Photonic Frequency Down Conversion Approach to Measure Microwave Signal Angle of Arrival

This paper presents an angle-of-arrival (AOA) measurement system based on microwave photonic frequency down conversion. It has the novelty of no LO is needed for conversion process. Instead, a ramp waveform used to shift optical carrier, which phase modulated by signal in subsequent stage. Two low-frequency IF signals are generated after photodetection. The AOA incoming can be determined measuring difference two signals. Comparing with previously reported converter systems, proposed structure does not need high-frequency tunable source and electrical components. Expensive bulky equipment such as spectrum analyser required system. Experimental results show different-frequency different-power signals, small errors.