Photonics-Based Reconfigurable Time–Frequency Analysis and Angle-of-Arrival Measurement System

A photonics-based system for simultaneous time–frequency analysis and angle-of-arrival (AOA) measurement with reconfigurable frequency resolution has been introduced and experimentally demonstrated. Simultaneous AOA-to-power and frequency-to-time mapping enables time–frequency analysis and AOA measurements. The direction ambiguity resulting from single-pulse measurements can be resolved by using two frequency-shifted optical carriers to generate distinct mapping curves. In addition, the theoretical AOA measurement range can be doubled from 90° to 180°. Meanwhile, the frequency measurement ambiguity can also be eliminated by introducing the negative second-order optical chirp sideband to provide a pilot signal. In this way, the frequency measurement range can be doubly extended to the chirp bandwidth. Furthermore, the flexible frequency resolution reconfiguration can be realized by simply adjusting the slope of the low-speed electrical control signals. A proof-of-concept experiment is conducted. The time–frequency analyses are experimentally achieved over the range of 1–13 GHz, with the frequency resolution adjusted from 1.163 GHz to 13 MHz. The AOA measurement is also achieved with the span from −75° to 75° and the error of ±2.5°.