Wideband Anti-Interference Microwave Photonic Measurement for Doppler Frequency Shift and Angle of Arrival

In order to meet the requirements of large instantaneous bandwidth, wide operating frequency range, large dynamic range, and anti-interference for microwave parameter measurement in the new generation radar system and real-time signal processing system, a microwave photonic Doppler frequency shift (DFS) and angle of arrival (AOA) measurement scheme based on Mach-Zehnder modulator (MZM) and acousto-optic modulator (AOM) is proposed in this article. The designed structure can clearly identify the direction of the DFS and avoid the intermodulation distortion and low-frequency interference. In addition, the upper and lower optical sidebands are fully utilized to effectively avoid the frequency error caused by the AOM driver module and improve the measurement accuracy of the system. In the experiment, the error of the microwave DFS at an ultrawide operation frequency from 6 to 36 GHz is between ±0.15 Hz with a clear direction. The micro-DFS (mDFS) measurement is also carried out to demonstrate the advantage of low-frequency DFS measurement. It is also verified that the phase difference error is less than 1° in the AOA measurement experiment. The proposed scheme has advantages such as multifunction and anti-interference, thus having great application prospects.