Doppler-Robust Complementary-on-Receive Radar Processing

Reduction of sidelobe energy in the form of complementary cancellation was a property first exploited by the summation of co-designed phase code autocorrelations. These codes are subject to distortion from the radar transmitter, limiting their practical application. The sidelobe cancellation itself degrades when the codes are subject to Doppler shifts. Mismatched complementary-on-receive filtering (MiCRFt) was the first technique to move the complementary cancellation condition to the receive side of the radar problem such that the use of complementary-agnostic waveforms is permissible. MiCRFt leverages a diverse set of unique waveforms and joint design of least-squares mismatched filter (LS-MMF) subsets, where the sum of their cross-correlations significantly reduces range sidelobes. However, the degree of sidelobe reduction achieved by standard MiCRFt is Doppler shift dependent, with subsequent degradation of sidelobe reduction for increasing Doppler shifts, motivating a Doppler-robustness extension.

In this thesis, a Doppler-generalized version of MiCRFt, dubbed DG-MiCRFt, is presented and demonstrated in simulation and both loopback and open-air experimentation. Derivation of DG-MiCRFt filters involves a sinc-taper scaling of the original MiCRFt desired response, relating to covariance matrix tapers (CMTs). This extension is capable of inducing complementary sidelobe cancellation over a user-defined span across slow-time for little extra computational cost. Increasing the width of the complementary span is shown to act as a trade-off for cancellation floor depth versus the degree of mismatch loss. DG-MiCRFt is shown to be capable of mitigating range sidelobe modulation for high-powered scattering with non-zero Doppler shifts within the complementary span, assessed via artificial Doppler shift of open-air direct-path scattering.