A wideband omnidirectional filtering patch antenna with high selectivity

Abstract

A wideband omnidirectional filtering patch antenna with high selectivity is proposed in this article. The annular ring is surrounded by the hexagonal patch with inner circle, whereas a series of shorting vias are regularly distributed among them and a copper top hat is suspended right on the top of the radiator, respectively. And, omnidirectional pattern is mainly performed on account of the symmetry and center-fed structure. In addition, broadband performance is achieved by merging three resonant modes, which include the TM01 and TM02 modes of the annular ring and the TM02 mode of the hexagonal patch with inner circle. Taking advantages of the hexagonal patch and six shorting vias in it, two radiation nulls are provided in the upper band. Besides, another radiation null is generated in the lower band by reason of the top hat and other shorting vias. As a result, an ideal quasi-elliptic bandpass response, high selectivity, and good out-of-band rejection are obtained simultaneously. The proposed filtering patch antenna, with a profile of 0.056 λ 0, shows a wide impedance bandwidth of 30.2% from 2.05 to 2.78 GHz. The average gain in the passband is about 6.5 dBi, and the out-of-band suppression level is greater than 15 dB in the wide stopband.