| Abstract: | A focusing interdigital transducer (IDT) and corresponding single- and
dual-port piezoelectric devices are disclosed. The focusing interdigital
transducer, which generates Lame acoustic waves, permits operation at
significantly higher frequencies than those possible with traditional
IDTs. The focusing IDT employs multiple arced fingers formed both above
and below the piezoelectric layer to improve coupling efficiency by
coupling through both the e.sub.31 and e.sub.33 piezoelectric
coefficients to the piezoelectric layer. By optimizing both anchor design
and location, acoustic wave losses are minimized, thereby improving the
device's quality factor Q. Through proper bus design and selection of the
number of IDT fingers, a device's impedance can be tuned for a given
application. The focusing IDTs may be used in single-port filter devices
and dual-port transformer devices. The single- and dual-port devices may
operate at a single frequency, at two frequencies, or over a band of
frequencies. |