US 12,308,826 B2
Bandpass filters using transversely-excited film bulk acoustic resonators
Greg Dyer, Santa Barbara, CA (US)
Assigned to Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed by Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed on Aug. 20, 2021, as Appl. No. 17/407,186.
Claims priority of provisional application 63/144,978, filed on Feb. 3, 2021.
Prior Publication US 2022/0247382 A1, Aug. 4, 2022
Int. Cl. H03H 9/54 (2006.01); H03H 9/205 (2006.01); H03H 9/56 (2006.01)
CPC H03H 9/542 (2013.01) [H03H 9/205 (2013.01); H03H 9/568 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A bandpass filter for a communication band extending between a lower band edge and an upper band edge, the bandpass filter comprising:
a plurality of transversely excited bulk acoustic resonators (XBARs) including a plurality of shunt resonators and a plurality of series resonators connected in a ladder filter circuit, wherein a relative frequency difference between anti-resonance and resonance frequencies of each transversely excited bulk acoustic resonator is greater than a fractional bandwidth of the communications band;
a first capacitor connected in parallel with a first shunt resonator of the plurality of shunt resonators to form a first shunt subcircuit; and
a second capacitor connected in parallel with a first series resonator of the plurality of series resonators to form a first series subcircuit,
wherein the relative frequency difference of each of the XBARs is greater than or equal to 15%, the relative frequency difference being a difference between the resonance and the anti-resonance frequencies divided by an average of the resonance and the anti-resonance frequencies,
wherein at least one of the first capacitor and the second capacitor is a metal-insulator-metal (MIM) capacitor,
wherein a first conductor layer includes a portion forming interleaved fingers of an interdigital capacitor of at least one of the first and second capacitors,
wherein a pitch between two adjacent fingers of the interleaved fingers is greater than 0.05 times a width of at least one finger of the interleaved fingers and less than 0.5 times the width of the at least one finger, and
wherein the MIM capacitor is formed by a portion of a second conductor layer that overlaps a portion of the first conductor layer with an intervening dielectric layer therebetween.