A novel approach for photonic generation of tunable linearly chirped microwave waveform with large time-bandwidth product

We present a novel photonic approach based on heterodyne between a multiple-dispersed optical pulse and a continuous optical signal to generate tunable linearly chirped microwave waveform (LCMW) with large time-bandwidth product (TBWP). The carrier frequency of the generated waveform can be changed by tuning the frequency of continuous optical wave outputted from the tunable laser source (TLS),while the TBWP of the LCMW can be changed by optically pumping the linearly chirped fiber Bragg grating (LCFBG) in the dispersive loop with different pumping powers. An extremely large equivalent dispersion will be obtained because of the dispersive loop used in the system, which leads to the generation of LCMW with long temporal duration. The capability of the presented method is verified via numeric simulation.