Photonics joint radar and communication system using dual-band LFM-based signals with opposite chirp polarities

A photonics joint radar and communication (JRC) system using dual-band linear frequency modulation (LFM)-based waveforms is proposed and demonstrated. In the scheme, four optical chirp sidebands are generated and divided into two branches to achieve two LFM signals with different frequencies and opposite chirp polarities. In each branch, a dual-output modulator is used to perform amplitude modulation (AM) or phase modulation (PM) for the generated LFM signal. The dual-band AM-LFM or PM-LFM signals are used for JRC purpose. The dual-band radar echoes are frequency down-converted and de-chirp processed to obtain distance and velocity parameters. For communication, the AM-LFM signals are envelope demodulated while the PM-LFM signals are coherent demodulated. The approach is verified and the performance tradeoff between radar and communication is discussed. A 19–15 GHz down-chirp AM-LFM signal with rate of 0.1 Gb/s and a 33–37 GHz up-chirp one with rate of 1 Gb/s are generated by using an up-chirp 3.5–5.5 GHz LFM signal. Both distance and velocity parameters can be obtained and the detection accuracy can be guaranteed by using the generated AM-LFM signals, but the radar maximum detection distance will be compromised due to the AM operation. Furthermore, a 10-Mb/s rate 19–15 GHz down-chirp and a 0.1-Gb/s rate 33–37 GHz up-chirp PM-LFM signals are generated. The radar maximum detection range can be guaranteed by using the PM-LFM signals, but the detection accuracy will be deteriorated due to the PM operation.