Research On The Miniaturization Of Plannar Diplexer For Mobile Communcation Application

Mobile communication is one of the most rapid development industry. As an importantcomponent of RF front-end of mobile communication system, microwave diplexer acts asboth filter and spliter. The performance of the communication system is directly related to themicrowave diplexer, thus the fully and detailly research on the microwave diplexer has veryimportant significance. The thesis focus on the miniaturization of plannar diplexer. Concreteresearch content includes the following parts:Firstly, a diplexer based on stub-loaded dual-mode resonator is proposed for4G wirelesscommunication. The main advantage of stub-loaded dual-mode resonator is that a compactnarrowband bandpass filter can be easily realized and a transmission zero is also produced inthe stopband of each channel, which improves the isolation between two channels. Isolationof the diplexer is further improved by introducing the source-load coupling.Secondly, a novel diplexer based on dual-mode stub-loaded resonators is presented. Oneresonant mode in a common resonator and two resonant modes of two individual dual-moderesonator constitute the lower or upper passband with three transmission poles. Moreover,three transmission zeros from three stub-loaded resonators are properly allocated in the lower,middle and upper stopbands, thereby improving the isolation between two desired channels.The diplexer is in final designed for UMTS and WCDMA system..Thirdly, a novel HTS diplexer based on double-resonance spiral resonators (DSRs) andsingle-resonance spiral resonators (SSRs) is proposed. Single-resonance spiral resonators areused in individual Channel, and the DSRs are used as common resonators for both Channels.DSRs are designed using a modified stub-loaded resonator, which can produce two resonantfrequencies for both Channels of the diplexer. Because the SSRs and DSRs are dissimilarresonators, their different spurious frequencies result in a wide stopband. Moreover,resonators are connected by a novel coupling structure to ensure both high couplingperformance and compact size. Based on the method, a diplexer is designed for1.8GHzmobile and2.4GHz WLAN systems.Finally, a novel mcirostrip diplexer with novel coupling structure based on steppedimpedance resonators is investigated. Two coupled stepped-impedance resonators are used ascommon resonators for both Channels. Based on the this method, a diplexer with the centralfrequency of1.89GHz and2.35GHz for4G wireless communication application is fabricatedand measured.