Expanding the Doppler Span of Fast-Time Sidelobe Suppression for Random FM Waveforms

Numerous random FM (RFM) waveform design techniques have been developed and shown to provide good spectral containment and low autocorrelation sidelobes, as compared to unoptimized RFM waveforms whose autocorrelation sidelobes depend on time-bandwidth (TB) product alone. However, these design approaches typically do not account for sidelobes as a function of fast-time Doppler. To address this, the Pseudo-Random Optimized FM (PRO-FM) design approach is augmented with an additional projection stage. This new optimization called Doppler-Expanded Sidelobe Suppression Pseudo-Random Optimized (DESSPRO) is designed to meaningfully expand the region of sidelobe suppression in fast-time Doppler.

To do so, the DESSPRO algorithm is defined, derived, and explored thoroughly according to its various parameters, while also considering different implementations from a computational efficiency standpoint. Several test cases are considered and demonstrated in both simulation and over the air experiments. These experiments show the ability of DESSPRO waveforms to maintain the desirable spectral containment and constant amplitude properties of PRO-FM, while substantially reducing the problematic range-Doppler sidelobes of the ambiguity function, which are otherwise ubiquitous across both unoptimized and optimized RFM implementations.