Study And Design Of Miniaturized Wideband Filters

The resource of electromagnetic spectrum becomes more and more intense for growing in demand of communication with the development of wireless communication.Therefore,wideband system has become inexorable trend for the future wireless development.As one of the key elements in wideband communication system,wideband bandpass filter not only be required high frequency selectivity and wide passband,but also needed more compact structure and simple processing.Therefore,it has become very important to design wideband passband filter with high performance and miniaturized structure.Based on analysis of odd-even mode and synthesis of cross-coupled resonator,this dissertation pays more attention to design miniaturized wideband filters in three passband frequencies.The main research contents and achievements include several sections as following.Firstly,as an effective method to design wideband filter,odd-even mode method has been deeply introducted in this paper.A short-stub added resonator has been analyzed as an example with this theory.At the same time,the theory of generalized chebyshev filters has been described in detail.N order and N+2 order cross-coupling filter have been synthesized by coupling matrix.Target optimization algorithm is used to optimize and extract mixed cross-coupling matrix.Example verifies the validity of the theoretical analysis.Secondly,in order to satisfy the requirements of Federal Communications Commission(FCC)for passband in 3.1-10.6 GHz,a novel four-mode resonator with central short-stub loaded is proposed.Based on odd-even mode theory,it can be proved which parameters of the structure affect the four resonant frequencies sharply.Based on the optimization of the fold stub,novel UWB filter not only has perfect frequency selectivity,but also has compact structure.Notch characteristic has been studied for UWB.Bring in folded stubs and DGS in filter ports is proved possessing one single adjustable notch.Two notchs are generated by coupling a dual mode resonator in the four-mode resonator.Thirdly,for the application of 5G base station in the fifth generation mobile communication,compact wideband filters with 9-15 GHz passband have been designed.Based on dual-mode ring resonator,a Folded-stub loaded Square Loop Resonator(FS-SLR)is proposed.The relationship of resonator structure with transmission zero has been quantificated by odd-even mode method.FS-SLR filter has more degree of freedom in adjusting transmission zeros.Frequency selectivity has been improved by cascaded two FS-SLRs.The square loop resonator with two embedded folded-stubs loaded(EFS-SLR)makes the filter more compact for 5G application.Finally,based on one project of an institute,a filter with high performance and miniaturized structure is requiremented.A four-mode SSL-SIR filter base on Low Temperature Co-Fired Ceramic(LTCC)is proposed.Parameters extraction for couple matrix improves that the structure has favourable in-band characteristics in 1.6-2.9 GHz.Furthermore,by introducing cross-coupling between two nonadjacent resonators,wideband filter could obtain better frequency selectivity.Fabricated filter is only 6×6×1.3 mm3 in size,witch proves the reasonability in design method.