Build a High-Resolution Synthetic Aperture Radar

Imaging System in Your Backyard

byGregory L. Charvat

forMIT Haystack Observatory Open Lunch

12 May 2010

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Synthetic Aperture Radar (SAR) in Your Backyard

Learn about radar imaging systems by building one.

Discover why you were pulled-over.

Measure the RCS of your favorite model aircraft.

head lamps/tail lamps have greatest RCS on the 5.0 Mustang at X-band

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Outline

Make a rail SAR

Measured radar imagery

Summary

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Make a rail SAR1. Use a realistic architecture

2. Locate parts at hamfests.

3. Design radar sensor around available parts

4. Test radar sensor

5. Find a linear rail

6. Develop data acquisition system

7. Write SAR algorithm

8. Build outdoor range

9. Make images!4

LFM ChirpSource (VCO)

90%

10%

10 dB Directional Coupler

Trig

ADC

LNA

MIxer

Video

Amplifier

Linear Rail

Stepper

Motor

Frequency Domain

Data

Rail Control

Antenna

Motion

x

Transmit

Antenna

Receive

Antenna

L z

Use this realistic architecture: FMCW rail SAR

Radar Image

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Locate/test parts and fabricate1. Microwave parts are difficult to find at low costs. Visit your local Hamfests

2. Test to see what actually works, let this drive your design

4. Complete radar system3. Fabrication in garage machine shop

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Radar sensor built from

hamfest parts

LFM stretch mode

Pulse compression

7.5-12.5 GHz chirp in 10 ms

+15 dBm TX Power

15 dBi horns, +- 25 deg E and H plane

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Test radar sensor

Range profile tests demonstrate functionality

Row of 0 dBsm point targets

Difficult test environment due to snow (February in East Lansing Michigan)

snow

0 dBsm pt. tarets

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Find a linear railLinear rails are expensive

The longer the better

typically $10K for an 8’ long rail

Low-cost substitute:

Genie screw-drive garage door opener

Cost = Free!

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Find a linear rail: low-cost stepper motor control

Torque required too high for largest low-cost stepper motor

Cordless drill planetary gear transmission reduced torque by 6

Enabled <2.5 A stepper motor to be used

Reduced stepper drive cost

2.5 A steppermotor

6:1 cordless drillplanetary gear drive

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Develop a data acquisition system(relatively) low-cost NI PCI-6014

16 bit 200 KSPS ADC

10 bit 10 KSPS DAC (use for LFM modulation)

Labview

rapid software integration

controls stepper motor drive

radar timing

acquisition/recording

GUI

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Develop algorithm

Preferred SAR algorithm for the rail SAR in Chapter 5:

W. G. Carrara, R. S. Goodman, R. M. Majewski, Spotlight Synthetic Aperture Radar Signal Processing Algorithms, Artech House Inc., Noowod MA, 1995.

Code this up in MATLAB

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Build an outdoor range

styrofoam tablefor holding up targets

open space (reduce aliasing and clutter)

mow the lawn to reduce clutter

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Lawn clutter mitigationMow the lawn

Use coherent background subtraction

Do not walk in front of target scene

footprints

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Radar imagery: 5.0 Mustang

100 cm

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Radar imagery: bike

50 cm

Cannondale M300

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Radar imagery: model aircraft

20 cm

1:32 Scale F141:48 Scale B52

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Low RCS imagery

-55 dBsm spheresGO STATE in pushpins:

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SummaryRadar built from junk at hamfests

Learn

radar system design

radar imaging techniques

what causes you to get pulled over

High performance at low-cost

Next steps? Build your own!

For more info goto www.mit.edu/~gr20603 (click on Synthetic Aperture Radar)

References:G. L. Charvat. "Low-Cost, High Resolution X-Band Laboratory Radar System for Synthetic Aperture Radar Applications." Austin Texas: Antennas Measurement Techniques Association conference, October 2006. G. L. Charvat, L. C. Kempel. “Low-Cost, High Resolution X-Band Laboratory Radar System for Synthetic Aperture Radar Applications.” East Lansing, MI: IEEE Electro/Information Technology Conference, May 2006.

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