A novel differential filtering patch antenna with high selectivity

Abstract

A novel differential filtering antenna with high selectivity is proposed. The antenna is mainly composed of three different-size patches, a slot, a pair of differential feeding lines, and a line resonator. An air gap is adopted to improve the impedance bandwidth and the filtering performance. The line resonator helps to generate high common-mode (CM) rejection. Owing to the parasitic concave and convex patches, the filtering performance and the bandwidth of the antenna are enhanced. The parasitic concave patch affects the lower band-edge selectivity while the parasitic convex patch influences the upper band-edge selectivity. In addition, the frequencies of two radiation nulls can be controlled independently to achieve two high sharp roll-off rates by adjusting the lengths of the parasitic patches. Considerable impedance matching bandwidth is achieved through an aperture coupling. Finally, a prototype of the differential filtering antenna is fabricated and tested. The measured results are in good agreement with the simulated results, showing an impedance bandwidth of 9.9% and an average realized gain of 7.5 dBi. Besides, two filter zero transmissions located at 3.40 and 3.84 GHz produced two radiation nulls.