Multiband phase-coded chirp microwave pulse generation for improving range-Doppler resolution

A photonic approach for generating pulsed phase-coded chirp microwave waveforms is proposed. The main component of the system is a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM). Two same linearly chirped signals andtwo differential electrical 13-bit Barker coding signals are applied to the DP-DDMZM. By adjusting the voltage biases of the modulator, multiband pulsed phase-coded chirp signals with multiplied center frequencies and bandwidths can be generated. To the best of our knowledge, the main novelty of the work is that, by phase coding the linearly chirped signal, waveforms with thumbtack-like ambiguity function can be achieved, which improve the range-Doppler resolution. Additionally, a compact and stable structure is realized since only one modulator is employed. The generated microwave waveforms can be used to implement the communicating and sensing simultaneously. The multiband phase-coded chirp signals with fundamental, double, triple, and quadruple center frequencies are obtained. In addition, pseudo-random (PN) sequences with longer bit length are further examined to demonstrate the improvement of ambiguity functions and -3dB contour maps. The approach is well theoretically analyzed and numerically verified.