Thin film resonator filter having at least one component with different resonant frequency sets or electrode capacitance

Abstract

A thin film resonator (TFR) filter circuit including a plurality of TFRs connected in a series-shunt or shunt-series arrangement between input and output ports of the filter. A method is provided that allows for the shifting of resonant frequency sets in each TFR in respective series arms and shunt legs of the TFR filter circuit, as opposed to a conventional concatenating approach using a plurality of chained-up building blocks of TFRs, where resonant frequency sets in each of the series arms are equal, and where resonant frequency sets in each of the shunt legs are equal. Additionally, each TFR in the filter may have a unique parallel plate electrode capacitance, as opposed to the conventional concatenating approach where all series arm electrodes in the root filter design have equal capacitance, and where all shunt leg electrodes have equal capacitance. By shifting the resonant frequency sets and/or varying the electrode capacitance of the TFRs, a wider passband width may be achieved for a given return loss performance, as compared to conventionally designed filter circuits.