Multiband microwave photonic radar with increased target detection ability

We propose and demonstrate a novel, to the best of our knowledge, multiband microwave photonic radar, with increased target detection ability. An optical frequency shifting loop (OFSL) is employed in which a pulsed optical carrier modulated by a linearly frequency-modulated (LFM) waveform is recirculating in the loop to generate a series of optical waveforms with increased central frequencies and bandwidths. By beating the optical waveforms at the output of the OFSL with the optical carrier, a multiband LFM microwave waveform is generated, which is transmitted to free space via an antenna. At the same time, a portion of the multiband microwave waveform is sent to the radar receiver as a reference waveform. At the radar receiver, the multiband microwave waveform reflected by a target is received, which is de-chirped by mixing it with the reference waveform. Experimental verification of a radar system consisting of three-band (C-band, X-band, and Ku-band) LFM waveforms with instantaneous bandwidths of 1, 2, and 3 GHz, respectively, is performed. The range resolutions for the three bands are measured to be 15.98, 8.39, and 5.64 cm, respectively. By leveraging different frequency bands, the multiband radar can mitigate the limitations of single-band radars, such as material absorption and resolution constraints, to provide optimal performance in terms of detection range, range resolution, and detectability.