Beam convergence and 2-D imaging using orthogonal frequency diversity-based synthetic vortex waves

Vortex electromagnetic waves carrying orbital angular momentum (OAM) offer new possibilities for radar imaging but suffer from beam hollowing and energy divergence. Existing beam-converging methods based on orthogonal waveform diversity require numerous phase-coded symbols and lack anti-jamming capability, with high computational overhead. To overcome these limitations, this paper proposes an Orthogonal Frequency Diversity-based Synthetic OAM (OFD-SOAM) radar system that generates non-hollow beams through a novel frequency–mode mapping strategy, enhancing jamming resilience while reducing memory and computational load. Specifically, a new signal model is developed by jointly applying cyclic phase shifts and frequency offsets across the array elements. An echo processing framework is designed to accurately reconstruct the vortex phase structure. Additionally, a two-dimensional OFD-SOAM imaging method is proposed to obtain superior resolution. Simulation results confirm the proposed system's advantages in robustness and efficiency compared to conventional OAM-based radar.