A Microwave Photonic FMCW Radar With Suppressed Phase Noise Based on Equal Phase Interval Sampling

Microwave photonic (MWP) frequency-modulated continuous-wave (FMCW) radars break through the bandwidth limitations of electronic radar by photonic frequency multiplication and mixing. However, it induces additional phase noise to the radar signal, which is undesirable for radar target detection and recognition. To deal with this issue, this paper presents and experimentally demonstrates a MWP FMCW radar with suppressed phase noise by equal phase interval sampling. The radar signal, of which the bandwidth is broadened by MWP frequency multiplier, is split into two paths. One path is delayed by optical fiber as a reference signal, and the other path is transmitted to free space and reflected by the target as an echo signal. The reference signal and the echo signal are de-chirped by mixing with the radar signal at an MWP mixer. The de-chirped reference signal is sampled with equal phase interval and the corresponding time are recorded, at which the de-chirped echo signal is sampled. The de-chirped echo signal with suppressed phase noise can be obtained by rearranging the re-sampled de-chirped echo signal with equal time interval. In the experiment, the validity of the proposed system is demonstrated.