A Costas-Based Waveform for Local Range-Doppler Sidelobe Level Reduction

Target masking due to high sidelobes in the range-Doppler domain is a common problem in radar signal processing. Masking occurs when there is large variation in targets' signal-to-noise-ratio levels, caused by differences in either range or radar cross section. In this letter, we consider the design of a waveform to reduce the masking of far range targets caused by near range targets. Our method is based on a time-frequency concatenation of a Costas sequence with shifted parts of itself. It allows the user to design a low sidelobe region in the range-Doppler domain. Moreover, it approximately preserves the desirable uniform sidelobe level and thumbtack behavior of the Costas ambiguity function. We demonstrate a 20 dB sidelobe level reduction within the desired region compared to a normal Costas code with the same bandwidth and pulse length.