Photonic-Assisted Generation of Flexible and Switchable Multi-Band Linearly Frequency Modulated Microwave Waveforms

A novel photonic scheme based on parallel dual-drive Mach-Zehnder modulator (DDMZM) to generate flexible and switchable multi-band linearly frequency modulated (LFM) microwave waveforms is proposed. In the scheme, a radio frequency (RF) local oscillator is applied to one arm of DDMZM1 and DDMZM2 with a relative phase of 90°, respectively; while a single-chirp signal to the other arms of the two DDMZMs with a tunable relative phase shift. The generated two independently lightwaves are detected by a balanced photodetector (BPD) and the switchable multi-band LFM signals are generated flexibly. By appropriately adjusting the phase difference θ, dual-band complementary LFM signals and multi-band LFM signals can be easily switched. Based on simulations, the dual-band complementary LFM waveforms centered at 10 GHz and 30 GHz are generated with a doubled bandwidth (3.2 GHz) as θ = 0, the multi-band LFM microwave waveforms with center frequency-bandwidth of 10 GHz-1.6 GHz, 20 GHz-6.4 GHz and 30 GHz-1.6 GHz, covering X, K and Ka bands, are simultaneously obtained with flatness of 1.9 dB as θ = π/2 or 3π/2. Their autocorrelation results manifest high peak-to-sidelobe ratio (PSR) about 14 dB, and good pulse compression capabilities. The presented scheme features its compact structure, easiness in switching control, as well as larger bandwidth, and has potential applications in multifunctional radars.