Photonic approach to linearly chirped microwave waveform generation with large time–bandwidth product capability

Photonic approach to generating linearly chirped waveforms with large time–bandwidth product (TBWP) is proposed and demonstrated. In the approach, a dual-output dual-parallel Mach–Zehnder modulator (DPMZM) is employed to generate dual-tone wavelengths in the two output ports. The polarization modulator (PolM) is employed to conduct complementary phase modulation of the dual-tone wavelengths. After driving PolM with parabolic signal, frequency-doubled chirped microwave waveform will be obtained from photodetector (PD). To enlarge the TBWP, parabolic waveform is split into time domain and convolved with binary sequences to increase the bandwidth and temporal duration of the generated signal simultaneously. Simulation results show that linearly chirped microwave waveforms with carrier frequency of 40 GHz, bandwidth of 12.5 GHz, time duration of 819.2 ns are generated. After splitting and code-convolving with binary sequence, TBWP of the generated signal is enlarged to 10,240. Pulse compression performances of the generated signal are analyzed, and structure stability is also investigated.