Optimized-Slope FMCW Waveform for Automotive Radars

Vast deployment of Frequency Modulated Continuous Wave (FMCW) radars in multiple passenger and commercial vehicles has led to a significant vehicle-to-vehicle radar interference. The interference in all of these cases is largely due to simultaneous use of shared spectrum when operating in the detection range of the other sensors and the inherent lack of coordination between radars resulting from the lack of a centralized control and resource allocation mechanism. In classical FMCW waveforms this problem has been solved by using multiple chirp signals with different slopes. But the way of selecting slopes for different chirps may not be optimal and introduces long measurement time and high ISL value for the range-Doppler map. In this paper, we propose an optimization framework based on Majorization-Minimization (MM) frame-work to design multiple chirp waveforms with different slopes that provide small ISL values in its range-Doppler map. To this end, we formulate the optimization problem based on designing a waveform with quadratic phase segments. Every segment will be synthesized as a chirp after the optimal solution was obtained. Consequently the new waveform makes the FMCW radar system less susceptible to interference, while it leads to an optimal ISL. The novel waveform offers better immunity to interference and is implementable using the dechirp technique which makes it a cost efficient solution for automotive sensing and other Commercial Off-The-Shelf (COTS) applications.