A Mode-Reconfigurable Orbital Angular Momentum Antenna With Simplified Feeding Scheme

In this communication, an orbital angular momentum (OAM) mode-reconfigurable antenna based on a uniform circular array (UCA) is presented. To realize multiple switchable operating states while maintaining a relatively simple structure, a simplified feeding scheme is developed. By introducing a set of optimal reference phases for different OAM modes, the tunable phase states for the entire array are degenerated, which leads to a reduction in the total number of required phase states. Then, the excitation phases are decomposed into two parts and generated by the reconfigurable radiators and reconfigurable feed network, respectively. In addition, p-i-n diodes are selected as switches to control the operating states of the radiators and feed network. Therefore, OAM-mode switching capability can be obtained by altering the direct current (dc) bias configurations of the diodes. The antenna design is validated by both simulation and measurement. Results indicate that the proposed eight-element array antenna produces six operating states corresponding to OAM modes l = ±1, ±2, and ±3. The measured overlapped band among the states with
$\vert \text{S}_{\mathbf {11}}\vert < -15$
dB covers 2.33–2.73 GHz. Moreover, the proposed antenna also features the advantages of easy fabrication and low cost.