MIT Haystack

Build a High-Resolution
Synthetic Aperture Radar
Imaging System in Your
Backyard
by
Gregory L. Char vat
for
MIT Haystack Obser vatory Open Lunch
12 May 2010
1
Synthetic Aperture Radar
(SAR) in Your Backyard
Learn about radar
imaging systems by
building one.
Discover why you
were pulled-over.
head lamps/tail lamps
have greatest RCS on the
5.0 Mustang at X-band
Measure the RCS of
your favorite model
aircraft.
2
Outline
Make a rail SAR
Measured radar imagery
Summary
3
Make a rail SAR
1. 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
Use this realistic architecture:
FMCW rail SAR
x
Linear Rail
L
z
10 dB Directional Coupler
Trig
Antenna
90%
LFM Chirp
Source (VCO)
Motion
10%
Transmit
Antenna
Video
LNA
Amplifier
Receive
MIxer
ADC
Antenna
Frequency Domain
Data
Radar Image
Rail Control
Stepper
Motor
5
Locate/test parts and fabricate
1. 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
3. Fabrication in garage machine
shop
4. Complete radar system
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6
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
7
Test radar sensor
snow
Range profile tests
demonstrate
functionality
0 dBsm pt. tarets
Row of 0 dBsm
point targets
Difficult test
environment due
to snow (February
in East Lansing
Michigan)
8
Find a linear rail
Linear 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!
9
Find a linear rail: low-cost stepper
motor control
2.5 A stepper
Torque required too high
for largest low-cost
stepper motor
motor
Cordless drill planetary
gear transmission reduced
torque by 6
Enabled <2.5 A stepper
motor to be used
Reduced stepper drive
cost
6:1 cordless drill
planetary gear drive
10
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 soft ware
integration
controls stepper motor
drive
radar timing
acquisition/recording
GUI
11
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
12
Build an outdoor range
open space (reduce aliasing and clutter)
styrofoam table
for holding up targets
mow the lawn
to reduce clutter
13
Lawn clutter mitigation
Mow the lawn
Use coherent background subtraction
Do not walk in front of target scene
footprints
14
Radar imagery: 5.0 Mustang
100 cm
15
Radar imagery: bike
50 cm
Cannondale M300
16
Radar imagery: model
aircraft
20 cm
1:48 Scale B52
1:32 Scale F14
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Low RCS imagery
GO STATE in pushpins:
-55 dBsm spheres
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Summary
Radar 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."
Texas: Antennas Measurement Techniques Association conference, October 2006.
Austin
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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