Effective imaging of buried dielectric objects

Ultrawide-band CW radar have shown good potential for remote imaging of surface laid or shallow buried landmine-like objects. However when sensing fields near to the ground, a number of factors including direct antenna coupling, air/ground coupling, receiver noise floor, and effective dynamic range conspire to degrade or mask the scattered return, resulting in a loss of signal magnitude, range accuracy, and range resolution. The present paper addresses the latter problems using a near-field detection methodology and providing a thorough experimental and systems analysis of the signal-to-clutter issues. The method proves advantageous in sensing weak echoes in the vicinity of the sensor from objects of low dielectric contrast with their environment. To enhance image processing gains, an effective space frequency synthetic aperture technique applicable to the two-media problem is outlined. The algorithm is straightforward and robust enough to be implemented on compact GPR systems operating in real time. The remaining problem of object identification will not be addressed here. To demonstrate the utility of these combined techniques, field experiments, over different frequency bands, were conducted and their results are reported.