A Bandpass Filter Using Half Mode SIW Structure with Step Impedance Resonator

Min-Hang Weng,Yi-Chun Chung,De-Li Chen,Ru-Yuan Yang,Chin-Yi Tsai

doi:10.3390/electronics10010051

Abstract

This paper presents a miniaturized bandpass filter, which uses half mode substrate integrated waveguide (HMSIW) structure with embedded step impedance structure (SIS). By embedding the stepped impedance structure into the top metal of the waveguide cavity, the center frequency can be quickly shifted to a lower frequency. The operating center frequency of the proposed bandpass filter (BPF) using HMSIW resonators with embedded SIS is tunable as functions of the parameters of the SIS. The design curve is provided. A filter example of the center frequency of the filter at 3.5 GHz is fabricated and measured, having the insertion loss |S21| less than 3 dB, and the return loss |S11| greater than 10 dB. The transmission zeros are located at 2.95 GHz and 3.95 GHz on both sides of the passband, both of which are lower than 30 dB. The simulation result and the measured response conform to the proposed design concept. The proposed HMSIW filter design is in line with the current 5G communication trend.

Highlights

The measurement of the fabrication bandpass filter (BPF) showed the center frequency of 3.25 GHz, the insertion loss |S21 | less than 2.5 dB, and the return loss|S11 | greater than 10.5 dB
We have shown that with the introduction of step impedance structure (SIS) on the top metal of the half mode substrate integrated waveguide (HMSIW) resonator, the operating frequency of the filter can be reduced
The entire resonant properties are combined with the properties of the Substrate integrated waveguide (SIW) cavity and the microstrip resonators, which can further be used to tune the frequency and the bandwidth of the BPF formed by the HMSIW resonator

Summary

Introduction

With the advent of the 5G communication era, new communication frequency bands and new communication standards are continuously being announced. In the RF front-end system, a small-sized BPF is responsible for separating the radio signals transmitted and received by mobile phones from different frequency bands [1]. Component miniaturization and module integration are the current trends in BPF design. Among the filters in the Sub-6 GHz frequency band, low temperature co-fired ceramic (LTCC) filters and surface acoustic wave (SAW) filters are most commonly used in mobile communication devices [2,3]. In the development of microwave and millimeter-wave filters, the choice of the substrate material and filter structure will affect the transmission loss, which is a very critical design consideration

Objectives

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Conclusion