Photonic Approach to Multi-band Dual-chirp Microwave Waveform Generation with Quadruple Bandwidth

Abstract

We propose a scheme for generating a microwave waveform with dual-band, dual-chirp, linearly chirped characteristics and quadruple chirp bandwidth. In this scheme, we employ two cascaded Mach-Zehnder modulators (MZMs), with each modulated by a microwave signal and a linearly frequency modulated (LFM) signal. This modulation technique extends the LFM signal to multiple frequency bands and enhances its bandwidth. By properly adjusting the microwave signal's frequency and the LFM's carrier frequency, we can intelligently combine the up-chirp and down-chirp signals obtained after heterodyne beating in the photodetector (PD). This combination results in the creation of multi-band dual-chirp signals with quadruple chirp bandwidth. Our simulation demonstrates the simultaneous generation of dual-chirp microwave waveforms in the X, Ka, U, and V bands, with central frequency-bandwidth ranges of 10GHz-4GHz, 30GHz-4GHz, 50GHz-4GHz, and 70GHz-4GHz respectively. These dual-chirp signals possess a bandwidth four times that of the driving chirp signal, leading to a Time Bandwidth Product (TBWP) four times greater than that of the driving chirp signal. Consequently, the proposed scheme has the potential to significantly improve range Doppler resolution in modern radar systems. Additionally, the high-frequency and large-bandwidth dual-band dual-chirp LFM signals generated by this approach are anticipated to enhance range resolution and detection range in multitarget radar systems.