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A new lumped parameter electrical circuit model of a disk-wire mechanical filter is described. The disk resonator model is based on a knowledge of its natural frequencies and its equivalent mass at various points; the coupling-wire model is based on transmission line concepts. In order to maintain a topological correspondence between the mechanical and electrical circuits, the mobility analogy has been used throughout. The new model has provided a means for understanding the effect of coupling-wire orientation on the selectivity of simple disk-wire filters. It is shown that variations in wire position affect the equivalent mass of "diameter" modes, causing changes in the finite attenuation poles located near the filter passband. Also discussed are problems associated with using "disk-pair" data in the design process. A solution based on an analysis of the improved filter model is discussed.
Date of Publication: Jan. 1968