Refined method for terrain scattered interference mitigation

Abstract

Terrain scattered interference mitigation methods for airborne radar have been described in previous papers and deconvolution methods for interference suppression have been proposed. This paper describes a refined method for terrain scattered interference mitigation and investigates performance for different conditions and limitations. An important part of the method is a threshold function to enable least squares estimation of the multipath impulse response. Least squares estimation can be applied if the impulse response is time limited or if a limited number of impulse response coefficients are required for sufficient interference suppression. The impulse response estimation can be performed either before or within the coherent processing interval. It is assumed that the direct path signal can be accurately estimated without strong multipath errors. Small relative Doppler shift errors are required between the direct path and the terrain scattered paths. Several strong jamming signal sources cannot be resolved and suppressed. Receiver blocking gives errors in the impulse response estimate and jamming signal residues in the main beam signal. Clutter signals might have to be suppressed to get accurate impulse response estimates. Bandwidth effects must be considered to get numerical stability in the inverse filtering and deconvolution operations. The refined method can suppress interference down to the receiver noise level in simple terrain scattering scenarios.