Monolithic crystal filter

Abstract

An improved monolithic crystal filter is disclosed. The filter has input and output ports formed from particular combinations of first, second and third terminals, the latter terminals having been adapted to be connected to certain preselected electrodes of the two adjacent resonators comprising the filter. More specifically, the first terminal is adapted to be connected to one of the electrodes of a first one of the aforesaid two resonators, the second terminal to the other electrode of the first resonator and to one of the electrodes of the second of the two resonators, and the third terminal to the remaining electrode of the second resonator. With the first, second and third terminals so adapted, the employment of the first and third terminals as one of the input and output ports of the filter and the employment of any other combination of two of the terminals as the other one of the input and output ports thereof results in a filter which is found to exhibit two finite frequency attenuation poles whose locations can be varied by varying the filter parameters. As a result, by proper selection of such filter parameters, the attenuation poles of the filter can be made to bracket the filter passband, thereby causing the filter attenuation characteristic to steeply rise near the edges of such band.

Dependencies are inferred from the claim text.