A Compact Multimode OAM Antenna Using Sequentially Rotated Configuration

For multiplex beams of orbital angular momentum, we propose a two-looped concentric uniform circular array consisting of sequentially rotated circular polarization (CP) triangle patches. Generally speaking, the rotation of the CP antenna makes feeding networks free of narrowband phase shifters. Further investigations also reveal that CP performances of elements and the rotation parameters (including directions and centers) are critical factors. Moreover, adopting the triangle patches makes the array compact and wideband. A demonstration with 12 elements is designed and fabricated, whose radius is only 0.76 λ 0 . Simulations and measurements suggest that it could emit circularly polarized vortex waves of modes −1 and −2 at the X-band simultaneously, and its bandwidth is about 8.7%.