Radar 2009 A_10 Radar Clutter1

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Transcript of Radar 2009 A_10 Radar Clutter1

Radar Systems Engineering Lecture 10 Part 1 Radar ClutterDr. Robert M. ODonnell IEEE New Hampshire Section Guest Lecturer

IEEE New Hampshire SectionRadar Systems Course 1 Clutter 11/1/2009

IEEE AES Society

Block Diagram of Radar SystemPropagation Medium Target Radar Cross Section AntennaBuildings (Radar Clutter)

Transmitter Power Amplifier T/R Switch Waveform Generation

Signal Processor Computer Receiver A/D Converter Pulse Compression Clutter Rejection (Doppler Filtering)

User Displays and Radar Control

General Purpose Computer

Tracking Data RecordingPhoto Image Courtesy of US Air Force Used with permission.Radar Systems Course Clutter 11/1/2009 2

Parameter Estimation

Thresholding

Detection

IEEE New Hampshire Section IEEE AES Society

Outline

Motivation Backscatter from unwanted objects Ground Sea Rain Birds and Insects

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

Why Study Radar Clutter?Naval Air Defense Scenario

Chaff Bird Flock Rain

Targets

Sea TargetCourtesy MIT Lincoln Laboratory Used with permission

Ground Urban Buildings

Ground Hills

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

Radars for Which Clutter is a IssueAEGIS SPY 1Courtesy of ITT Gillfillan Used with permission

SPS-48

SPS-49

Courtesy of US Navy

Courtesy of US Navy

AWACS E-3A

OTH Radar

Courtesy of Raytheon Used with permission

Courtesy of US Navy

HAWKEYE E-2C

Courtesy of US Air Force

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

Radars for Which Clutter is a IssueCourtesy of US Air Force

JOINT STARS E-8

AEROSTAT RADAR

APG-63 V(2) F-16 APG-68

Courtesy of Alphapapa

Courtesy of Boeing Used with permission

Courtesy of Northrop Grumman Used with permission

FAA ARSR-4

TPS-79

WEDGETAIL

Courtesy of Lockheed Martin Used with permission

Courtesy of Wings777

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

How to Handle Noise and Clutter

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

How to Handle Noise and ClutterIf he doesnt take his arm off my shoulder Im going to hide his stash of Hershey Bars !!

Why does Steve always talk me into doing ridiculous stunts like this ?

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IEEE New Hampshire Section IEEE AES Society

Typical Air Surveillance Radar(Used for Sample Calculations) Radar ParametersFrequency

FAA - Airport Surveillance RadarInstrumented range Peak power Average power Pulse repetition frequency Antenna rotation rate Antenna sizeCourtesy of MIT Lincoln Laboratory Used with permission

S-band (27002900 MHz) 60 nautical miles 1.4 mw 875 W (7001200 Hz) 1040 Hz average 12.8 rpm 4.8 m 2.7 m 33 dB

Antenna gain

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

Outline Motivation Backscatter from unwanted objects Ground Sea Rain Birds and Insects

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

Outline - Ground Clutter Introduction Mean backscatter Frequency Terrain type Polarization

Temporal statistics Doppler spectra

Radar Systems Course Clutter 11/1/2009

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IEEE New Hampshire Section IEEE AES Society

Attributes of Ground ClutterMean value of backscatter from ground clutter Very large size relative to aircraft Varies statisticallyFrequency, spatial resolution, geometry, terrain type

Doppler characteristics of ground clutter return Innate Doppler spread small (few knots)Mechanical scanning antennas add spread to clutter

Relative motion of radar platform affects Doppler of ground clutterShip Aircraft

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IEEE New Hampshire Section IEEE AES Society

Ground Based Radar DisplaysMountainous Region of Lakehead, Ontario, Canada PPI Set for 30 nmi. Plan Position Indicator (PPI) Display

Map-like Display Radial distance to center Angle of radius vector Threshold crossingsRadar Systems Course Clutter 11/1/2009 13

Range Azimuth Detections

0 dBShrader, W. from Tutorial on MTI Radar presented at Selenia, Rome, Italy. Used with permission.

IEEE New Hampshire Section IEEE AES Society

Photographs of Ground Based Radars PPI(Different Levels of Attenuation)Mountainous Region of Lakehead, Ontario, Canada PPI Set for 30 nmi.

Attenuation Level 0 dB

Attenuation Level 60 dB

Shrader, W. from Tutorial on MTI Radar presented at Selenia, Rome, Italy. Used with permission.

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IEEE New Hampshire Section IEEE AES Society

Photographs of Ground Based Radars PPIDifferent Levels of Attenuation0 dB 0 dB 10 dB 40 dB 50 dB

Shrader, W. from Tutorial on MTI Radar presented at Selenia, Rome, Italy. Used with permission.Radar Systems Course Clutter 11/1/2009 15

20 dB

30 dB

60 dB

70 dB

IEEE New Hampshire Section IEEE AES Society

Geometry of Radar ClutterRadar

Elevation Viewh cT / 2

cT sec

Plan ViewRadar

B

Clutter

R B

0 =

A

A = RB [ cT sec ]

Courtesy of MIT Lincoln Laboratory Used with permission

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IEEE New Hampshire Section IEEE AES Society

Calculation of Ground Clutter0.01 m2 Typical Value of o = -20 dB = m2 cT Clutter = o A = o R B 2 For ASR-9 (Airport Surveillance Radar) cT = 100m B = 1.5o = 0.026 radians R = 60 km 2 0.01 m2 x 100 m x 60,000 m x 0.026 radians = 1500 m2 Clutter = 2 m For Target = 1 m2Small single-engine aircraft

Target

INPUT

Clutter

=

1 1500

OUTPUT Target

Clutter

= 20For good detection

M ust suppress clutter by a factor of 1500 x 20 = 30,000 = 45 dB

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IEEE New Hampshire Section IEEE AES Society

Courtesy of MIT Lincoln Laboratory Used with permission

Joint U.S./Canada Measurement Program

Phase One radar VHF, UHF, L-, S-, X-bands

42 sites Data shared with Canada and the United Kingdom

Measurements conducted 1982 1984 Archival data at Lincoln Laboratory18

Courtesy of MIT Lincoln Laboratory Used with permission

Radar Systems Course Clutter 11/1/2009

IEEE New Hampshire Section IEEE AES Society

Joint U.S./Canada Measurement ProgramPhase One Radar Radar System ParametersFrequency Band MHz) Antenna Gain (dB) Antenna Beamwidth Az (deg) El (deg) Peak Power (kW) Polarization PRF (Hz) Pulse Width (s) Waveform A/D Converter Number of Bits Sampling Rate (MHz) VHF 13 13 42 10 HH,VV 500 UHF 25 5 15 10 HH,VV 500 L-Band 28.5 3 10 10 HH,VV 500 S-Band 35.5 1 4 10 HH,VV 500 X-Band 38.5 1 4 10 HH,VV 500

0.1, 0.25, 0.1, 0.25, 0.1, 0.25, 0.1, 0.25, 0.1, 0.25, and 1 and 1 and 1 and 1 and 1 Uncoded Uncoded Uncoded Uncoded Uncoded CW CW CW CW CW Pulse Pulse Pulse Pulse Pulse 13 10, 5, 1 13 10, 5, 1 13 10, 5, 1 13 10, 5, 1 13 10, 5, 1

Courtesy of MIT Lincoln Laboratory

Adapted from Billingsley, Reference 2

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Clutter Physics

H Depression Visible Angle Terrain

R

MicroshadowingClutter Coefficient o

Courtesy of MIT Lincoln Laboratory Used with permissionRadar Systems Course Clutter 11/1/2009 20

IEEE New Hampshire Section IEEE AES Society

Histograms of Measured Clutter Strength oF4 (dB)1050 90 99

Forest X Band

10

50

90 99

Forest VHF

Percent

o F 4 = 24 dB5 5

o F 4 = 11 dB

Blue Line Is Mean

0-70 -60 -50 -40 50

F4 (dB)

-30

-20 90

-10

0 -70 99

0

-60 50

10

Farmland X Band

10

-50 -40 -30 4 90F (dB) 99

-20

-10

0

Farmland VHF

Percent

o F 4 = 23 dB5 5

o F 4 = 55 dB

0

-80

-70

-60

-50

-40

-30

-20

-10

0

-80

-70

-60

F4 (dB)Radar Systems Course Clutter 11/1/2009 21

F4 (dB) IEEE New Hampshire Section IEEE AES Society

-50

-40

-30

-20

-10

Clutter PhysicsClutter Histogram Weibull Parametersa w (A)

H Depression Visible Angle Terrain

R

o (f) w

oF 4 (dB)

MicroshadowingClutter Coefficient o

Courtesy of MIT Lincoln Laboratory Used with permissionRadar Systems Course Clutter 11/1/2009 22

IEEE New Hampshire Section IEEE AES Society

Weibull Probability Density Functionx 50 =Median value of

x

b (log 2 2 ) x b 1 p(x ) = e b x 50

log 2 x b xb 50

b = 1 / aw aw =Weibull shape parameter In units of m2/m2

x = oF4

The Weibull and Log Normal distributions are used to model ground clutter, because they are too parameter distributions which will allow for skewness (long tails) in the distribution of ground clutter For a w = 1 , the Weibull distribution degenerates to an Exp