Simultaneous and Unambiguous Measurement for Doppler Frequency Shift and Angle of Arrival of a Microwave Signal with High Precision

A photonic scheme for simultaneously measuring both the Doppler frequency shift (DFS) and angle of arrival (AOA) of a microwave signal based on a polarization division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM) is proposed. In our scheme, the single-sideband (SSB) modulated signals via PDM-DPMZM are divided into two branches, and so two ac power-phase mapping functions with higher slopes are formed by different polarization processing. Since one ac power-phase curve serves as a calibration line, the system can realize unambiguous AOA measurement with the phase range of -180 degrees similar to 180 degrees. The value and direction of DFS can only be determined using an electrical spectrum analyzer (ESA). In addition, the scheme has a larger operating bandwidth because no filter is required. Simulation results show that the AOA from -83.92 degrees to 83.92 degrees is measured with an error of +/- 0.9 degrees, and the DFS measurement within +/- 100 KHz is realized with an error less than +/- 5 x 10(-3) Hz. The characteristics of low error, high precision, and wide bandwidth are important for microwave signal detection.