Optimization Design of Passive Bandpass Filter´s Standing Wave Ratio Based on Poles Placement Technique

The filter´s voltage standing-wave ratio (VSWR) and amplitude-frequency response can not be designed by network synthesis method, therefore the poles placement technique and circuit optimization technique are proposed in this paper. Based on the circuit designed by network synthesis method, parallel inductance is transformed to series inductance and parallel capacitances in the input and output ports of the circuit, so two attenuation poles are increased to make the amplitude-frequency arithmetic symmetrical. Then optimize the circuit by unconstrained optimization method so that the filter´s VSWR is close to 1. The simulation result indicates that the optimal method can make not only the filter amplitude-frequency arithmetic symmetrical, but also the max value of VSWR reduced from 41.297 to 1.20949. So this method is superior to the network synthesis method, it is very valuable in engineering application.