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