frequency Diversity (FD)


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Microwave Propagation and Anti-Fading Technologies

Microwave PrinciplesDigital Microwave

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Digital Microwave Radio1+1 Hot Stand By configuration

Space Diversity technologies - the configuration of two antennas,

Adopted which improving system availability.

gEquipment Protection 1

Microwave PrinciplesDigital Microwave

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N+1 (N3, 7, 11) ProtectionIn the following figure, M n stands for the active channel and P stands for the standby channel. The active channel and thestandby channel have their independent modulation/demodulation unit and signal transmitting/receiving unit.

When the fault or fading occurs in the active channel, the signal is switched to the standby channel. The channel backupis an inter-frequency backup. This protection mode (FD) is mainly used in the all indoor microwave equipment.

RFSOH

Ch1 Ch2 Ch3

Cp Cp

Ch3 Ch2 Ch1

Products of different vendors support different specifications

gEquipment Protection Modes 2

Switching ControlUnit



Microwave PrinciplesDigital MicrowaveEquipment Protection Modes 3

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Configuration Protection Mode Remarks Application

1 + 0 NP Non-Protection Terminal of the Network

1 + 1 FD Channel Protection Inter-Frequency

Select the proper Mode depending onthe Geographical Conditions andRequirements of the Customer

1 + 1 SD Equipment andChannel Protection

Inter-Frequency

1 + 1 FD + SD Equipment andChannel Protection

Inter-Frequency

M + n FD Equipment andChannel Protection

Inter-Frequency

Large Capacity Backbone


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Importance parameters affecting microwave propagation.

Various factors affecting microwave propagation.

Various fading types in the microwave propagation (free space propagation fading, atmosphericabsorption fading, rain or fog scattering fading, K type fading, multipath fading, duct type fading, andscintillation type fading).

Anti-fading technologies.

Anti-fading measures adopted on the equipment: adaptive equalization, and ATPC.

Anti-fading measures adopted in the system.

Propagation and Anti-Fading TechnologiesSummary

2013 August 7 Microwave Radio Principles

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Transcript of 2013 August 7 Microwave Radio Principles