Showing papers on "Interdigital transducer published in 1972"

Self‐Consistent Theory of Interdigital Transducers

Abstract: The generation and absorption of surface waves by an interdigital transducer with uniform finger spacing are calculated with the aid of a surface dielectric constant related to the TM‐wave impedance. It is found that the response of an infinite transducer can be calculated with complete consistency, i.e., the field due to the distortion of the piezoelectric medium is correctly included in the determination of the distortion. For a finite transducer, the solutions given are in error only at lines on the surface at either end of the transducer, and are therefore accurate when the transducer is long. It is found that the parallel equivalent circuit derived in the weak coupling approximation is a reasonably accurate representation of the transducer when the coupling is strong and the transducer long, but that the central resonance is then distorted.

Piezoelectric transducer and noise making device utilizing same

Abstract: A noise making device, using a piezoelectric transducer, includes a piezoelectric element mechanically coupled to a substrate and an electrical circuit for energizing the transducer. The piezoelectric element includes a piezoelectric crystal, first and second electrode means carried by the crystal, and means dividing one of the electrode means into electrically isolated areas so as to provide a third electrode means.

Excitation of Shear Elastic Waves by an Interdigital Transducer Operated at Its Surface‐Wave Center Frequency

Abstract: The excitation of shear elastic waves by an interdigital transducer operated at its surface‐wave center frequency is discussed. It is shown experimentally for the high‐coupling orientation of LiNbO3 that the shear‐wave power radiated by an interdigital transducer may be an appreciable part of the input electrical power even at the surface‐wave center frequency. The mode conversion of surface waves to shear waves at a receiving transducer is also considered. It is shown that the shear‐wave radiation pattern of an electrically driven interdigital transducer is well described by treating the transducer as a phased‐array antenna.

Use of rotated electrodes for amplitude weighting in interdigital surface‐wave transducers

Abstract: Amplitude weighting in an interdigital surface‐wave transducer array may be achieved by misaligning the electrodes with the incident‐wave phase fronts. Since in this method all the electrodes are full aperture, the problems of diffraction loss and phase‐front distortion are avoided. Transducers employing this method of weighting to achieve a flat bandpass response were used to construct delay lines on quartz and lithium niobate, and their performance is shown to be in reasonable agreement with predictions.

Self-Consistent Theory of Interdigital Transducers

Abstract: The generation and absorption of surface waves by an interdigital transducer with uniform finger spacing are calculated with the aid of a surface dielectric constant related to the TM‐wave impedance. It is found that the response of an infinite transducer can be calculated with complete consistency, i.e., the field due to the distortion of the piezoelectric medium is correctly included in the determination of the distortion. For a finite transducer, the solutions given are in error only at lines on the surface at either end of the transducer, and are therefore accurate when the transducer is long. It is found that the parallel equivalent circuit derived in the weak coupling approximation is a reasonably accurate representation of the transducer when the coupling is strong and the transducer long, but that the central resonance is then distorted.

Annular 3m class piezoelectric crystal transducer

Abstract: The transducer of this invention utilizes an annular crystal of the 3m class operated in the shear mode with the shearing surfaces and the axis of the acceleration parallel to the Z axis of the crystal. When the crystal is composed of lithium niobate or lithium tantalate, the transducer has high efficiency and when the crystal is composed of lithium niobate it operates effectively over a very wide range of temperatures, including high temperatures above 1,000 DEG F.

Method for using interdigital surface wave transducer to generate unidirectionally propagating surface wave

Abstract: Disclosed is a unidirectional interdigitated surface wave transducer having at least three discrete arrays of conductive elements, each array comprising, in a comb-like structure, a plurality of electrodes electrically interconnected in parallel and having a periodicity corresponding to one acoustic wavelength of the resonance frequency of the transducer. The discrete arrays of electrodes are deposited upon a piezoelectric substrate in an interleaved pattern to define an interdigitated transducer. Respective electrodes of a given array are substantially equidistantly spaced apart from electrodes of the other arrays and are electrically insulated therefrom. The arrays of electrodes are positioned upon the substrate such that there are at least three electrodes per acoustic wavelength at the resonance frequency. A voltage of different phase is simultaneously applied to each array of electrodes by means of novel broadband phase shifting circuits to generate an acoustic wave that propagates in only one direction along the substrate.

Electromechanical frequency selective devices

Abstract: Electromechanical frequency selective filters are disclosed wherein a wafer of piezoelectric material converts an electric input signal into a surface wave by means of an input transducer comprising electrodes of conductive material on the surface of the wafer. The surface wave is converted into an electric output signal by means of an output transducer comprising two combshaped interdigital electrodes made of conductive material and arranged on the same surface of the wafer of piezoelectric material. Either or both of the transducers are split into a plurality of sub-electrodes which are electrically insulated from one another. Signals produced at output transducer sub-electrodes are separately applied to associated unidirectional amplifiers whose outputs are combined to obtain a desired overall output signal.

Composite surface-wave transducer

Abstract: A transducer for generating and detecting surface elastic waves in a piezoelectric material may include a metalic grating on the material forming one electrode of the transducer and a counter-electrode separated from the grating by a dielectric layer.

The grating array: A new surface acoustic wave transducer

Abstract: A novel surface acoustic wave transducer, called the grating array, is described. Experimental results obtained at 9.2 MHz on PZT and 290 MHz on LiNbO 3 are presented which demonstrate the capability of this transducer to efficiently generate and detect Rayleigh waves on piezoelectric materials.

Weighted interdigital transducers for smoothing of ripples in acoustic-surface-wave bandpass filters

Abstract: The transfer function of acoustic-surface-wave (a.s.w.) bandpass filters exhibits ripples in the passband and sidelobes in the stopband, owing to the finite length of the sin x/x-shaped interdigital transducer used for the filter's impulse-response synthesis. A direct means of overcoming this inconvenience by weighting the interdigital transducer according to smoothing functions, such as those of Fejer and Lanczos, which were developed for the suppression of ripples due to the Gibbs phenomenon, has been devised. The reported results show the effectiveness of this simple approach to the improvement of a.s.w.-filter capabilities.