Research And Design Of Dual-band/Tri-band Bandpass Filters

Since twenty-first Century,the rapid development of 2G-5G wireless communication technology(GSM,WCDMA,UWB,DCS,WLAN,WIMAX,LTE,etc.)greatly stimulated the rapid development of the filter.In order to meet the different standards of various communication technologies,high-performance,miniaturized,multi-band,low-cost and easy-integration microwave passive devices came into being.As one of the essential components of wireless communication system,more and more experts and scholars pay more attention to the advantages of microwave filters,such as fine out-band suppression features,frequency selectivity and miniaturization,etc.The main work of this thesis is to study and design high-performance,compact dual-/tri-band bandpass filters(BPFs).The main contents are as follows:Firstly,a dual-band and a tri-band bandpass filters were designed,respectively,based on a symmetric stub loaded resonator(SSLR).First of all,the basic principle,structural characteristics,resonant characteristics and the application of the stepped impedance resonator(SIR)are described in detail based on the basic theory of the filter.Then,a symmetric shorting-stub loaded resonator(SSLR)is designed based on the SIR.The detailed analysis of the symmetric open-/short-stub loaded resonator is given.Finally,high-performance,miniaturized dual-/tri-band microstrip BPFs are designed using the resonator.The characteristics of the filters are analyzed.The filters make full use of the direct coupling of the capacitive source and load,the stub-loading,the pseudo inter digital structure and the SIR technology.The filters have the characteristics of miniaturization,controllable frequency,controllable bandwidth,high selectivity and good harmonic suppression.Finally,the technology of transmission zeros of designed filters is studied.Secondly,a dual-band and a tri-band bandpass filters were designed,respectively,based on a asymmetric stub loaded resonator(ASLR).This section presents a SIR loaded asymmetric open/short stub technology,which can design more compact BPFs,The characteristics of ASLR are analyzed.Finally,the dual/tri-band BPFs aredesigned using asymmetric short-stub loaded SIR.A detailed analysis of the characteristics of the filters is given based on the simulation and experimental results.Thirdly,a coaxial cavity band-pass filter is designed based on the actual project requirements of a communication operator.The basic theory,design index and design process of the coaxial cavity filter are discussed.Finally,the steps such as modeling and simulation of the AWR circuit topology,HFSS single/double cavity and tap simulations,Auto-CAD drawing and physical testing verify the filter fully meeting the design targets.At present,the designed filter has been successfully applied to the operator's base station transceiver system.