Dual-band Omnidirectional Filtering Antenna with High Selectivity

Abstract

A dual-band omnidirectional filtering antenna with high selectivity is proposed in this paper. The annular ring is surrounded by the hexagonal patch with inner circle, while a series of shorting vias are regularly distributed among them. Besides, another radiating patch and a copper top hat are added right on the top of former components, respectively. In this design, omnidirectional pattern is mainly performed on account of the symmetry and center-fed structure. Lower operating band is mainly achieved by merging three resonant modes, which include the TM 01 and TM 02 modes of annular ring and the TM 02 mode of hexagonal patch with inner circle. And, higher operating band is dependent on the resonant mode of added radiator and the TM 11 mode of hexagonal component. Taking advantages of the hexagonal patch and eight shorting vias in it, two radiation nulls are provided near the higher band edge. Besides, another radiation null is generated in the lower frequency by reason of the top hat and other shorting vias. As a result, an ideal quasi-elliptic bandpass response and high selectivity are obtained simultaneously. The proposed filtering patch antenna with the bandwidths of 33.2% and 9.5% is achieved and the results are presented.