SIXTH ANNUAL
ASAP '98 WORKSHOP

Adaptive Dual Aperture
Clutter Cancellation

Abstract The DARPA Moving Target Exploitation (MTE) Program seeks to develop the technology to classify moving ground vehicles from an aircraft using a microwave radar with high range resolution. An MTE X-band radar data collection with moving vehicles occurred at China Lake, CA, in September 1995. The (ERIM DCS) airborne radar used in this collection is a 600 MHz instantaneous bandwidth, linear FM system with two along-track antennas to enable clutter cancellation, an obvious requirement for boosting the contrast of slow movers in competing ground clutter. The nominal data collection mode was synthetic aperture radar (SAR) with simultaneous receive beams as well as alternating transmit pulses from each aperture. Stationary clutter could be imaged with 0.3-m resolution in both range and cross-range.

This paper discusses a method for adaptively canceling clutter by using SAR clutter data from each of the simultaneous receive beams. One SAR image is equalized to the other by amplitude and phase compensation both in range and in cross-range (Doppler). Then, the images are subtracted for clutter cancellation. Vehicles moving with respect to the clutter are then easily detected and passed to a high-resolution classifier, which is outside the scope of this paper.

This paper concentrates on the shapes of the amplitude and phase compensation curves, their physical causes (such as post-deramping amplifier mismatches, range and cross-range distance between antenna horns, and antenna boresight error), the day-to-day and pass-to-pass variations that were encountered, and the estimation and clutter cancellation accuracy.