Patent ID: 7855621

Claim:
A reflection-type bandpass filter for ultra-wideband radio data communications, the reflection-type bandpass filter comprising: a substrate formed by laminating a conducting layer and a dielectric layer; and a microstrip line comprising a conductor of a non-uniform width and provided on the dielectric layer, wherein a width distribution of the microstrip line in a lengthwise direction is set such that an absolute value of a difference in reflectivity at a frequency f in regions f<3.1 GHz and f>10.6 GHz and a reflectivity in a region 3.7 GHz≦f≦10.0 GHz is not less than 10 dB, and a variation of a group delay in the region 3.7 GHz≦f≦10.0 GHz is between −0.2 ns and 0.2 ns; and wherein the width distribution of the microstrip line is set using a design method based on an inverse problem leading to a potential from spectral data in a Zakharov-Shabat equation.