Research On High Performance Planar Reconfigurable Microwave Diplexer

As a three-port device that separate the transmitting and receiving signals,diplexer is an essential component in the wireless communication system,and its performance will directly affect the performance of the whole system.With the rapid development of wireless communication technologies,spectrum resources are becoming increasingly scarce,and the single frequency band can't meet the demand of the user.Therefore,in order to alleviating the increasingly tight spectrum resources and meet the demand of multiband or multi-service applications,the diplexer with tunable function is highly desired.Based on the projects undertaken during studying for master's degree,this thesis conducted in-depth research on the design principles and methods of reconfigurable diplexers,and several high performance reconfigurable diplexers are proposed.The main research contents include:Firstly,a switchable microstrip diplexer with sixteen types of frequency responses is proposed.The switchable microstrip diplexer has two paths.Each path consists of two pairs of quarter-wavelength uniform impedance resonators(UIRs),where PIN diodes are loaded at open end of the resonator.As a switching device,the PIN diodes are used to control each channel independently to achieve switching among various states.The switchable four-channel diplexer has more freedom in frequency selection due to the independent control of each channel.Finally,the switchable four-channel diplexer with center frequencies of1.53/1.8/2.15/2.4 GHz is designed.Secondly,a new approach to realize reconfigurable diplexer using slot line is proposed.Microstrip-slotline transitions are directly applied to realize the coupling between resonators and microstrip feed lines,and the overall size of the diplexer is reduced.When the extra slotline in the slotline stepped-impedance resonator(SIR)is loaded by varactor,a electrically tunable diplexer is realized.The center frequency for lower channel of the tunable diplexer can be tuned within a tuning range from 1.39 GHz to 1.96 GHz,while the upper channel of the tunable diplexer can be tuned within a tuning range from 2.24 GHz to 2.84 GHz.In addition,within the entire tuning range,the isolation is always better than 28 d B.At last,based on the slotline stub-loaded dual-mode resonator(SLDMR),a bandwidth-tunable diplexer is proposed.By embedding varactor diodes across the two extra slotlines of the slotline SLDMR,the even-mode of the slotline SLDMR can be tuned while the odd-mode is hardly affected.Thereby,a bandwidth tunable diplexer is realized.The fractional bandwidth varying from 12.2% to 18.5% and 10.5% to 17% are realized in the lower channel and the upper channel of bandwidth-tunable diplexer,respectively.