A Low-profile Dual-function RF Device Integrating Filter and Antenna

keywords:two-port RF device  dual-polarized antenna  two-order filter  low profile  discriminating coupling  wide stopband  operating frequency ratio

Abstract:This paper introduces a two-port RF device integrating a dual-polarized (DP) antenna and a two-order filter with a low profile. Discriminating coupling is introduced to suppress the harmonic of resonators, contributing to a wide stopband for filter.At the same time, the resonators themselves function as the feeding lines for a patch antenna without occupying extra area, providing DP radiation performances. The operating frequency of antenna locates at the second harmonic frequency point of filter. Due to the discriminating coupling scheme, the harmonic mode will not affect the antenna performance, which means the operating frequency ratio of the antenna and filter can be extended. For verification, the proposed two-port RF device is fabricated and measured. Experimental results show that the device functions as a DP antenna at 1. 81 GHz, and simultaneously as a filter at around 0. 9 GHz. For antenna function, the measured peak gain of 5. 5 dBi and 5. 8 dBi are obtained for horizontal and vertical polarization states, respectively. Good agreement in the radiation performances can be observed between two polarized states. With respect to filter function, its operating frequency locates at 0. 8 GHz with high selectivity and a stopband from 0. 9 GHz to 2 GHz.The total profile of the device is 2. 5 mm. With above performances, the proposed design can be a candidate for the future multichannel communication systems with low-profile and high-integration level.