A WidebandImaging Radar For Through-the-Wall Surveillance SPIE 2004

8/8/2019 A WidebandImaging Radar For Through-the-Wall Surveillance SPIE 2004

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A Wideband Imaging Radar For Through-the-Wall

Surveillance

SPIE Defense and Security Symposium

Technologies for Homeland Security and Law Enforcement

15 April, 2004


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IMAGING RADAR DEVELOPMENT ACTIVITIES

Through the wall imaging- funded by National Institute of Justice (NIJ) for law enforcement use

- tactical use in hostage, barricade, suspect search situations- image interior building structure- detect motion of people- standoff capability- demonstrate performance with brassboard system

Perimeter surveillance for security of fixed and mobile assets- funded by Air Force Research Lab (AFRL) Rome Research Site- system simulation and operational analysis

- human and vehicle motion detection at long range- motion detection through coherent scene subtraction- foliage penetration- identify cost and performance drivers


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BRASSBOARD IMAGING RADAR SYSTEM

Portable system

- 20 lb., 2.2 m long, 4 antenna, collapsible array- battery powered

Antenna

Switchbox Radar

Antenna Array


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SYSTEM TECHNICAL CONCEPTS

Range resolution is a function of bandwidth- R = c/2BW- for 1500 MHz BW, range resolution is 0.1 m

Cross range resolution is determined by frequency and aperture size

Fine cross range resolution at long distances requires large antennasand/or higher frequencies of operation- seeing that two people are standing next to one another matters

0

20

40

60

80

100

0 20 40 60 80 100

Detection Range - meters

ArrayAperture-meters

0.2 m

0.5 m

1 m

2 m

5 m

10 m

500 MHz

0

20

40

60

80

100

0 20 40 60 80 100

Detection Range - meters

ArrayAperture-meters

0.1 m

0.2 m

0.5 m

1 m

2 m

5 m

10 m

1000 MHz


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LOW OPERATING FREQUENCY REQUIRES APERTURE SYNTHESIS

Moving a single antenna is impractical for most through wall situations

A multiple antenna array improves cross range resolution significantly- scanning the array further improves resolution by a factor of two

Brassboard operational concept is a stationary system that scans anantenna array to get data to synthesize a 2D image


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TEST CONFIGURATIONS - THROUGH THE WALL


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INTERIOR WALL RESULTS

studs

wallconfiguration

three parallelwalls

tree

buriedconcrete

block

Experimental data shows theeffectiveness of increasing theaperture of the sensor system

All current through the wall sensorsused fixed antennas

However, the imaging algorithms do notrequire use of a fixed array

Interior walls are relatively easy to seethrough

Note : 0.05 m wide stud appears to be 0.2 m wide at a distance of 4.6 mfrom radar, illustrating effect of cross range resolution on image quality


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REINFORCED CONCRETE WALL RESULTS

12 exterior poured, steel

reinforced concrete wall

radar on inside of

room pointing out

person 2

person 1

Attenuation and dispersioncomplicate image formation

Without correction fordispersion, images become

defocused

Only frequency domain sensingmethods allow for frequency

dependent dispersioncorrection


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REINFORCED CONCRETE WALL RESULTS

corner reflections

UCSB lecture hall

Strong corner reflectionsfrom external wall supportsseen in background image

Background subtraction

shows image of three trashcans in triangle and two

people

person 2

person 1

metal trash cans


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AKELATEST CONFIGURATION - FOLIAGE PENETRATION


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TEST CONFIGURATION -FOLIAGE PENETRATION


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SELECTED RESULTS

person in brush at 40 m Data taken on detection of individuals

through various types of foliage

Distances of 32, 34, 38, 40, 44, 46 meters

Breezy day with moving foliage

Attenuation due to foliage ~ 20dB (similarto three interior walls)


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MAJOR AREAS IDENTIFIED FOR IMPROVEMENT

Increase speed of radar- allows motion detection at realistic rates- allows better imaging through signal averaging

Increase speed of display and processing- required to handle increased data rate of faster radar

Antenna array may ultimately limit overall system performance

- more robust array concept needed


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CURRENT DEVELOPMENT HARDWARE

500 - 2000 MHz 10 sec per point software defined 50 mW power output ~ $1,000 parts cost

Antenna connectorsPower conditioner

Radar interface

Radar Tx/Rx

4 diameter

1.5 tall ~ 13 watts battery powered 2.25 lbs w/battery


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8 ANTENNA INTERFACE BOARD

Antenna switch network allows scanningof up to 8 antennas

- uses only a single radar- wired operation- same operational concept as TTW

brassboard- low cost, early option for field use

Board mates to radar through two RFconnectors- plug interface allows development of

boards with special characteristicswithout requiring modification ofradar


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FREQUENCY BAND OMISSION DURING TRANSMISSION

FCC restrictions require strict control of transmission frequencies- the ability to selectively notch frequencies will help with licensing

Frequencies to notch selected by user from control interface


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STATIC IMAGE

person

wall

Image taken from single frame of breathing test


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MORE RESULTS

Tests recently completed on a series of 5 walls- drywall, brick faced, concrete block, adobe, reinforced concrete- all walls 12 thick

Breathing response detected through each wall- drywall: at 19 from standoff of 12- brick: at 21 from standoff of 14- concrete block: at 28 from standoff of 21

- adobe: at 16 from standoff of 4- reinforced concrete: at 22 from standoff of 10


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CONCLUSION

Physics and technology for through-the-wall imaging are wellunderstood

- no fundamental principles limit success- commercial technology exists for implementing a robust system

Imaging and motion detection algorithms have been demonstrated withreal data

Improvements in radar operation are extending the operational rangeand sensitivity of through-the-wall imaging systems

Documents

A WidebandImaging Radar For Through-the-Wall Surveillance SPIE 2004