Generation of frequency septupled chirped microwave waveforms with increased TBWP based on two cascaded polarization modulators

In this paper, we have proposed a chirped microwave waveform generation scheme with septupled carrier frequency and increased time-bandwidth product (TBWP) by using two cascaded optical polarization modulators (PolMs) and an interleaver (IL). In the scheme, the first PolM is driven by a radio frequency (RF) signal followed by an IL to generate orthogonally-polarized +3rd and −4th-order sidebands. Then the other PolM driven by a parabolic signal is used to introduce the parabolic phase difference between the two tones. Subsequently, a photodiode (PD) with an optical polarizer is used to beat the two orthogonally-polarized optical tones for generating the frequency septupled chirped microwave signal. In order to increase the TBWP, the parabolic signal is segmented into multi-pieces to increase the bandwidth of the generated signal; and phase encoding or stretching the parabolic signal is used to increase the temporal duration. Simulation results show that chirped microwave waveform with the carrier frequency of 70 GHz, bandwidth of 29.49 GHz, TBWP of 19859.40 is generated by dealing with the electrical parabolic driving signal, which matches well with the theoretical analysis. The generated linearly chirped signals with high-frequency and large-TBWP is expected to the range resolution and detection range when used in radar system.