Compact photonic-assisted angle-of-arrival measurement system eliminating direction ambiguity and power dependence

A compact photonic-assisted angle-of-arrival (AOA) measurement system is proposed and experimentally demonstrated, effectively eliminating direction ambiguity and mitigating dependence on the power of the microwave signal under test. Unlike traditional methods that set the antenna spacing to be half the wavelength of the microwave signal under test, this work introduces, to the best of our knowledge, a novel configuration with an antenna spacing of one-quarter wavelength, along with a 90° phase shift in one signal path. It allows the phase difference between the two modulation signals to vary from 0° to 180° as the AOA changes from -90^∘ to 90°, facilitating clear measurement of the phase difference and eliminating direction ambiguity. The system employs a polarization-division multiplexing Mach-Zehnder modulator to generate modulated signals with orthogonal polarization states, set at a 45° principal angle relative to a subsequent polarization beam splitter. Two complementary phase-to-power mapping curves are generated, and a simple difference-to-sum calculation is used to eliminate the influence of microwave signal power. Simulations investigate the impact of key parameters such as modulation depth, modulator extinction ratio, and principal angle on measurement accuracy. Experimental results confirm the effectiveness of the proposed system, demonstrating precise AOA measurements over a broad frequency range and varying power levels, with a measurement range extending to ±63^∘.