Angle-of-arrival estimation of a microwave signal based on optical interference and stimulated Brillouin scattering

We propose an optical approach to estimate the angle of arrival (AoA) of a microwave signal. The microwave signal and its phase-shifted replica received from separated antenna elements are applied to a null-biased dual-drive Mach–Zehnder modulator. An optical loss resonance at the optical carrier is introduced by stimulated Brillouin scattering in optical fiber. By measuring the resultant optical power, we can obtain the phase difference, from which the AoA of the incoming microwave signal can be determined. An experiment is carried out, which exhibits that phase measurement errors are <1.86 deg with a phase difference from 9 deg to 162 deg.