Rainbow Beams for Wideband mmWave Radar: Beam Training

We present a novel fast beam training method for fast moving targets in millimeter wave (mmWave) wideband radar systems. True-time-delayers (TTDs) are utilized to generate frequency-dependent radar rainbow beams using one orthogonal frequency-division multiplexing (OFDM) symbol, simultaneously covering targets located in the entire angular space for fast beam training. We first propose a scheme based on a single-antenna radar receiver. It can effectively detect and estimate different parameters of interest of targets, including their angles, distance related delays, and velocity related Doppler frequencies, but faces a Doppler ambiguity challenge. To tackle this limitation, we further introduce a scheme based on a multi-antenna receiver, which provides high-precision estimation performance. Simulation results reveal the effectiveness of the proposed rainbow beam-based training method for detecting and estimating mobile targets.