Design of A Novel Multi-mode Zero-Feed Multi-passband Microstrip Filter

In this paper, a novel multi-mode zero-feed multi-passband microstrip filter has been proposed. Based on the analysis of the transmission characteristics of the zero-degree feed structure and its zero-point generation mechanism, a T-type dual-mode filter is proposed. After adopting the zero-degree feed structure, additional transmission zeros are generated at both ends of the filter passband, which significantly improves the out-of-band suppression of the filter and the isolation between the passbands, and enhances the ability of the filter to suppress the interference signal. The proposed filter can be applied in the modern wireless communication circuits and systems.