Showing papers on "Interdigital transducer published in 1975"

Metal enclosed transducer assembly

Abstract: A thick layer of epoxy resin is used to bond together the piezoelectric member and a stainless steel cap to form an acoustic transducer having a broad frequency response, and specific assembling steps are taken to manufacture the transducer with good reproducibility of the characteristics.

Phase reversal ultrasonic zone plate transducer

Abstract: Focused ultrasonic transducer means of the zone plate type are shown for producing a focused ultrasonic wave field without the need for lenses, reflectors, a curved transducer or the like, which transducer means are adapted for ultrasonic nondestructive testing and inspection, ultrasonic examination in diagnostic medicine, sonic heat generation, aerosol formation, and the like. Such transducer means, of course, may be used as a focused ultrasonic transducer receiver as well as a transmitting transducer. The transducer includes a uniformly poled cylindrical shaped body of electromechanically responsive material, such as a piezoelectric crystal, with electrodes formed at opposite parallel faces thereof. A pair of central axially aligned circular electrodes of different size are located on the opposite body faces, together with concentric different size annular electrodes which surround the central electrodes. The radii of the central and annular electrodes are of different lengths such that electrodes on one face overlap adjacent electrodes on the opposite face, with the radial width of the overlapping areas decreasing inversely with increased radial position such that substantially equal overlapping electrode areas are formed. Electrical connection is made between the smallest diameter inner electrode and largest diameter outer electrode such that the large inner circular electrode and annular electrodes function, electrically, as pairs of series-connected electrodes, each of opposite phase. This electrode arrangement, on a uniformly polarized transducer body, results in a transducer with adjacent active opposite polarity zones having opposite deformation, the number of zones being equal to one less than the total number of electrodes employed.

Piezoelectric device for image readout

Abstract: A device which converts the spatial distribution of the received light energy into a modulation of an electric signal. It comprises: a non-piezoelectric substrate; an electro-mechanical transducer in the form of interleaved comb shaped electrodes deposited on the substrate and covered by a piezoelectric layer, and a photoconductive layer covering the piezoelectric layer. The image is projected on to the photoconductive layer and, when the transducer is short-circuited, an elastic wave modulated by the image is propagated in the substrate towards an output transducer which delivers the electric reading signal.

Study of SAW propagation characteristics by frequency‐translated holography

Abstract: Under the condition of continuous acoustic generation the patterns of forward, backward, and standing SAW’s propagating on a y‐cut z‐propagating LiNbO3 crystal were observed clearly by the frequency‐translated holographic technique. The parameters of surface‐wave propagation velocity, reflectivity, and transmissivity for an interdigital transducer could be obtained by this technique.

Guided wave acousto-optic device

Abstract: An acousto-optic device suitable as a correlator, convolution integrator or Fourier transform device. The device comprises a piezoelectric substrate or crystal such as lithium niobate. The substrate is covered by a thin, outer layer having higher index of refraction than the substrate and a thickness on the order of 50 micrometers. Two acoustic transducers such as interdigital transducers are disposed on opposite ends of the crystal to launch two acoustic surface waves in opposite directions. A laser beam is guided through the outer layer and is coupled with the two acoustic waves to generate either a correlation function, a Fourier transform or a convolution integral depending on the signals impressed thereon.

Surface acoustic wave planar resonator using grating reflectors

Abstract: A surface acoustic wave resonator is described which utilizes electrically shorted gratings to form a resonant acoustic cavity where energy is introduced and removed by means of a short interdigital transducer placed in the center. Experimental results are presented for a device with two 100−finger pair gratings and a 9.5−finger pair central interdigital transducer (IDT) and compared with theoretical calculations. The device exhibits a resonant Q of 2300 at 47.55 MHz.

Two−port cavity resonator low−insertion−loss delay line

Abstract: A delay line is described which uses unidirectional transducers, formed by placing a short interdigital transducer (IDT) adjacent to a grating reflector, to realize low insertion losses. Theoretical and experimental results are compared for a device with 10.5 finger pair transducers and 100 finger pair gratings. The measured insertion loss was 2.5 dB at 38.14 MHz.

Particularly oriented plate-like monocrystalline piezoelectric body and acoustic surface wave filter device employing same

Abstract: This disclosure concerns a particularly oriented plate-like monocrystalline piezoelectric body of lithium niobate for use as a substrate in an acoustic surface wave filter device, wherein the orientation of the piezoelectric body of lithium niobate is responsible for a substantial reduction in spurious responses including plate modes. More specifically, the piezoelectric body comprises a plate of lithium niobate having a crystalline lattice orientation as determined by a 46° (ZYW) cut. It has been determined that such a piezoelectric body may be employed as a substrate in an acoustic surface wave filter device to effect an improved filter response in that unwanted spurious responses including those caused by plate modes are removed or substantially reduced from the acoustic signals prior to their conversion into electrical output signals.

Time and space resolution of bulk acoustic waves generated concomitantly with Rayleigh surface waves by an interdigital transducer

Abstract: Surface acoustic waves (SAW) and unwanted bulk acoustic waves (BAW) are radiated simultaneously from an interdigital transducer in commonly used SAW crystal substrates This is a report of tracking BAW groups in their initial passages through a crystal Directly radiated BAW phase fronts are time resolved via tone burst drive and photomultiplier scan of diffraction patterns produced by a 6328‐A laser probe interacting with the BAW Laser tracking of the paths of the energy radiation shows sharply defined BAW beams in 95×95×26‐mm specimens Identity of modes, radiation angles, measured counterclockwise from the backward SAW path, and the approximate amplitudes, measured relative to the SAW or to the main BAW lobe are as follows: (a) In Y‐cut Z‐propagating (PPG) LiNbO3 there are (i) equal longitudinal lobes (LL) at 37 ° and at 81 ° with relative amplitudes (RA) <004; (ii) Y‐Z shear lobes (SL) at 28 °, 54 °, 114 °, and 162 ° with RA’s of 012, 012, 015, and 035 (b) In X‐cut Z‐PPG LiNbO3 there are (i)

LiNbO3 saw device

Abstract: An electro-mechanical transducer comprises a LiNbO3 -piezoelectric substrate containing as an impurity at least one material selected from the group consisting of Ta, Ta2 O5, Pd, SiO2, TiO2, V2 O5 and V, and at least two electro-mechanical transducing interdigital electrode pairs, provided on said LiNbO3 -piezoelectric substrate.

Excitation of surface elastic waves in a piezoelectric layered structure

Abstract: The excitation of Rayleigh surface waves by an interdigital transducer (IDT) on a piezoelectric layered structure has been studied in this paper. The surface wave velocity, optimum finger width, and number of fingers for maximum bandwidth for the IDT have been calculated for several values of the product (ks) of wavenumber and layer thickness. The frequency response and equivalent circuit of the IDT have been determined. Numerical examples are also presented and discussed.Subject Classification: 20.15.

Surface-wave devices using three-phase interdigital transducers

Abstract: Two types of applications of a three-phase interdigital transducer are presented. A transformation circuit (inverter) is used to realize transformation from a three-phase to a single phase and vice versa. When the three-phase interdigital transducer is connected with the three-phase terminal of the inverter, the propagation direction of the excited surface-wave is controllable by interchanging the connection order. A delay line, which is realized by using this property and the large reflection coefficient of the surface wave at a corner edge, could have a delay length close to twice the length of the specimen without using the bottom surface of the specimen as the delay medium. The other application, which is an ultrasonic switching device, is due to the fact that the direction of a signal flow is controllable. The experimental systems and examples of these two devices are shown.

Electromagnetic leakage suppression by interdigital transducers

Abstract: A simple interdigital transducer layout is used in conjunction with a differential amplifier to obtain a high degree of suppression of direct electromagnetic leakages in surface acoustic wave devices. The degree of suppression can be adjusted independently of the device design.

Surface wave filter with symmetrical interdigital structures - uses piezoelectric substrate with comb-shaped electrodes in symmetrical array

Abstract: The piezoelectric filter based on the principle of surface waves is formed with comb-shaped electrodes symmetrically arranged the piezoelectric substrate surface. The electrodes form two systems whose axes of symmetry are spaced in a specified manner related to the wavelength of the main resonance frequency and to a positive integer equal to or exceeding 100.

A new mode of operation for the surface wave convolver

Abstract: A new mode of operation for the surface-acoustic-wave convolver has been discovered. The features of this mode are as follows. 1) It is a degenerate mode, but is detected by an interdigital transducer whose periodicity bears no special relationship to the input transducers. 2) It operates only in an interaction region with bi-directional surface wave amplification. 3) It is more efficient than the usual nondegenerate mode which can operate on the same device. 4) It makes possible highly efficient surface wave convolution with significantly lower spurious response than the usual nondegenerate mode. This device consists of a substrate of YZ LiNbO 3 with a film overlay of CdSe in the interaction region. A dc bias field applied across the electrodes of the output structure provides the bidirectional surface-wave amplification. The device has been used to process PN codes with time-bandwidth products up to 280.

Frequency dependence of unidirectionality of a three-phase interdigital transducer

Abstract: Experimental results on the directionality of a surface wave excited by a three-phase interdigital transducer are presented. The transducer has the characterstic of a bandpass filter with two center frequencies. The propagation direction of the excited surface wave is reversed by changing the carrier frequency.

Pressure measurements very near an electrical arc discharge in a liquid using a lithium niobate piezoelectric transducer

Abstract: The pressure pulse generated by an electric arc discharge in aqueous liquids was measured with a lithium niobate piezoelectric transducer. These measurements are the first time‐resolved pressure pulses recorded in proximity to an arc channel.

Acoustic‐surface‐wave dispersion in periodically metallized structures

Abstract: Periodically varying acoustic properties in the bulk and along the surface of a transmission medium for acoustic surface waves result in velocity dispersion with frequency. This change in the center frequency of interdigital acoustic‐surface‐wave filters, caused by a change in the periodic metallization pattern of the interdigital transducers, has been measured on ST quartz and YZ lithium niobate for single ‐ and double‐electrode transducers.