Photonic system for Doppler-frequency-shift and Angle-of-arrival simultaneous measurement using dual-parallel Mach-Zehnder modulator

A simple photonic system is proposed to measure the Doppler frequency shift (DFS) and Angle of arrival (AOA) of microwave signals simultaneously. The echo signals received by the two antennas are fed into two sub-MZM of a dual-parallel Mach-Zehnder modulator (DPMZM) respectively, and the reference signals are sent into one of the sub-MZM. The introduction of reference signals makes it easier to determine the direction of DFS. After the reference signal and echo signal pass through the low-speed PD, the beating signal is obtained. The value and direction of the DFS can be derived from the frequency of the down-converted signal. And the measurement of AOA can be calculated from the power of the output signal. The experimental results show that the echo signal measurement errors of DFS are less than +/- 0.5 Hz in the operating frequency range of 20 GHz, and the power sensitivity is less than-40 dBm. AOA has measurement errors of less than +/- 1.5 degrees in the range of 0 to 90 degrees. In addition, by adding only one test branch, the system can achieve the unambiguous measurement of AOA in the range of +/- 90 degrees.