Angle-of-Arrival Estimation of Microwave Signals Based on Optical Phase Scanning

A photonic method to estimate the angle-of-arrival (AOA) of microwave signals based on optical phase scanning is proposed and experimentally demonstrated. At remote antenna unit (RAU), one received high-frequency microwave signal is directly applied to a phase modulator (PM), and another received high-frequency microwave signal coupled with a low-frequency large-voltage sawtooth-wave signal is applied to another PM. The sawtooth-wave signal is used to scan the phase of the optical sideband from 0 to 2π. After transmission over a segment of fiber link, the AOA parameter can be estimated by processing the obtained low-frequency electrical signals at central office (CO). Such scheme can be applicable to either single-tone or wideband microwave signals. Experimental results show that the AOA measurement errors are less than 2.27° and 4.45° for a single-tone signal at 10 GHz and a 2-GHz broadband signal with the center frequency of 18 GHz, respectively.