The Piezo-Electric Resonator in High-Frequency Oscillation Circuits

Cady developed theoretically the motional admittance circle diagram of the piezo-electric resonator. The object of the first part of the present paper is an experimental verification of Cady´s theoretical considerations regarding motional admittance. The effect of an air-gap between the resonator and the electrodes upon the motional admittance is also studied theoretically and experimentally. The determination of the equivalent electrical constants of the piezo-electric resonator with an air-gap is developed by a simple mathematical treatment. The relation between motional admittance and size of electrodes is discussed, as well as the experimental arrangement when a high voltage is to be impressed upon the resonator.