Wideband Frequency and Angle-of-Arrival Measurement System Based on Optical Subsampling

We proposed a system that simultaneously supports measuring the frequency and the angle of arrival (AOA) of the radio frequency (RF) signal. In the proposed system, the RF signals from different antennas are loaded on different arms of a dual-polarization Mach-Zehnder modulator (Dpol-MZM) and are subsampled by dual optical combs, respectively. The frequency of the receiving RF signal can be obtained from two intermediate frequencies (IF), and AOA can be obtained from the phase difference between the upper- and lower-channel IF signals. In the experiment, 0.5–40 GHz frequency measurement range with an error of ±0.06 MHz and ±180 phase shift measurement range with an error of 1.8 can be achieved based on a low-frequency electronic analog-to-digital converter (ADC). The processing of both broadband signal and multitone signal and the system stability are also verified.