Normal coordinate monolithic crystal filter
AssigneeThe United States of America as represented by the Secretary of the Army
InventorArthur Ballato
Life of this patent
Estimating the term…
Abstract
Enhancement of proper phase and insertion loss response, reduction of undesired mode couplings, and greater latitude in the design with respect to energy trapping in filters, in addition to enhancement of the dynamic frequency-temperature compensation, as well as stress-frequency compensation is provided by arranging the electrode gap of a monolithic crystal filter so that it is perpendicular to the projection of the normal coordinate or eigenvector of the mode utilized along with making the side edges of the electrodes parallel to the direction of the normal coordinate projection. For the doubly rotated SC cut of quartz, using the c-mode, the normal coordinate projection angle, i.e. the axis along which the electrodes are aligned, is substantially 8.2.degree. from the rotated plate (X') axis.
Claims16
A pizeoelectric monolithic crystal filter compensated for the effects of electrode stresses and temperature transients, comprising:
- a doubly rotated cut of piezoelectric material formed as a plate-like body having a pair of surfaces comprising opposing major faces;
- and
- electrode means, substantially aligned with the projection of the eigenvector (normal coordinate) for the desired operating mode, formed on said surfaces in an energy trapping configuration, and including an electrode gap on at least one of said surfaces, said electrode gap being substantially perpendicular to the projection of the eigenvector, said eigenvector or normal coordinate being the direction of particle motion within said body when excited in said desired operating mode.
A method for compensating a monolithic crystal filter for the effects of electrode stress and temperature transients, comprising the steps of:
- forming a doubly rotated cut of piezoelectric material into a plate-like body having a pair of surfaces comprising opposing major faces;
- and
- forming electrode means in an energy trapping configuration on said surfaces and forming an electrode gap on at least one of said surfaces, said electrode gap being substantially perpendicular to the projection of the normal coordinate or eigenvector for the desired operating mode of said crystal filter, said normal coordinate or eigenvector being the direction of the particle motion within said body when excited in said desired operating mode.
Dependencies are inferred from the claim text.