Fitting derivative autofocus for stepped frequency radar

High range resolution (HRR) profiles can be obtained using stepped frequency waveforms. A burst of linearly frequency modulated pulses on different carrier frequencies are transmitted and a suitable signal processing combines the returned echoes from each pulse to obtain a wide synthetic bandwidth. Target motion during stepped frequency processing causes several degradation effects, which inevitably reduce the desirable range resolution. This paper describes an autofocus technique that can be employed to compensate motion degradation effects on HRR profiles. The algorithm is based on a function of the derivative of the range profile as a measure of range profile focus. As an application the estimation accuracy of target to radar radial speed is tested in case of both one and two reflectors at different SNR (signal to noise ratio) using Monte Carlo simulation. The performances, in terms of standard deviation of radial velocity estimation of the proposed algorithm have been compared with that obtained with the contrast technique.