Design of a Microstrip Filtering Antenna without Extra Circuits and Its Application in Orbital Angular Momentum (OAM) Filtering Antenna

In this paper, a microstrip filtering antenna is proposed with gain-filtering response. The antenna consists of an E-shaped radiator and a slotted U-shaped coupling structure. Three radiation nulls are obtained by the radiator, the U-shaped coupling structure, and the two slots. The filtering antenna has no extra circuits, which indicates that it is easy to design. A 4-element filtering OAM antenna array is also designed to validate its applicability in OAM antennas. Measured results show excellent performance of the array, which also make it a potential candidate for 5G wireless communication devices.