Dual-chirp waveform generation and its TBWP improvement based on polarization modulation and phase coding

Abstract

A photonics approach to generate a phase-coded dual-chirp waveform with reconfigurable time duration, arbitrary large TBWP, flexible tuning frequency and bandwidth is proposed and demonstrated. In the scheme, one polarization modulator (PolM) is applied to modulate a repetitive parabolic waveform with an dual-wavelength optical signal, while another PolM is utilized to achieve phase coding with a Pseudorandom (PN) sequence. After balanced detection, a phase-coded dual-chirp signal with improved time-bandwidth product (TBWP) can be generated. The approach is verified by simulation. Basis dual-chirp waveforms with tunable central frequency of 20 to 30 GHz, tunable bandwidth of 1.25 to 5 GHz but fixed TBWP of 16 are generated. Then, 30-GHz central frequency, 2.5-GHz bandwidth phase-coded dual-chirp signals with phase shift of π, TBWP of 240, 1008 and 2032 are obtained. The generated dual-chirp microwave waveform can be used in a radar system to improve its range-Doppler resolution.