Photonic-Assisted Wideband Frequency Down-Converter With Leakage Cancellation and Image Rejection for FMCW Radar Receiver

Frequency modulated continuous wave (FMCW) radars with de-chirping receivers can achieve high resolution and real-time microwave imaging. However, the inherent leakage interference from transmitter to receiver and image interference from image frequencies will degrade sensitivity and dynamic range of the receiving system. In this paper, a novel photonic-assisted down-converter based on a dual-polarization binary phase-shift keying (DP-BPSK) modulator, which can achieve leakage cancellation and image rejection concurrently for wideband linear frequency modulated (LFM) signals, is proposed and demonstrated. Both theoretical analysis and simulation verification are performed. Considering this scheme in the application of a radar receiver, the leakage signal, signal of interest, and image signal are emulated as wideband LFM signals with 2GHz bandwidth centered at 20, 21, 19GHz. The simulation results show an excellent leakage cancellation depth and image rejection depth of 54dB and 53.5dB respectively. The proposed scheme can be applied in an FMCW radar receiver so as to optimize the detection performance.