Design And Realization Of High Performance Miniaturized Mixed Coupled Filters

Microwace Filters based on mixed-cross coupling matrix theories are thoroughlystudied in the thesis. General Chebyshev filters with Mixed-cross coupling are proposedto reduce the number of resonators and ease the design. The proposed filters withcompact size, high frequency selectivity and controllable transmission zeros, aresuitable for modern microwave communication system.First of all, the paper illustrates the elementary principles of the N and N+2crosscoupling matrix, then mixed-cross coupling matrix with frequency-variant coupling isestablished to locate the position of transmission zeros based on N and N+2stepsChebyshev methodology. Genetic and Solvopt algorithm are combined to optimize andextract the mixed-cross coupling matrix for coupling aim matrix and erified byexamples. The effects of the mixed coupling term’s location in the coupling matrix areanalyzed.Secondly, a stepped impedance resonator (SIR) mixed-coupled structure whichintroduced considerable value of electric and magnetic coupling was presented toconstruct a series of single/dual-band passband filters. To improve the frequencyselectivity and out-of-band rejection, multiple transmission zeros were introduced nearthe passband by mixed coupling and harmonic effects. Based on this structure, acascade trisection (CT) mixed-cross coupled filter was presented which introduced threetransmission zeros close-to-passband and have high rectangle coefficient. The dual-bandbandpass filter based on mixed SIR structure resonators achieves high out-of-bandrejection and isolation by transmission zeros. A compact size is achieved by embeddingresonator1for passband1into resonator2for passband2. A SIR hairpin structure withradial stubs is presented in the end. Compared with the convention SIR hairpin line theproposed SIR hairpin has better stopband characteristics. Quasi-ellipticlowpass/bandpass filter can be designed flexibly with the proposed SIR. Wider stopbandcan be obtained by embedding a Π capacitance network inside the filter structure.Thirdly, a compact hexagonal mixed-coupled resonator with more compact stucture which is suitable for multi-resonator cascaded is proposed. We can design aseries of mixed-coupled filter based on this resonant structure. A high shape factor isobtained by ransmission zeros can be created in the vicinity of the bandpass usingmixed effect and harmonic effect shape factor.The final part of this thesis involves a miniaturized dual-layer metal resonator,multiple mixed coupling filters with small size and high frequency selectivity based onthe dual-layer metal resonators are presented. The mixed coupling structure is dividedinto two kinds of structure including reinforced type and weakened type based on thewinding direction of the spiral inductance, and a transmission zero closed to thepassband was produced in the weakened type second-order filter with mixed coupling.Novel3th-order and4th-order filters with mixed cross-coupling was fabricated byintroducing mixed coupling into cross-coupling. The filters have more transmissionzeros out of the passband and higher out high band rejection and shape factor.