EM GroupEM Group

LOW-COST, HIGH RESOLUTION X-BAND LABORATORY RADAR SYSTEM FOR SYNTHETIC

APERTURE RADAR APPLICATIONS

Electromagnetics Research Group

G.L. Charvat, PhD Candidate

Electromagnetics Research GroupDept. of Electrical and Computer Engineering

Michigan State University

EM GroupEM GroupMotivation and Overview of

Presentation

• Motivation: To self-study SAR imaging technology by developing hardware and algorithms for the eventual application of through-lossy dielectric imaging.

• Fundamentals of Radar• High Resolution Radar Imaging: Synthetic Aperture Radar (SAR)• Chirped Radar• Greg's manufacturing process• Two Small Aperture Linear Rail SAR Imaging Systems

o The Unique Approach to Frequency Modulated Continuous Wave Radaro The Low-Cost, High Resolution X-band Laboratory Radar System for

Synthetic Aperture Radar Applications• Image formation algorithms• SAR Imagery (of unusual targets)• Current Research: Through-lossy dielectric imaging• Discussion

EM GroupEM GroupFundamentals of RAdio Direction

And Range (RADAR)

• A transmitter sends out a pulse of radio frequency (RF) energy.

• Pulse of radio waves goes out to an unknown object (target) at some distance from the transmitter.

• Pulse hits target, and reflects off target (like shining a flashlight at something in the night, reflection occurs).

• Reflected pulse travels back towards the transmitter, where, placed next to that transmitter is a receiver.

• The reflected pulse is detected by the receiver.

• This pulse takes time to make a round trip.

• Pulse travels at the speed of light.

• So, we time this pulse like a stop watch, using our receiver as the start/stop and an oscilloscope as the time indicator

EM GroupEM Group The A-Scope

• In order to time the range to target you could use an oscilloscope.

• This configuration was used widely in WW2, and is known as the A-Scope

• The radar antenna was manually rotated to find target direction, with the A-Scope indicating range. Radar images were manually drawn out by the operator.

The SCR270, tracking the Japanese strike force in route to bomb Pearl Harbor:

EM GroupEM GroupThe Plan Position Indicator

(PPI)• In order to build an image of the target scene in and around the radar system,

the radar system could automatically rotate its antenna and plot its A-scope data on a polar plot.o This technique is known as the PPI display.

EM GroupEM GroupSynthetic Aperture Radar (SAR)

Imaging

• SAR in general: A radar system traverses a known path acquiring numerous range profiles (A-Scope data) which are then applied to an image formation algorithm resulting in a high resolution radar image equivalent to a very large real aperture.

• Typical application: Airborne SAR reconnaissance imaging.• Application discussed in this presentation: small aperture SAR.

Collection geometry.Airborne SAR: most common application

(image from Sandia National Laboratory, Albuquerque International Airport at Ku band)

Small aperture rail SAR: typical application in measuring RCS of aircraft.

EM GroupEM Group Principles of FMCW Radar

• Small linear rail SAR systems typically use FMCW, and this is the case for the research presented in this paper.

• FMCW radar provides range to target information in the form of low frequency (near audio) beats. This is easier than time domain data acquisition.o This is done by frequency modulating a transmit oscillator, and comparing the

current transmitted carrier to the carrier which is reflected from the targeto The closer a target, the lower the beat frequencyo The further a target, the higher the beat frequency

EM GroupEM Group Manufacturing Process

1. Acquire old junk from radio swap meet.

2. After some work in the lab...

3. Complete radar system, ready for imaging.

EM GroupEM GroupThe MA87127-1 ‘Gunnplexer’ and the

Unique Approach to FMCW Radar

This solution allowed for a very low cost FMCW Radar design for high volume automotive applications (pre-UWB).

Center frequency of 10.25 GHz, chirp BW of 70 MHz, transmit power 10 dBm, front end NF = 10 dB

EM GroupEM GroupThe Unique Approach to FMCW

Radar

EM GroupEM GroupThe Unique Approach to FMCW:

Range Profile Results

30 dBsm trihedral corner reflector at 25 ft 30 dBsm trihedral corner reflector at 40 ft

EM GroupEM GroupThe Unique Approach to FMCW:

Data Collection Geometry

EM GroupEM Group Image Formation Algorithms

A range stacking algorithm. In this experiment a 20 dBsm trihedral corner reflector was placed 25 ft down range from the rail, and a 30 dBsm trihedral corner reflector was placed 40 ft downrange.

The PFA with narrow beamwidth and narrow bandwidth assumptions. A target scene was setup with a 20 dBsm trihedral corner reflector located 25 ft downrange, and a 30 dBsm trihedral corner reflector located 65 ft downrange.

EM GroupEM Group Image Formation Algorithms

Target scene: 20 dBsm trihedral corner reflector located 25 ft downrange, and a 30 dBsm trihedral corner reflector located 65 ft downrange.

PFA:

RMA:

EM GroupEM GroupThe Low-Cost, High Resolution, X-Band

Laboratory Radar System for SAR Applications

Specifications:

TX: 15 dBm

RX dynamic range 60 db

Chirp: 8 GHz to 12.4 GHz

EM GroupEM Group

The Low-Cost, High Resolution, X-Band Laboratory Radar System for SAR Applications

Range Profile Data

Seven 0 dBsm cylinders spaced ever 1 ft

Seven 0 dBsm cylinders spaced ever 2 ft

Target scene in February…

Only 2.4 GHz of chirp bandwidth used here:

EM GroupEM GroupThe Low-Cost, High Resolution, X-Band Laboratory Radar System: Rail SAR Implementation (the $240

Genie garage door opener based rail SAR)

EM GroupEM GroupAdditional SAR Image Improvement

Algorithms

• Motion Compensation Algorithms (MOCOMP), developed for data simulation only.

Downrange and cross range motion error compensation developed.

Simulations conducted to determine mechanical tolerances of the linear rail.

80 mils max downrange error.

• Map Drift (MD) autofocus algorithm

EM GroupEM GroupSAR Imagery of Pushpins and

4.37mm Spheres

pushpin

row of 4.37mm diameter spheres

EM GroupEM Group SAR Imagery of Model Airplanes

1:72 scale model B52

1:32 F14

EM GroupEM Group SAR Image of a 5.0 Mustang

EM GroupEM Group SAR Imagery of a Bike

Greg’s bike on radar.

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A Theoretical Model of a Lossy Dielectric Slab for the Characterization of Radar System

Performance Specifications

A ‘broad side of the barn’ scenario

The ultimate small aperture SAR application: try to image a target on the other side of a lossy dielectric.

We first must examine the ‘broad side of the barn’ scenario to determine the minimum system performance specifications.

EM GroupEM Group Conclusions and Future Work

• Two rail SAR imaging systems were developed.• Four imaging algorithms were developed.• Image improvement algorithms were developed.• High resolution SAR imagery was created of various

objects.• Ongoing efforts in SAR imaging through a lossy

dielectric.• For more information, please visit

www.msu.edu/~charvatg or contact charvatg@msu.edu