The Study And Design Of Cavity Bandstop Filters

With the rapid development of modern wireless communication system,the co-site interference problem resulting from different closely located communication systems is growing.To suppress the interference signal and solve the signal blocking problem,it has practical significance and engineering application value to carry out the research of microwave filter,especially the bandstop filter.By utilizing HFSS EM software,six cavity bandstop filters have been designed as follows:1)By using the stepped impedance resonator(SIR),the U-shaped and S-shaped bandstop filter have been designed.The main transmission line is bended and the spatial arrangement of the filter has been optimized.The feasibility and reliability of filter miniaturization design have been investigated.2)Based on the design method of bending the resonator,three kinds of parallel coupling line(PCL)narrow-band filters have been designed to expand the out-passband.To realize the miniaturization of the filter,the capacitance loading technology and SIR-PCL resonant design have been studied.The series resonance of lumped capacitance and the fringe capacitance of the cavity have been analyzed in detail.3)Based on thetransmission-zero-generating irise technology,the inductive and capacitive window design method of coupling irise have been analyzed.The feasibility of adding transmission-zero for filter is verified.A waveguide coupling irises bandstop filter with microstructure is designed.The filter performance is analyzed and the miniaturized characteristicis is introduced.Finally,the engineering application prospect of each filter is discussed in this thesis.All filters designed in this paperprovide a reference for the design of compact and high performance miniaturized bandstop filter.