ABSTRACT
Electromechanical bandpass filters have been given names, or at least have retained their names, to differentiate one type from another. For each of the filter types the major limitation on minimum bandwidth is the frequency shift of the filter with temperature. The filter center frequency is usually determined by a single length or thickness dimension of the resonator. An exception is the flexure resonator where both length and thickness determine the frequency. The low-frequency limits are determined by the allowable length of the resonator or its minimum allowable thickness, in the case of flexure modes of vibration. Since most electromechanical filters, which include Surface acoustic wave filters, use piezoelectric transducers, we will concentrate on filters of this type. Electrical conductors are recognized by their being connected by nodes, whereas the mechanical filter coupling wires are denoted by simple lines.
