volume | PIER Journals

Abstract

This paper presents a novel fourth-order bandpass filter with high selectivity and out-of-band suppression based on equivalent magnetic side wall cavities (MSWCs). By loading a via hole into an MSWC to produce a zero mode as a non-resonating node and using the dual MSWC modes TEM₀₀₁ and TE₁₀₀ as resonant modes, a modified doublet with two poles and two transmission zeros (TZs) can be formed. Three types of frequency response, either quasi-elliptic or asymmetric, can be obtained and designed flexibly. The TZs can be located on both sides of the passband or both on just one side. The mechanisms for generating the TZs are analyzed, and the adjustment of the TZ positions is discussed. The proposed four-pole quasi-elliptic filter with four TZs is a cascade of two such doublets with two different types of asymmetric response. It has been fabricated and measured to validate the design. Comparison is made with some previous work on substrate integrated waveguide filters. The developed filter is free from radiation and relatively compact among high order filters with multiple adjustable TZs based on cascaded cavities of the substrate integrated waveguide type.

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Dr. Min-Ming Sun

Prof. Yun-Sheng Xu

Dr. Qiao Zhang

Dr. Chang Chen

Dr. Lingyun Zhou