The effects of Doppler and pulse eclipsing on sidelobe reduction techniques

Radar sidelobe reduction techniques based on deconvolution generally rely on an accurate estimate of the system point spread function (PSF). Targets traveling at nonzero velocity induce a Doppler shift and have an altered PSF, which reduces sidelobe reduction performance. Also, in situations where a target is close to the radar, pulse eclipsing occurs- reflected energy arrives at the receiver while it is switched off during transmission. Eclipsing has the effect of a range-varying PSF, which also reduces sidelobe reduction performance. This paper describes a method to account for both Doppler and pulse eclipsing using the thresholded minimum mean square error (MMSE-T) sidelobe reduction algorithm. A new procedure for estimating noise power, which is required by the algorithm, is presented. Simulation results show the modified algorithm is able to reduce sidelobes such that a weak target obscured by the sidelobes of a 40 dB stronger target is clearly revealed, assuming the weak target would be detectable alone. These results hold when the true target velocities are not known as long as a reasonable estimate is obtained through tracking or Doppler processing of the strongest targets. A qualitative comparison of MMSE-T with the iterative re-weighted least squares (IRLS) algorithm shows it to be the better of the two.