Wide-band acoustically coupled thin-film baw filter

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 filter is capable of operating in the first order thickness-extensional TE1 mode, and
• wherein the mass loading by the top electrode (plateback) is such that the frequency difference between the k=0 frequency of the electrode region's TE1 mode and the outside region's TS2 mode is relatively small.