TIME VARYING ADAPTIVE CLUTTER FILTER AND CLUTTER RESIDUE SENSOR

Clutter reduction is accomplished by dividing the sampling times of received radar signals into blocks containing a plurality of sampling times. The average clutter value in each block is estimated by averaging the signal returns for the sampling times in the block. Block average clutter values are time positioned at a selected sampling time position in a block and a smooth function with continuous first and second derivatives is passed through the average clutter value points. In a preferred embodiment the smooth function is a cubic spline comprising third order polynomial segments between average clutter value points. Clutter values at the sampling points are extracted from the smooth function and respectively subtracted from the received radar signals. A clutter sensor examines the resulting radar signals for clutter distortion and eliminates radar signals that are not substantially clutter free.