Design of a dual-band filter based on mode composite structure combining substrate integrated waveguides and slotlines

Abstract

This paper proposes a novel mode composite structure that combines substrate integrated waveguides (SIWs) and slotlines, offering a compact solution for a dual-band filter targeting both microwave and millimeter-wave bands. The TEM mode of slotlines and TE modes of SIWs within a single substrate layer are transmitted simultaneously. They can share ports, feeding circuits and feeding apertures, which means the proposed structure is compact, offering efficient integration. Particularly, slotlines embedded are capable of generating low-frequency resonances with feeding circuits, and are able to regulate the field distributions of TE modes in high bands. The performance of the filter is validated through simulation and measurement, demonstrating bandwidths from 15.49 GHz to 17.42 GHz and from 33.05 GHz to 35.10 GHz, with excellent out-of-band rejection more than 20.24 dB. It is suitable for Ku and Ka applications.