Real-Time Photonic Radar With Multi-Band Agility Based on Mode Locked Laser

A photonic radar with real-time detection ability and multi-band agility is proposed and demonstrated. In the proposed scheme, a dual-polarization Mach-Zehnder modulator (DP-MZM) coupled by an optical pulse from mode locked laser (MLL) is used to implement baseband signal sampling and echo signal receiving in orthogonal polarization, independently. After extracting the baseband signal under optical sampling from partial output signal of DP-MZM, it is transformed to microwave signal, in which, by choosing specific harmonic mixing signal with bandpass filter at electronic transmitter, the up-conversion radar transmitting signal in expected band is obtained. Meanwhile, another partial of optical signal from DP-MZM is polarization demultiplexed to the optical reference signal and receiving signal by a polarization beam splitter. Then, the de-chirping of radar echo signal can be completed with a balanced photodetector for balanced detection the optical reference signal and receiving signal. By conducting the proof-of-concept experiments, the feasibility of the proposed system is verified in K-band with a range resolution 2.22 cm. Furthermore, the multi-band agility of radar can be realized with adjusting the passband of radar electronic transmitter.