Dual-band dechirping LFMCW radar receiver with high image rejection using microwave photonic I/Q mixer

In this paper, a photonics-based dual-band linear frequency-modulated continuous wave (LFMCW) radar receiver is proposed. The system core is a microwave photonic in-phase and quadrature (I/Q) mixer, whose inherent large bandwidth, high I/Q balance and favorable uniformity enable the receiver to operate over an extremely wide frequency range. An integrated dual-band waveform offers the possibility of independent detection, allowing the sharing of hardware resources and joint dechirp processing of dual bands. In the proof-of-concept experiment, the distance measurements of S- and C-bands are implemented, with a high and uniform image rejection exceeding 28 and 30 dB, respectively. The image rejections of the two bands can be further improved to 43 and 41 dB at least by digital signal processing (DSP). The proposed photonic-assisted receiver is thus able to simplify the architecture and improve performance for the multispectral sensing application.