Design and analysis of a low‐pass filter utilizing a slotted‐ground‐plane resonator

Abstract

In this article, the frequency‐response analysis of an H‐shaped slot resonator etched in the ground plane is shown by using transmission‐line analysis and even‐and‐odd mode analysis. Based on a stepped‐impedance structure, we systematically derive a resonance analysis of the slot resonator, addressing resonance conditions, and harmonic responses. The design rule of the slotted‐ground‐plane resonator was successfully derived. The design equations and figures regarding the impedance ratio of the H‐shaped slot resonator have been analytically proven so that the resonant modes can be predicted without electromagnetism simulation software. Aided by the proposed design procedure, we demonstrate a low‐pass filter (LPF) with a unit‐cell topology, which consists of a uniform‐impedance transmission line, an H‐shaped slot resonator, and two C‐like slot resonators which are also designed with the same design rule. By embedding the two C‐like slot resonators inside the H‐shaped slot resonator, several additional transmission zeros are excited in frequency characteristics so that the device achieves wideband rejection performance. Finally, to enhance the frequency characteristics of the LPF, a modified case is also presented by adding a rectangular stub at the transmission line.