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FOURTH ANNUAL
ASAP '96 WORKSHOP

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Hot Clutter Cancellation
with Orthogonal
Beamspace Transforms

Stephen M. Kogon, Douglas B. Williams, and E. Jeff Holder
Georgia Institute of Technology
777 Atlantic Drive
Digital Signal Processing Laboratory
Atlanta, GA 30332-0250
tel: (404) 854-9832
fax: (404) 894-8363
email: kogon@ee.gatech.edu
email: dbw@eedsp.gatech.edu

Abstract Hot clutter refers to terrain-reflected jammer interference that is incident on the radar array from many azimuth angles and, therefore, distributed throughout the mainbeam. Cancellation methods seek to use interference energy present in other portions of the angular spectrum to remove the mainbeam interference. The conventional adaptive canceller makes use of a single reference beam with sufficient temporal taps to cover the range extent of the hot clutter signal, typically quite large. In this case, all the degrees of freedom have been devoted to temporal adaptivity. However, the hot clutter energy is not limited to the mainbeam and is usually found throughout the angular spectrum. Independent temporally delayed replicas of the interference are present at many different azimuth angles. We propose a hot clutter cancellation method, implemented using a generalized sidelobe canceller structure, that makes use of the entire angular spectrum through an orthogonal beamspace transformation. The temporal window of the resulting canceller is greatly reduced, far below the range extent of the hot clutter, thereby trading off spatial for temporal degrees of freedom. The performance of the full beamspace hot clutter canceller is demonstrated on data collected in the Mountaintop experiment where it is shown to achieve superior performance relative to the single auxiliary beam canceller for the same number of degrees of freedom. Alternatively, cancellation to an acceptable interference level is achieved with a reduction in total degrees of freedom by using all of the spatial information available.

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