Multi-Functional Radar Waveform Generation Based on Optical Frequency-Time Stitching Method

A photonic-assisted multi-functional radar waveform generator for single-chirped, counter-chirped, and dual-band linear frequency-modulated (LFM) microwave waveforms generation is proposed and experimentally demonstrated based on an optical frequency-stepped waveform (FSW) generator. The optical FSW generator is realized by an optical switch and an optical frequency shifting loop (OFSL). When an electrical rectangular LFM pulse is applied to the proposed signal generator, an optical frequency-stepped LFM signal would be generated. By carefully setting the time length and the bandwidth of the rectangular LFM pulse, we can achieve an optical linearly-chirped continuous wave. Optical frequency-time stitching is thus realized. Combining the optical linear-chirped signal with one or more optical wavelengths, and meticulously adjusting the value of the optical wavelengths, single-chirped, counter-chirped or dual-band LFM signals can be produced. An experiment is carried out. Single-chirped and counter-chirped LFM signals of 8-32 GHz over a time duration of 5 μs, and dual-band LFM signals of 8-16 GHz & 15-23 GHz and 8-20 GHz & 20-32 GHz are generated. The ambiguity functions of the generated signals are investigated.