Torsional mechanical filters at 500 kHz

A torsional mechanical filter configuration has been developed for operation in the commonly used IF (intermediate frequency) range of 500 kHz, utilizing third torsional-mode electromechanical transducer resonators in conjunction with second torsional-mode interior resonators. This structure was derived by extension of the lower-frequency (typically 128-kHz) fundamental torsional-mode technology, with methods developed to avoid relatively closely spaced spurious modes in the wire coupling elements. Finally, the observed transition-band skewing has been shown to be caused by coupling-wire weld stiffness in conjunction with the wire´s transverse elasticity, and the configuration of staggered coupling wires has been shown to eliminate this effect