Reconfigurable Radar Waveform Generation Based on Selective Modulation of Optical Frequency Comb Lines

Abstract

Linear frequency modulation (LFM) and phase-coded modulation (PCM) signals, including intra-pulse LFM and inter-pulse PCM signals, are widely applied in the radar system. Here, we numerically demonstrate the reconfigurable radar signal generation based on an optical frequency comb (OFC) via selective modulation of the comb lines. The OFC line modulator consists of a 1 × 2 optical splitter, two tunable optical bandpass filters, two phase modulators (PMs), and a 2×1 optical multiplexer. Two selected OFC lines are injected into the two PMs and modulated by specific microwave signals. The output optical signals are combined and sent to a photodetector to perform the optical-to-electrical conversion. The carrier frequency of the generated signal is determined by the frequency interval of the selected OFC lines. By tuning the optical bandpass filters to select different OFC lines, the carrier frequency of the generated signal can be tuned. The waveform of the generated signal depends on the modulation signal. When a coding signal is applied to one of the PMs, a PCM signal can be generated. Similarly, when a parabolic signal serves as the modulation signal, an LFM signal can be obtained. Furthermore, the hybrid waveforms with intra-pulse LFM and inter-pulse PCM can be generated by applying the coding signal and the parabolic signal to the two PMs, respectively. Thanks to the selective modulation of the OFC lines, a low-frequency electrical waveform generator is sufficient to produce high-frequency radar waveforms.