Advanced Waveform Processing

Radar pulse compression waveforms can be processed with the waveform's "matched filter" to provide the optimum detection performance of a target in the presence of white Gaussian noise. Unfortunately, these optimally processed waveforms also exhibit undesired spurious responses called time (or range) sidelobes, which can significantly degrade the detection of small radar targets in the vicinity of large returns. This SBIR considers a general technique for suppressing the time sidelobes of any waveform (LFM, m-sequence, chaotic, etc.) with a minimum loss in sensitivity and resolution. The method uses a constrained optimization algorithm to compute the filter response function that provides the maximum output SNR subject to constraints on the allowed levels of the time sidelobes. As an example, the type of sidelobe suppression achievable with a 63-bit m-sequence code reduces sidelobes from -21 dB to -40 dB with a small SNR loss of only 1.2 dB, as compared to the matched filter. An additional benefit of this approach is that the sidelobe control is very flexible. It need not be symmetric about the main response, and it can include deeper notches in regions of special interest. Moreover, for certain processor implementations the increased capability is achieved with no additional real-time processing requirements.