Design Of Multi-band Filter And Balance Filter For Wireless Communication System

With the rapid development of the information age,multi-band communication requirements for microwave RF front-end circuits have been proposed,which has placed more demands on multi-band filters that satisfy multi-band communication,and more importantly,is immune to environmental noise.We have found that a high-performance balanced filter can solve this problem by suppressing common-mode(environment)noise,and it has a frequency-selecting function,so it is widely used.As a key component of the microwave RF front-end,multi-band filters and balanced filters have become the focus of research in the field of microwaves.The miniaturization of circuits is the design of multi-band filters and balanced filters with excellent common-mode rejection.Their respective difficulties.Therefore,research on the design of high-performance common-mode rejection of miniaturized multi-band filters and balanced filters is of great significance.Based on the author's work in master's degree,this paper systematically studies the design of multi-band filters and balanced filters.The main research contents are as follows:(1)Based on the research of the former characteristics of the hairpin ring resonator(HRR),a branch is introduced into the traditional hairpin ring resonator to study the uncoupled three-mode resonance characteristics of the multimode hairpin resonator.A multimode hairpin ring resonator is proposed,and the second mode is the second harmonic of the first mode.The resonance characteristics and multiple transmission zeros are studied by current analysis method.Based on the unique characteristics of the proposed multi-mode hairpin resonator,a new three-band bandpass for mobile communication is proposed and designed.Filters(BPFs).At the same time,the external coupling coefficient of the filter is extracted,and these three bandwidths can be freely optimized.In addition,there are six significant transmission zeros near the passband.This can improve the isolation of the filter.Finally,the fabrication circuit validated the new three-band bandpass filter.(2)Two balanced three-band filters based on multimode microstrip resonators are proposed.And the mode analysis is carried out by using the odd-even mode analysis method,and the common mode harmonic suppression measures(short-circuit branch)/source load coupling and common mode harmonic suppression measures(asymmetric branch)are introduced respectively.The final simulation shows that the former has high out-of-band selectivity and isolation,and both have the characteristics of high-performance common mode rejection.