Low-Power S-Band Rail SAR

ABSTRACT

A Low-Power Radar Imaging System

by

Gregory Louis Charvat

A near real-time radar-based imaging system is developed in this dissertation. This system uses the combination of a spatially diverse antenna array, a high sensitivity range-gated frequency-modulated continuous wave (FMCW) radar system, and an airborne synthetic aperture radar (SAR) imaging algorithm to produce near real-time high resolution imagery of what is behind a dielectric wall. This system is capable of detecting and providing accurate imagery of target scenes made up of objects as small as 6 inch tall metallic rods and cylinders behind a 4 inch thick dielectric slab. A study is conducted of through-dielectric slab imaging by the development of a 2D model of a dielectric slab and cylinder. The SAR imaging algorithm is developed and tested on this model for a variety of simulated imaging scenarios and the results are then used to develop an unusually high sensitivity range-gated FMCW radar architecture. An S-band rail SAR imaging system is developed using this architecture and used to image through two different dielectric slabs as well as free-space. All results are in agreement with the simulations. It is found that free-space target scenes could be imaged using low transmit power, as low as 5 picowatts. From this result it was decided to develop an X-band front end which mounts directly on to the S-band rail SAR so that objects as small as groups of pushpins and aircraft models in free-space could be imaged. These results are compared to previous X-band direct conversion FMCW rail SAR work. It was found that groups of pushpins and models could be imaged at transmit powers as low as 10 nanowatts. A spatially diverse S-band antenna array will be shown to be developed for use with the S-band radar; thereby providing the ability for near real-time SAR imaging of objects behind dielectric slabs with the same performance characteristics of the S-band rail SAR. The research presented in this dissertation will show that near real-time radar imaging through lossy-dielectric slabs is accomplished when using a highly sensitive radar system located at a stand-off range from the slab using a free-space SAR imaging algorithm.

Publications

G. L. Charvat, L. C. Kempel, E. J. Rothwell, C. Coleman, and E. L. Mokole, ``A through-dielectric radar imaging system," IEEE Transactions on Antennas and Propagation, vol. 58, Issue 8, pp. 2594-2603, August, 2010.

G. L. Charvat, ``A Low-Power Radar Imaging System," Ph.D. dissertation, Dept. of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, 2007.

Dissertation Defense Power Pointe Slides

Misc. PPT Slide Shows

G. L. Charvat, “A low-power radar imaging system,” The Boston Chapter of the IEEE APS Society, December 11, 2007.

Engineering Notes

S-band YIG oscillator measured data (frequency, amplitude, vs. voltage). 

Measurement slab holding apparatus.

There were a total of 3 SAR imaging systems developed for this dissertation.  The first is an S-band linear rail SAR which is capable of imaging targets in free space and behind lossy dielectric slabs at stand-off ranges.  This system is a linear FM chirped radar, 2-4 GHz, using 10 milli-watts of transmit power, sensitivity of better than -125 dBm.  All hardware was developed in my basement laboratory/garage machine shop.

There were a total of 3 SAR imaging systems developed for this dissertation.  The first is an S-band linear rail SAR which is capable of imaging targets in free space and behind lossy dielectric slabs at stand-off ranges.  This system is capable of SAR imaging 6” tall carriage bolts in free space using only 5 pico-watts of transmit power.  It is capable of imaging groups of 6” tall carriage bolts or groups of aluminum soda cans behind a lossy dielectric slab using only 10 milli-watts of transmit power at a 30’ stand-off range from the slab.  Shown here are SAR images of targets in free space at various levels of transmit power, and targets behind a lossy dielectric slab.  Also shown here are the actual target scenes with various radar placements and dielectric slabs.