Researches On Novel Planar Reconfigurable Filter Components

In the information era,the ever-changing wireless communication technology has brought us numerous convenience.As the key component in wireless communication system,microwave filters play a significant role in communication quality.At present,wireless communication systems are required to be efficient in various frequency bands and operating bandwidths due to the coexistence of a variety of communication standards.This also brings high target on design for microwave filters.In response to this need,combined multi-band filters are common solutions.However,the complexity and difficulty in designing multi-band filters will rapidly increase with more required operating bands.In order to solve this problem and design much smaller,simpler,and higher-performance filters,reconfigurable filters are proposed and studied deeply.The research focuses on planar reconfigurable filter,and the main innovation of this dissertation can be summarized as follows.(I)Research on reconfigurable bandpass filters with constant absolute bandwidths has been done.First of all,mechanism of constant absolute bandwidth has been analyzed and studied to obtain the requirement of constant absolute bandwidth.Then,design principles for constant absolute bandwidth have been put forward to apply for single-band and dual-band reconfigurable bandpass filters.Without using extra controllable coupling structure,constant absolute bandwidth can be easily achieved.(II)Research on reconfigurable bandstop filters with constant absolute bandwidth has been done.Based on microstrip and slot-line transmission lines,a hybrid double-layer structure has been used to design dual-band bandstop filter with tunable lower stopband.In addition,design principles for constant absolute bandwidth have been applied to bandstop filter.Then,a dual-band reconfigurable bandstop filter with independently controlled stopbands and constant absolute bandwidths has been realized.Compared with those of bandpass filters,publications on reconfigurable bandstop filter are much fewer.To a certain extent,these two methods fill this gap.(III)Crossed resonator has been analyzed in detail to determine its resonance and coupling characteristic,then,flexibly multi-mode tuning has been proposed and used to realize tunable frequency and bandwidth.Meanwhile,the difficulty in design of wideband reconfigurable filter can be overcome by using multi-mode resonator.(IV)Combined with defected ground structure and differential-and common-mode separation technology,flexibly multi-mode tuning has been utilized to realized two fully tunable balanced filters.So far,the research on reconfigurable balanced filter is in the initial stage,and there are very few accomplishments.The design methods proposed in this dissertation are simple and effective,which offer a good practical significance and reference value to the reconfigurable balanced filter.