A compact SIW dual-functional design with integrated filter and self-diplexing antenna

This paper proposes a compact dual-functional design (DFD) which integrates a bandpass filter (BPF) and self-diplexing antenna in a half-mode substrate-integrated waveguide (HMSIW) cavity. The design consists of four eighth-mode SIW (EMSIW) sub-cavities that are formed by etching three slots on an HMSIW cavity. Two of the sub-cavities are coupled to form a BPF with low insertion loss with a controllable transmission zero and a wide out-of-band rejection > 33 dB. In contrast, the other two sub-cavities are used to create a self-diplexing antenna with wide frequency tunability (2.8–5.0 GHz) with two additional narrow slots and high isolation (>22 dB). Detailed parametric studies confirmed that tuning of self-diplexing antenna has no significant impact on the performance of integrated BPF. An equivalent circuit model of the design is developed and validated with simulation and measurement results. The proposed design has a simple and compact structure, good isolation, and controllability, making it suitable for modern handheld wireless systems.