Linearized Microwave Photonic Doppler Frequency Shift and Angle of Arrival Measurement System

A microwave photonics Doppler frequency shift (DFS) and angle of arrival (AOA) measurement system with a large spurious-free dynamic range (SFDR) is proposed in this article. The system integrates the linearization of microwave photonic systems with DFS and AOA measurement, achieving a high-precision, wideband measurement capabilities while enabling long-distance, high-quality signal transmission. By effectively suppressing the third-order intermodulation distortion (IMD3), second-order intermodulation distortion (IMD2), and DC components, the SFDR is significantly enhanced, and the micro-DFS measurement capability is expanded. The system enables long distance transmission and measurement through the suppression of periodic power fading, facilitates DFS measurement and direction discrimination via the implementation of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i>/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> down-conversion, and wide-angle AOA measurement is achieved through phase analysis. Compared to traditional down-conversion system based on dual-parallel Mach–Zehnder modulator (DPMZM), the proposed system demonstrates a 10 dB improvement in SFDR3. Furthermore, experimental verification shows a DFS measurement error of ±0.2 Hz, while the AOA measurement error is ±1.5° within a range close to 150°.