Modeling and Analyzing High-Order Modes in Periodic-Stub-Loaded Stripline for Wideband Filter Design

Abstract

The high-order modes of the periodic-stub-loaded stripline are studied by using an equivalent circuit, which shows a good accuracy and efficiency. Due to the similarity, the proposed structure is compared with the spoof surface plasmon transmission line developed in recent years, and it reveals advantages for electromagnetic compatibility. Two approaches are introduced to suppress different transmission modes of the proposed structure. The first is the gradual transition structure, which could suppress higher order modes to form a low-pass (dc—9.2 GHz) filter. The second is the half-mode structure. It could suppress the fundamental and the second higher order modes to constitute a bandpass (9.6–27.6 GHz) filter. Both filters have selective transmission modes, broad stop band, steep transition and low-loss features. The prototypes are fabricated and measured. The measured filtering performance agrees well with the simulation data. Benefitting from aforementioned advantages, the proposed filters will be effective alternatives in practical high-speed integrated circuit.