Concurrent photonic measurement of angle-of-arrival and chirp rate of microwave LFM signal

A photonic approach to concurrently measure the angle-of-arrival (AOA) and the chirp rate of a linear frequency modulated (LFM) signal is proposed and experimentally demonstrated. The measurement is achieved by estimating the differential frequency of a two-tone signal output by a dual-parallel Mach–Zehnder modulator and an additional asymmetry Mach–Zehnder interferometer. Experiments show that the AOA and the chirp rate are measured simultaneously, with an AOA measurement error of ±0.1° at an signal-to-noise ratio (SNR) of 9.6 dB. When the SNR is -10.4 dB, the AOA error is ±1.3°, and the chirp rate, measured as 210.2±1.5 Hz/ps, has a standard deviation of 0.7%. The measured chirp rate agrees well with the real LFM signal.