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ECEN5633 Radar TheoryECEN5633 Radar TheoryLecture #1 13 January 2015Lecture #1 13 January 2015Dr. George ScheetsDr. George Scheetswww.okstate.edu/elec-eng/scheets/ecen4533www.okstate.edu/elec-eng/scheets/ecen4533
ECEN5633 Radar TheoryECEN5633 Radar TheoryLecture #1 13 January 2015Lecture #1 13 January 2015Dr. George ScheetsDr. George Scheetswww.okstate.edu/elec-eng/scheets/ecen4533www.okstate.edu/elec-eng/scheets/ecen4533
Read Chapter 1.1 – 1.4Read Chapter 1.1 – 1.4 Ungraded Homework Problems: 1.1, 2, & 4Ungraded Homework Problems: 1.1, 2, & 4
Technical Problems? Call (405)744-7234
ECEN5633 Radar TheoryECEN5633 Radar TheoryLecture #2 15 January 2015Lecture #2 15 January 2015Dr. George ScheetsDr. George Scheetswww.okstate.edu/elec-eng/scheets/ecen5633www.okstate.edu/elec-eng/scheets/ecen5633
ECEN5633 Radar TheoryECEN5633 Radar TheoryLecture #2 15 January 2015Lecture #2 15 January 2015Dr. George ScheetsDr. George Scheetswww.okstate.edu/elec-eng/scheets/ecen5633www.okstate.edu/elec-eng/scheets/ecen5633
Read Chapter 1.5 – 1.7Read Chapter 1.5 – 1.7 Problems 1.5, 1.6, 1.9Problems 1.5, 1.6, 1.9 Quiz #1, 29 JanuaryQuiz #1, 29 January
Big BangBig Bang 13.84 13.84 ++ 0.04 billion years ago 0.04 billion years ago
Picture of Universe Moments Before the Big Bang
James Clerk MaxwellJames Clerk Maxwell
Born 1831Born 1831 Died 1879Died 1879 Scottish Mathematical Scottish Mathematical
PhysicistPhysicist 1865 Maxwell's Equations1865 Maxwell's Equations
Electricity, magnetism, & optics Electricity, magnetism, & optics part of same phenomenapart of same phenomena
Source: Wikipedia
Heinrich HertzHeinrich Hertz
Born 1857 Born 1857 Died 1894Died 1894 German PhysicistGerman Physicist Provided conclusive Provided conclusive
experimental proof experimental proof EM waves reflect off EM waves reflect off some materialssome materials
Source: Wikipedia
Radio waves deflected off a RAF BomberRadio waves deflected off a RAF Bomber Robert Watson-WattRobert Watson-Watt
Head, UK Radio Research StationHead, UK Radio Research Station February 1935February 1935
6 MHz BBC signal6 MHz BBC signal
Source: Wikipedia
Chain Home RadarChain Home Radar
Pulse RadarPulse Radar ffcc = 22-25 MHz = 22-25 MHz
PPpeakpeak = 200 Kw = 200 Kw
TTpulsepulse = 5 - 25 = 5 - 25μμsecsec
PRF = 25 or 50 ppsPRF = 25 or 50 pps
Source: Wikipedia
WWII German RadarsWWII German Radars
"Freya" Pulse Radar"Freya" Pulse Radar ffcc = 120 -130 MHz = 120 -130 MHz
PPpeakpeak = 15 -20 Kw = 15 -20 Kw
TTpulsepulse = 3 = 3 μμsecsec
PRF = 500 ppsPRF = 500 pps
Could not detect altitudeCould not detect altitudeSource: Wikipedia
WWII German RadarsWWII German Radars
"Wurzburg" Pulse Radar"Wurzburg" Pulse Radar ffcc = 560 MHz = 560 MHz
PPpeakpeak = 8 Kw = 8 Kw
TTpulsepulse = 2 = 2 μμsecsec
PRF = 1,875 ppsPRF = 1,875 pps
Height Finding & Height Finding & Gun LayingGun Laying
Source: Wikipedia
German Night Fighterscirca 1942 - 1943
German Night Fighterscirca 1942 - 1943
Very Short RangeVery Short Range
Source: Wikipedia
U.S. Night FighterU.S. Night Fighter
P-61 Black WidowP-61 Black Widow DeployedDeployed
OperationallyOperationallyin 1944in 1944
Crew of 3Crew of 3
Source: Wikipedia
Proximity FuzeProximity Fuze
CW radar inside an AAA projectile
Operated on Doppler Effect
1st kill in January, 1943
Source: Wikipedia
WWII Window (Chaff)WWII Window (Chaff)
Source: aess.cs.unh.edu
PPI display of chaffPPI display of chaffSeveral minutes after dropSeveral minutes after drop Cut to ½ Cut to ½ λλ
WWIIWWIILancaster dropping chaffLancaster dropping chaff
Rapid Blooming ChaffRapid Blooming Chaff Now standard defensive gearNow standard defensive gear
Against Radar Against Radar Guided MissilesGuided Missiles
Navy ShipsNavy Ships Combat AircraftCombat Aircraft
Source: Wikipedia &Aerospaceweb.org
Airborne Jammer Radar Set AN/APT-1Airborne Jammer Radar Set AN/APT-1
Pout < 240 wattsSource: lonesentry.com
Phased Array RadarPhased Array Radar Electronically Steerable BeamsElectronically Steerable Beams 1944 German Mammut1944 German Mammut
6 to 8 fixed Freya antennas6 to 8 fixed Freya antennas Steerable over 100 degree arcSteerable over 100 degree arc
Rare until 70'sRare until 70's Common NowCommon Now
Pave PawsPave Paws AegisAegis
Source: Wikipedia
Steerable Beam ExampleSteerable Beam Example
fc = 300 MHzλ = 1 meter
Same signal fedto both antennas.
Beam shoots outboth sides at 90degree angle.
Directivity Strength
λ/2
MIMO ExampleMIMO Example
fc = 300 MHzλ = 1 meter
Signal to leftantenna advancedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
MIMO ExampleMIMO Example
fc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
MIMO ExampleMIMO Example
fc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 833.3 picosecond( = 25% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
MIMO ExampleMIMO Example
fc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 1 2/3 nanosecond( = 50% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
Look Down, Shoot DownLook Down, Shoot Down Standard Pulse RadarStandard Pulse Radar
Low Altitude target Low Altitude target obscured by ground obscured by ground clutter.clutter.
Pulse Doppler RadarPulse Doppler Radar Subtract out anything Subtract out anything
inbound at 400 knotsinbound at 400 knots Moving Target will stick Moving Target will stick
outout Unless…Unless…
400 knots
Low Altitude
High Altitude
Synthetic Aperture RadarSynthetic Aperture Radar
11stst Successful Image Successful Image15 meter resolution15 meter resolutionWillow Run Airport, MichiganWillow Run Airport, Michigan
Source: Wikipedia
SAR Image (4" resolution)SAR Image (4" resolution)
Source: aess.cd.unh.edu
F-117 NighthawkF-117 Nighthawk
Source: Wikipedia
Impulse Response
Non-stealthvs
Stealth
Impulse Response
Non-stealthvs
Stealth
Source: Cheville & Grischkowsky,"Time Domain THz Impulse Response Studies", Applied Physics Letters, October 1995
Christian DopplerChristian Doppler Austrian Mathematician & PhysicistAustrian Mathematician & Physicist Born 1803Born 1803 Died 1853Died 1853 Paper "Paper "On the coloured light On the coloured light
of the binary stars and some of the binary stars and some other stars of the heavensother stars of the heavens""postulated speeds of stars postulated speeds of stars changed the color of their changed the color of their light.light.
Source: Wikipedia
Last TimeLast Time Selected Historical Radar HighlightsSelected Historical Radar Highlights Speed of EM wavesSpeed of EM waves
Vacuum: 299.8(10Vacuum: 299.8(1066) m/sec) m/sec Air: ≈ 299.7(10Air: ≈ 299.7(1066) m/sec) m/sec Approximation OK to use: 3(10Approximation OK to use: 3(1088) m/sec) m/sec
Fourier Transform TheoryFourier Transform Theory x(at) ↔ X(f/a)/|a|x(at) ↔ X(f/a)/|a|
a < 1 → freq spread ↓ & center frequency goes downa < 1 → freq spread ↓ & center frequency goes down a > 1 → freq spread ↑ & center frequency goes upa > 1 → freq spread ↑ & center frequency goes up
Previous Class – Doppler ShiftPrevious Class – Doppler Shift s(t) transmitted?s(t) transmitted? r(t) = As(t – RTT) if target stationaryr(t) = As(t – RTT) if target stationary
A << 1.0A << 1.0 r(t) = As(r(t) = As(ααt – t – RTT RTT ++ 2vrto/c) if radial vr ≠ 0
α = 1 – 2vr/c < 1.0 if target moving awayReceived pulse length > transmitted
α = 1 + 2vr/c > 1.0 if target approachingReceived pulse length < transmitted
Yellow terms = time delayPhase shift in frequency domainto = time leading pulse edge hits targetPulse transmitted at t = 0 seconds
Frequency DomainFrequency Domain
Car approaching at 50 mph = 22.35 m/secCar approaching at 50 mph = 22.35 m/sec x(at) ↔ X(f/a)/|a|; a = 1 2vx(at) ↔ X(f/a)/|a|; a = 1 2vrr/c/c
- if moving closer- if moving closer + if moving away+ if moving away
a =1 - 2va =1 - 2vrr/c /c
= 1 – 2(22.34)/(2.997*10 = 1 – 2(22.34)/(2.997*1088) = 0.99999985) = 0.99999985 fftransmittedtransmitted = 10.52 GHz? = 10.52 GHz?
ffreceivedreceived = 10.52 GHz/0.999999851 = 10.52 GHz/0.999999851
= 10,520,00= 10,520,001,568 1,568 HzHz
-+
Doppler Effect 60 mph (26.8 m/sec), 2 m offset, 1.2 GHz
Doppler Effect 60 mph (26.8 m/sec), 2 m offset, 1.2 GHz
Parabolic Directional AntennasParabolic Directional Antennas
Source: Web