bandpass filter is a crystal with polylithique, sub polar attenuation in the band out of less than

摘要

A bandpass crystal filter of the type which uses coupled resonators and has a shunt capacitor at the junction between pairs of coupled resonators exhibits a stopband loss-frequency characteristic which is approximately symmetrical and monotonic. In some applications, it is necessary to sharpen up at least one side of the filter and this extra loss could be obtained if one or more frequencies of infinite loss could be added in the adjacent stopband. By connecting the parallel combination of a capacitor and a two-terminal quartz resonator across the junction between pairs of coupled resonators, the loss-frequency characteristic may be modified to include frequencies of infinite loss in the lower stopband.