We consider an incumbent radar system which coexists with an OFDM communication system. A method for detecting the presence of an incumbent radar (chirp) signal is proposed assuming the radar and communication systems do not coordinate spectrum access or share system or signal parameters. The detection strategy for the OFDM system relies on adaptive beamforming, and searches for anomalies in residual errors across subcarriers and OFDM symbols. It does not require channel state information or knowledge of radar waveform parameters. We first apply the method to fully digital arrays, then extend it to hybrid True Time Delay arrays for wideband beamforming. Simulation results show the effectiveness of the proposed detection algorithm in achieving a low probability of misdetection for both types of arrays under various scenarios.
