Photonic Approach for Unambiguous Measurement of AOA and DFS With Self-Interference Cancellation

We propose a compact photonic system based on a dual-polarization dual-drive Mach–Zehnder modulator (DP-DDMZM) to measure Doppler-frequency-shift (DFS) and angle-of-arrival (AOA). Compared to previous research, the key innovation of our system is that the self-interference signals can be eliminated while maintaining excellent measurement performance. The sub-DDMZMs are driven by the echo signals and the reference signals and two intermediate frequency (IF) signals are generated after photoelectric detection from the orthogonal polarization channels. By measuring the frequency of the IF signals, the DFS with direction identification can be calculated. The unambiguous AOA measurement can be acquired by recording the phase difference between the output IF signals from the two channels. The self-interference signals are directly cancelled by matching the power and inversing the phase with the transmitted signals. The experiment results show that the cancellation depth of the self-interference signals is around 35 dB. The DFS measurement errors are within 0.2Hz and the errors of the −70.8° to 70.8° AOA measurement are less than 2.2°. The system can be applied to miniaturized airborne/vehicular radars, full duplex detection radars, and multiple input multiple output (MIMO) radar arrays. © 2023 Optica Publishing Group