Theoretical Research And Design Of Reconfigurable RF Filter

With the development of multi-standard communication system,reconfigurable RF filters have attracted more and more research and attention.In this paper,related studies on reconfigurable SIW filters are carried out,including the theories of reconfigurable RF filter and the design methods of actual SIW structures.Firstly,the filter coupling matrix is analyzed in this paper,including the construction of N+2 coupling matrix,similar transformation and reconfiguration of matrix.A reconfigurable coupling matrix with variables is proposed to provide theoretical guidance for the actual reconfigurable filter design.Due to SIW has the advantages of low cost,low power consumption,relatively high Q value,high power processing capability and high density integration,this paper introduces the feed styles of SIW filter,and we study the theoretical analysis and concrete implementation of the reconfigurable SIW cavity,reconfigurable bandwidth design and reconfigurable external Qe value design.Based on the above design theories and methods,a compact dual-band HMSIW bandpass filter is designed.The dual-mode HMSW resonators form a dual-band filter through vertical hybrid coupling,which greatly reduces the size of the filter.The bandwidths of two passbands can be designed independently.In addition,three transmission zeros are introduced to the filter,which greatly improve the out-of-band rejection.One transmission zero can be flexibly designed to the left or right of the second passband.The dual-band HMSIW filter can be extended to multi-pole filter.The simulated 3-pole HMSIW filter has five transmission zeros,and both two passbands have a quasi-elliptic response.Based on the QMSIW structure,this paper designs a reconfigurable dual-band QMSIW band-pass filter.The two passbands can be continuously tuned,and without affecting each other.Each passband requires only one control voltage,and the tuning is convenient.The simulated and measured results are in good agreement.In order to further reduce the size of the filter,this paper designs a fully adjustable miniaturized EMSIW bandpass filter.By loading stubs and varactors on the EMSIW cavity,not only the miniaturization of EMSIW filter is achieved,but also the center frequency reconfigurability of the EMSIW filter is innovatively implemented.The EMSIW cavity is electrically coupled through the edge,and the varactor diode is loaded between the EMSIW cavities to achieve bandwidth reconfigurability.In addition,two transmission zeros are introduced to improve the out-of-band rejection above the passband.Both simulated and measured results show that the filter center frequency and bandwidth can be continuously tuned.Compared with other published fully adjustable SIW filters,the fully tunable filter achieves excellent performance while achieving the smallest size.