US 12,191,843 B2
Wide-band acoustically coupled thin-film BAW filter
Johanna Meltaus, Espoo (FI); and Tuomas Pensala, Espoo (FI)
Assigned to Teknologian tutkimuskeskus VTT Oy, Espoo (FI)
Filed by Teknologian tutkimuskeskus VTT Oy, Espoo (FI)
Filed on Jun. 27, 2022, as Appl. No. 17/849,744.
Application 17/849,744 is a continuation of application No. 17/008,077, filed on Aug. 31, 2020, granted, now 11,374,551.
Application 17/008,077 is a continuation of application No. 15/893,717, filed on Feb. 12, 2018, granted, now 10,778,186, issued on Sep. 15, 2020.
Application 15/893,717 is a continuation of application No. 13/879,028, granted, now 9,893,712, issued on Feb. 13, 2018, previously published as PCT/FI2011/050891, filed on Oct. 14, 2011.
Claims priority of provisional application 61/392,955, filed on Oct. 14, 2010.
Claims priority of application No. 20106063 (FI), filed on Oct. 14, 2010.
Prior Publication US 2022/0407500 A1, Dec. 22, 2022
Int. Cl. H03H 9/54 (2006.01); H03H 9/56 (2006.01)
CPC H03H 9/547 (2013.01) [H03H 9/564 (2013.01); H03H 9/568 (2013.01)] 20 Claims
OG exemplary drawing
 
1. An acoustically coupled thin-film Bulk Acoustic Wave (BAW) filter, comprising;
a piezoelectric layer,
an input-port on the piezoelectric layer changing electrical signal into an acoustic wave, and
an output-port on the piezoelectric layer changing acoustic signal into electrical signal,
wherein
the ports include electrodes positioned such that acoustic coupling is achieved, the ports having an interdigital electrode structure such that the electrodes are connected alternatingly to the input port and the output port,
the filter is capable of operating in the first order thickness-extensional TE1 mode, and
wherein the number of electrodes is more than ten,
wherein the mass loading by the interdigital electrodes is such that the k=0 frequency of the outside region's TS2 mode is between 93% and 99.9% of the electrode region's TE1 cutoff frequency,
wherein the electrode width W is such that the wavelength of the lateral acoustic wave at the desired odd mode resonance, λodd, is obtained, and
wherein the electrode width W is between 25% and 50% of the desired odd mode resonance wavelength λodd.