Microwave-Photonics-Based Vortex Electromagnetic Wave Generation for High Resolution Radar Imaging

In this paper, we propose a method to generate microwave vortex electromagnetic waves with different orbital angular momentums (OAM) using microwave photonic techniques. The proposed system uses polarization-modulation-based microwave photonic phase shifters to control the phase of a uniform circular array (UCA), which enables a large operation bandwidth and large OAM mode numbers. The performance of proposed system is investigated through simulation, in which vortex electromagnetic signals have a bandwidth of 1 GHz (8~9 GHz) with the OAM mode numbers from -16 to 16. Based on the generated vortex electromagnetic signals, high-resolution radar imaging is implemented, which achieves an azimuth resolution of 5.5°, and a range resolution of 17 cm. The proposed method is a good solution to generating broadband vortex electromagnetic signals, which may find applications in high-resolution radar imaging.