A General Design Methodology for Multichannel SIW Filtering Crossovers With Flexible Frequency Responses

This article presents a robust design methodology for substrate integrated waveguide (SIW) multichannel filtering crossovers (FCRs) with tunable channel center frequencies (CFs), bandwidths, filtering orders, and transmission zeros (TZs). The approach utilizes dual-mode substrate integrated rectangular cavities (SIRCs) operating in orthogonal TE102and TE201modes, which are cascaded and coupled to form anm×ndual-mode cavity array (DMCA). This configuration enables a flexible CF allocation with a maximum frequency ratio of 1.32, while ensuring a high transmission efficiency and strong inter-channel isolation. To further enhance the design adaptability, additional resonant units can be integrated into the DMCA, allowing an independent control over filtering orders and TZs introduced via modal or physical cross-couplings. Generalized coupling topologies are proposed to support a wide range of multichannel SIW FCR architectures. The methodology is eventually validated through two distinct design examples with varied channel counts and frequency responses. These prototypes are synthesized, fabricated, and experimentally characterized, confirming the practicality and effectiveness of the proposed approach.