Research On Microwave Filters Based On Novel Plannar Structures

With the rapid development of wireless communication systems,as the key part of the circuits,high-performance wideband/multi-band filters and balanced filters have been a hot research field and attracted considerable attention among researchers.This dissertation,combining the theory research and project applications,has put forward a series of new type of planar filtering structures,mainly including a novel coupling topology based on stub-loaded resonators,quasi-lumped hybrid resonator and multimode slot resonators.Then we have explored their applications of single-end and balanced microwave filters.Firstly,in chapter 2,a novel type of coupling structure between E-shaped stubresonators is proposed,which provides much more flexibility to control the coupling coefficients of every single resonant mode and is ulitized to realize a high-performance quad-band bandpass filter.Then a multi-stub loaded resonator with electrical coupling effect is analyzed to design a high selectivity notched UWB filter.By tunning the coupling strength,an odd resonant mode can be independently controlled.In addition,by introducing the source-load coupling cell,a novel SIW with multiple extra transmission zeros and extened stopband is realized.Secondly,in chapter 3,the coupling lines with various boundary conditions are analyzed in detail.Accordingly,a series of balanced filters with high common mode rejection and closely transmission zeros are proposed.Among them,the second-order filter possesses one transmission zero at one side of the passband;the third-order filter has two transmission located at either side of the passband,which enhances the selectivity highly.In addition,a balanced dual-band bandpass filter is proposed by using the balanced coupling lines and stepped impedance resonators.Thirdly,in chapter 4,a new type of hybrid resonator with compact size and two flexibly controlled resonant modes is proposed.According to the Chebyshev filter prototype and the realization of dual-band filter,a synthesis of hybrid resonator based dual-band filter is realized,which can control the passband bandwidths and ripples indepently.Accordingly,a second-order hybrid resonator bandpass filter is designed,which has the advantages of mulitiple transmission zeros and closely spaced bands.Then a balanced dual-band bandpass filter is realized based on the mirrored single-endfilters.Fourthly,in chapter 5,two methods for the analysis of slots are presented and compared.Accordingly,the electrical characteristics of single-and dual-stub loaded slotline resonators are fully investigated based on duality principle,which combine the advantageous features of microstrip stub-loaded resonators in DM filtering performance and slotlines in CM suppression.Then a series of second-and third-order balanced bandpass filters are designed,which have closely transmission zeros for high selectivity.Besides,single-end and balanced dual-band bandpass filters are also realized based the dual mode single-stub loaded slotline resonator.Finally,the summary of the whole dissertation was given,and the future work was also presented.