Orbital Angular Momentum Imaging Based on Waveform Diversity and Rotational Array

Vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has been exploited in radar imaging realms in recent years. However, the radiation energy pattern caused by the Bessel amplitude modulation limits the OAM-based applications in the long distance. To solve the radiation energy divergence problem in radar realms, the imaging method based on waveform diversity (WD) and rotational array is developed in this article. The energy hollow along the beam axis is avoided by the orthogonal waveform design during the radar illumination process. Then, the echo demodulation approach is proposed, and the corresponding imaging model is established. Furthermore, a highly efficient imaging scheme based on rotational array is designed, where the OAM multiplexing approach is proposed and large OAM index can be used for imaging by virtual synthesis. Both simulation results and experimental results in an anechoic chamber are provided to demonstrate the effectiveness. This work can promote the application of OAM technology in realistic scenarios.