Study On Key Technology Of Planar Passive Components In Microwave Front-End

With the rapid development of modern wireless communication systems and the continuous emergence of new technologies,the evolution of microwave and millimeter wave systems have been going towards high performance,miniaturization,multifunction and low cost.The planar passive filter and power divider/combiner,which directly affect the performance of the whole systems,are still the key components in microwave communication systems.Thus,study on high-performance and miniatureized passive devices is valuable,because it could help to reduce the size and the weight and improve performance of the systems.By adopting stepped-impedance resonator(SIR),defected grounded structure(DGS),multi-mode resonators,and new structures of Gysel and Wilkinson,several novel passive components of filters and power dividers are investigated in this thesis.The main research contents are summarized as follows:Firstly,two novel internal loaded hairpin structures are proposed based on stepped-impedance resonator.Meanwhile,the corresponding transmission matrix and the equivalent L-C circuits are presented.By utilizing two sets of this resonators,several lowpass filters with high selectivity and wide stopband are designed.The embedded part won't enlarge the whole size and could enhance the slow-wave effect.Thus,the proposed filters have great advantage of compact size.Secondly,a novel interdigital DGS resonator and its equivalent LC model are presented.Compared with conventional DGS of only one transmission zero(Tz),this resonator exhibits three Tzs and a better skirt performance.And the characteristics of passband could be adjusted through tuning the dimensions of the fingers.Based on the propsed structure,a lowpass filter,composed of stepped-impedance mircostrip line and two cascading DGS units,is implemented on Rogers5880.Besides,by increasing the number of the fingers,the cutoff frequency will decrease,resulting in miniaturization.A demonstrated lowpass filter with single stage has better selectivity over other DGS filters.Thirdly,a short stub-loaded multimode resonator is proposed and applied to design ultra-wideband(UWB)bandpass filter.Compared with the same type of filters,the proposed one obtains a wider bandwidth.In addition,a stubs loaded ring resonator is studied.Under weak coupling between the resonator and source/load,six resonant modes and three Tzs are observed.Two of the Tzs are close to edge of the low-end and high-end of the passband,respectively.While the other one is located within the passband.Based on the resonator,an UWB bandpass filter is designed and it has the merits of high selectivity and high suppression level.Fourthly,dual-band bandpass filters are investigated.A novel complementary split-ring resonator(CSRR)with stub loaded is presented and used in the design of dual-band filters.By tuning the dimensions of stubs,the number of Tzs between the passbands can be adjusted,thus the design flexibility could be enhanced.Measurements indicate that the filter has closely spaced passbands,high isolation,and suppression of the second harmonic.Moreover,a crossed H-shaped resonator is proposed and discussed by odd-/even-mode analysis.By cascading two identical units and introducing additional coupling between the even modes,the central frequency and bandwidth of the second passband can be individually adjusted.Furthermore,a four-mode ring resonator with open stubs loaded is applied to design a dual-band bandpass filter,and the two passbands can be adjustable.The fabricated filter demonstrates sharp skirt and it could be suitable for local communication systems.The filters in this chapter possess the flexibility in design process,making them have great potential application to multi-band communication systems.Fifthly,a tri-band bandpass filter using an open and short stubs loaded resonator is proposed.The third passband is actually a harmonic response.By tuning the impedance ratio of the ring resonator,the locations of the passbands could be placed suitably.The demonstrated tri-band filter is suitable for 5G WiFi application.Finally,the power dividers are studied.On the basis of summarizing Wilkinson and Gysel structures,a new combination topology is obtained.The proposed structure has the advantages of wide bandwidth of Wilkinson and good heat-handling of Gysel.Besides,an out-of-phase Wilkinson power divider is presented.The impedance and electronic length of transmission lines are deduced in detail by odd-/even-mode analysis.Measured results show that the out-of-phase power divider could achieve equal division in a narrow band.