D. B. Estreich, Ph.D. Sonoma State university€¦ · EE 442 –A Short Introduction to Antennas...
Transcript of D. B. Estreich, Ph.D. Sonoma State university€¦ · EE 442 –A Short Introduction to Antennas...
EE 442 – A Short Introduction to AntennasLecture 5
D. B. Estreich, Ph.D.
Sonoma State university
Antennas 1
Figure D-9 from U.S. Army Field Manual 79-3
2
Summary of Lecture 4 – Page 1
The trigonometric Fourier series for a periodic signal of period T is given by
The complex exponential Fourier series for a periodic signal is
The harmonic components add to the fundamental component to form the modelled
waveform – phase relationships between the fundamental and its harmonics are important.
Simple harmonic motion (SHM) produces sinusoidal waves.
The time domain representation of a signal is related to the frequency domain
representation of that signal by the Fourier transform and its inverse transform.
( )0 0 0 0
n 1
0 0
0 0
0
0
2( ) cos( ) sin( ) ;
1 2( ) ; ( ) cos( ) for 1, 2, 3, .
2and ( )sin( ) for 1, 2, 3, .
=
= + + =
= = =
= =
n n
T T
n
T
n
f t a a n t b n tT
a f t dt a f t n t dt n etcT T
b f t n t dt n etcT
0
0
0
*;
( )
1( ) ;
= −
−− =
=
= =
n
T
n
jn tn
jn t jn n n n ndt
f t C
C f t C C C CT
e
e e
3
Summary of Lecture 4 – Page 2
Continuous periodic waveforms are analyzed and modelled using the Fourier series – but
continuous aperiodic waveforms are analyzed and modelled using the Fourier transform.
The Fourier transform is given by
The
1
( ) ( ) ( ) ; and
1( ) ( ) ( )
2
−
−
−
−
= =
= =
j t
j t
F F f t f t e dt
f t F F F e d
4
Summary of Lecture 4 – Page 3
The next point is . . .
Antennas 5
Antenna Definition
[noun]
An antenna is a conductor by which electromagnetic waves are
sent out or received, consisting commonly of a wire or an
assembly of wires (mesh); also called an aerial.
In radio, an antenna is the interface between radio waves
propagating through space and electric currents moving in
metal conductors, as used by a transmitter or receiver.
In transmission, a radio transmitter supplies an electric current
to the antenna's terminals, and the antenna radiates the energy
from the current as electromagnetic waves (radio waves).
In reception, an antenna intercepts some of the power in a radio
wave which induces an electric current at the terminals of the
antenna. This electric current is applied to the input of the
receiver to be processed and detected.
https://en.wikipedia.org/wiki/Main_Page
Antennas 6
Antenna Categories (Many Categories)Still not a complete
list of antennas
https://www.quora.com/What-are-the-different-types-of-antennas-mounted-on-a-fighter-aircraft
Antennas 7
Antennas Come in Many Sizes and Shapes
FCC Frequency Spectrum Allocation in the US
8
AM Radio
FMVHF
TV
Wi-Fi3G/4G
cellular
UHF
TV
Antennas
3 kHz
300 GHz
https://www.ntia.doc.gov/files/ntia/publications/2003-allochrt.pdf
FCC Frequency Spectrum Allocation in the US
http://www.informit.com/articles/article.aspx?p=2249780
Antennas 9
525 – 1710 kHz
88 – 108 MHz
2.401 – 2.484 GHz
3 kHz
300 GHz
54-216 & 470-890 MHz
800, 900, 1900 MHz bands
Antennas 10
Frequency Spectrum for Cellular Telephony
http://eti2506.elimu.net/Terminal_Equipment/Terminal_Equipment.html
Absolute Radio Frequency Channel Number (ARFCN)Absolute Radio Frequency Channel Number (ARFCN)
Cellular Base Station Antennas
11Antennas
Cellular
antennas
Base Station
Controller
Electrical
Power
3-Sector
Antenna
Array
Antennas 12
Cellular Telephone System
BSC
BTS
BTS
BTS
BTS
BSC
BTS
BTS
BTS
BTS
Register
VLR
MSC GMSC
MSC
VLR
HLRAUC
EIR
Base
Station
Subsystem
Base
Station
Subsystem
BSS
BSS
Gateway
PSTN
PSDN
ISDN
BSS
BSS
BTS = Base Transceiver Station
MSC = Mobile Switching Center
Base
Station
Cell
Stealth Cellular Antennas
Antennas 13
SaguaroCacti makereally goodcover forantennas.
Rock Cover
Artificial Tree Stealth Antennas
A differentroot system
14
Antennas 15
Parabolic Antennas
https://fineartamerica.com/art/parabolic+antenna
Parabolic Antennas for Directionality
Antennas 16
https://medium.com/dish/tech-history-the-
story-behind-stanfords-satellite-dish-
hiking-trail-in-palo-alto-fc44745be409
Stanford UniversityRadio Astronomy Antenna
Radio, TV and microwave link antennas
Direct TV Dish Antenna
Palo Alto, CA
New Mexico's Very Large Array Radio Telescope
https://www.nbcnews.com/storyline/the-big-
questions/what-s-causing-those-
mysterious-bursts-deep-space-n704716
Antennas 17
https://www.slideshare.net/OmarHussein46/parabolic-
antenna-84387301
Antennas 18
https://slideplayer.com/slide/10860820/
24
P dAdP
r
=
dA
+z
-z
P+y
-y
r
Ideal Isotropic Radiating Antenna
The other commonly referenced radiator is the dipole antenna.
.
Antennas don’t create radio energy; they only direct it by diversion or concentration. This directional feature is called gain. Remember – it is simply redirected or focused in its directionality (i.e., directivity).
Antenna Gain: A relative measure of an antenna's ability to direct or concentrate radio frequency energy in a specific direction or pattern. A gain measurement is typically expressed in dBi (Decibels relative to an isotropic radiator) or in dBd (Decibels relative to a dipole radiator).
Antennas 19
Antenna Gain
Antennas 20
Parabolic Antennas have High Gain
Antenna gain is usually
defined as the ratio of
the power produced by
the antenna from a far-
field source on the
antenna's beam axis to
the power produced by
a hypothetical lossless
isotropic antenna
(isotropic means that
radiation is equally
directed in all
directions).
Antennas 21
Parabolic Antennas – Beam Width
For parabolic dish antenna:
Diameter = D; wavelength = ; efficiency = k
The gain is
Half-power beam width is
Effective aperture is
2
10(dB) 10 logD
Gain k
=
Beamwidth 70D
2
Effective aperture 0.64
D
Antennas 22
Concept of Antenna Beam Width
Radiated Side Lobes
Radiated EM PowerMaximum
z
x
y
https://www.pimfg.com/blog/antennas-faq
Antennas 23
The Common Satellite Dish Antenna
https://winegard.com/products/satellite
-tv/roof-mounted-antennas/travler
Antennas 24
DirecTV Satellite Dish Receiver/Antenna
Antenna Used in the First Apple iPhone
Antennas 25
Plastic Cover
removedFolded Antenna
Antennas 26
The Dipole Antenna (1)
Antennas 27
The Dipole Antenna (2)
The antenna is driven sinusoidally by alternating between
voltage polarity and current direction. The alternating
charges create electric fields and time-varying currents
create magnetic fields. These launch by traveling waves
propagating outward from the antenna.
Antennas 28
The Dipole Antenna (3)
Antennas 29
The Dipole Antenna (4)
https://www.pinterest.com/pin/390054017706375781/
Antennas 30
The Dipole Antenna (5)
As typically
shown in class
https://www.everythingrf.com/community/what-is-the-
difference-between-a-monopole-and-dipole-antenna
Antennas 31
Fraunhofer Distance Defines Onset of Far-Field Propagation
The Fraunhofer region (or far-field region) from the antenna is where the
radiation pattern no longer changes shape with distance D (and the fields
decrease as 1/R and power density dies off as 1/R2).
22Fraunhofer distance f
Dd
=
where D is the largest physical dimension
of the antenna, and is the wavelength of
the radiation.
The Fraunhofer region exists only for
distances R >> df . The free-space path
loss equation is valid only when the
distance from the antenna exceeds df .
Antennas 32
http://www.hep.manchester.ac.uk/u/xiaguo/waveoptics/Fresnel%20diffraction.pdf
2a 2
a
2
; Fresnel numberF
aN
L=
L
xx
xx
x
(a)
(b)
Fresnel Diffraction From Square Aperature Changing to Fraunhofer
Antennas 33
https://sqwabb.wordpress.com/2017/02/12/free-your-tv-make-a-
digital-antenna-for-under-10/
HDTV Antenna
North America still has some free TV signals. There are, in fact, 18 over-the-air
(OTA) digital TV channels in the Vancouver, B.C. area alone, including CBC
English and French, CTV, CHEK and Global. (That is as of 2017.)
Antennas 34
Monopole Antenna Derived From Dipole Antenna
https://electronics.stackexchange.com/questions/222071/how-can-i-tune-an-antenna-for-receiving-vhf
Antennas 35
The Yagi Antenna Configuration (Yagi-Uda)
800MHz high gain
antennas improve transmit
and receive cellular signals
used by Verizon, Alltel, US
Cellular, Cellular One,
Cingular, Nextel,
SouthernLINC, Bell
Canada, Telus, Mike and
all other Cellular and iDEN
carriers
https://www.alternativewireless.com/cellular-antennas/yagiantennas.html
Antennas 36
Yagi-Uda Antenna Operates Using Interference
https://en.wikipedia.org/wiki/Yagi–Uda_antenna
Antennas 37
More Elaborate Yagi-Uda Antennas
Quad-Yagi dipole antenna with corner reflector
https://www.wifi-
antennas.com/topic/103-quagi-antenna/
2.4 GHz Wi-Fi outdoor
Yagi antenna (18 element)
with 21 dBi gain
Antennas 38
Phased Array Antennas – Steerable Beam
Each radiating element
is fed with a phase-
shifted signal such that
all the fields from the
group of radiating
elements sum together
to steer the antenna’s
beam.
https://en.wikipedia.org/wiki/Phased_array
Antennas 40
Phased Array Antennas in Military Aircraft
https://www.militaryaerospace.com/rf-analog/article/16720155/air-force-eyes-passive-radar-
surveillance-with-initiative-on-wideband-phased-array-antennas
F-16 Fighting Falcon
41
Phased Array Antennas (Cellular)
Radiating
Element
Antennas
Antennas 42
Questions
http://www.radioarcala.com/wp-content/uploads/2013/03/Arcala_Friedricshaven_June_2009_OH6KN-v0.pdf
Radio Arcala located close to Arctic Circle is an amateur radio
station – consists of 36 Yagi antennas (80 meter and 160 meter)
Tower is 320 feet high.
Finland
Antennas 43
Questions
https://www.123rf.com/photo_7155118_many-colorful-question-
marks-around-the-word.html
Antennas 44
https://www.mro-network.com/engineering-
design/understanding-today-s-antenna-complexities
Weather
Radar
ILS Glideslope
& Localizer
VOR/LOC
Capture
Source: Boeing
Antennas on the Boeing 787 Dreamliner
45
Additional Slides (on Radar)
Radar 46
https://behindthesciences.com/signal-processing/fmcw-radar-matlab-tutorial
FMCW Radar with Doppler Shift Included
Radar 47
https://www.st-andrews.ac.uk/~mmwave/mm-waves/avtis/theory-mmw-imaging/radar/
FMCW radar: (a) Frequency Modulated Continuous Wave signal in the time domain (b) Frequency modulation waveform: the time offset delta t between the transmitted (Tx) and received (Rx) signals is set by the distance to reflector (c) The difference or Intermediate Frequency (fIF) is then proportional to range, R
Radar 48
https://www.researchgate.net/figure/Measurement-principle-in-a-
FMCW-lidar_fig1_228372604