Spectral Cohabitation and Interference Mitigation via Physical Radar Emissions

Auctioning of frequency bands to support growing demand for high bandwidth 5G communications is driving research into spectral cohabitation strategies for next generation radar systems. The loss of radio frequency (RF) spectrum once designated for radar operation is forcing radar systems to either learn how to coexist in these frequency spectrum bands, without causing mutual interference, or move to other bands of the spectrum, the latter being the more undesirable choice. Two methods of spectral cohabitation are proposed and presented in this work, each taking advantage of recent developments in random FM (RFM) waveforms, which have the advantage of never repeating. RFM waveforms are optimized to have favorable radar waveform properties while also readily incorporating agile spectral notches. The first method of spectral cohabitation uses these spectral notches to avoid narrow-band RF interference (RFI) in the form of other spectrum users residing in the same band as the radar system, allowing both to operate while minimizing mutual interference. The second method of spectral cohabitation uses spectral notches, along with an optimization procedure, to embed a communications signal into a dual-purpose radar/communications emission, allowing one waveform to serve both functions simultaneously. Preliminary simulation and open-air experimental results are shown which attest to the efficacy of these two methods of spectral cohabitation. Improvements are proposed to extend the capabilities of each method such that they can provide further utility to both radar and communications functions while minimizing any mutually included performance degradation.