An SIW filtering antenna array with quasi-elliptic gain response based on intercavity bypass coupling

In this article, a filtering antenna array based on substrate integrated waveguide (SIW) is proposed with quasi-elliptic gain responses for the first time. Two radiation nulls in the gain responses at two sides of the frequency band edges are designed by applying a novel intercavity bypass coupling scheme. First, by carefully analyzing the bypass coupling between the in-band and out-of-band modes in a single oversized TE103 mode cavity resonator, quasi-elliptic filtering responses are achieved for a two-output filter. Afterward, those cavity resonators coupled with the two outputs are replaced by cavity-backed slot antennas to achieve the proposed filtering cavity-backed slot antenna array. Only one cavity is required in our design to achieve the two transmission zeros and the function of power divider. As a result, the complexity of the proposed filtering antenna array is reduced. A prototype operating at Ka band is designed, fabricated and measured with a center frequency of 28.5 GHz and fractional bandwidth of 1.25%. Similar characteristics can be observed between the gain response of the proposed filtering antenna and the transmission responses of the two-output filter. The proposed SIW filtering antenna array has great potential to be integrated into millimeter-wave transceiver modules. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:191–198, 2016.