Acoustic vibrator with variable sensitivity to external acceleration
First Claim
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1. An acoustic vibrator subject to external stresses comprising:
- a substrate;
first electrode means arranged on said substrate for creating a mechanical mode shape of said substrate, said mechanical mode shape having a predetermined characteristic frequency in the absence of external stresses, said first electrode means being electrically connected to a first external means for supplying a first group of signals; and
second electrode means electrically connected to a second external means for supplying a second group of signals, said first and second external means being separate from each other, said second electrode means arranged on said substrate for generating bias stresses by application of electrical bias signals, said second electrode means being arranged around the first electrode means such that said electrical bias signals do not effect said mechanical mode shape, said second electrode means arranged to detect external stress on said substrate and adjust said biasing signals in response thereto;
wherein frequency perturbations caused by external stresses are compensated for by said electrical bias voltages applied to said second electrode means.
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Abstract
Biasing electrodes on a piezoelectric acoustic vibrator alter the sensitivity of the acoustic vibrator and can be used to compensate for external stresses applied to the acoustic vibrator. The biasing electrodes and the circuitry providing electric signals to them are separate from the RF circuitry feeding the RF signal electrodes of the acoustic vibrator. Biasing electrodes can be used on bulk acoustic wave devices or surface acoustic wave devices. The biasing electrodes can be energized by a static D.C. voltage source, or can be used in a dynamic biasing arrangement to provide instantaneous compensation for changing environmental conditions.
38 Citations
16 Claims
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1. An acoustic vibrator subject to external stresses comprising:
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a substrate; first electrode means arranged on said substrate for creating a mechanical mode shape of said substrate, said mechanical mode shape having a predetermined characteristic frequency in the absence of external stresses, said first electrode means being electrically connected to a first external means for supplying a first group of signals; and second electrode means electrically connected to a second external means for supplying a second group of signals, said first and second external means being separate from each other, said second electrode means arranged on said substrate for generating bias stresses by application of electrical bias signals, said second electrode means being arranged around the first electrode means such that said electrical bias signals do not effect said mechanical mode shape, said second electrode means arranged to detect external stress on said substrate and adjust said biasing signals in response thereto; wherein frequency perturbations caused by external stresses are compensated for by said electrical bias voltages applied to said second electrode means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification