Researches On Mixed Electric And Magnetic Coupling Filters

Due to the advances in modern electronic device processing technology and theexplosion in demand for voice, data and video communication capacity, modern microwavecommunication technology has excited widely attention and researches. Especially, thelimited frequency resource has imposed the division of frequency to become narrower.Narrow filters with small size and high performance are particularly important in thesesystems. Based on this demand, it requires us to construct an innovative method or newconstruction to realize quasi-elliptic function response besides the traditional methods usingcross-coupling and source-load coupling.This dissertation focuses on the design technique of the mixed electric and magneticcoupling filter. The main contributions of this dissertation can be summarized as follows.First of all, the background of the trend of microwave communication systems isintroduced. And the latest domestic and international researches of high-performancemicrowave filters are presented.Secondly, the performance parameters of the filter are introduced. Give a straightforwardintroduction of the two common filter design methods: low pass prototype synthesis methodand the coupling matrix synthesis method, which provide the basic theory for the furtherwork.Moreover, based on half-wavelength hairpin-comb resonator, the phenomenon of mixedelectric and magnetic coupling between resonators is analyzed. This method can be used todesign single-band and dual-band bandpass filters. Three kinds of bandpass filters with highselectivity, which are using this structure, are proposed and analyzed(1) Inline cascaded third-and fifth-order filters with quasi-elliptic responses(2) Cascaded trisection mixed electric and magnetic cross-coupling filter(3) Mixed electric and magnetic coupling hairpin-comb dual-band bandpass filterIn addition, based on quarter-wavelength stepped impedance resonator, it can be easilyrealized high-order filters by utilizing the mixed electric and magnetic coupling betweenresonators. This method can be used to design single-band and dual-band bandpass filter. Aninline cascaded third-order filter with controllable transmission zeros, high selectivity andwide stopband is designed and fabricated.Finally, there is a research on TE01mode dielectric resonator. A novel method to designTE01mode dielectric resonator filter with controllable transmission zeros is proposed. One cavity TE01mode dielectric resonator filters with transmission zero have been analyzed andresearched. Based on this new method, the quasi-elliptic function responses are realized ininline cascaded TE01mode dielectric resonator filters. Instead of using dedicated couplingprobes, or extra cavities, as required by conventional techniques, cross coupling is realized bychanging the orientation of selected resonators. All the introduced dielectric resonator filterscan be easily designed and manufactured.All the proposed filters are simulated, fabricated and measured. The simulated andmeasured insertion loss and return loss curves show good agreement, which verify thefeasibility of the design methods in this dissertation.