Showing papers on "Interdigital transducer published in 1979"

Miniature quartz resonator force transducer

Abstract: The invention relates to a piezoelectric quartz force transducer having the shape of a double-ended tuning fork.

Semiconductor variable capacitance pressure transducer assembly

Abstract: A capacitive pressure transducer assembly having a semiconductor transducer device, a substrate, and a cover for use in conducting a fluid pressure to be sensed to the exterior surfaces of the transducer device. The transducer device may have a glass, silicon or other nonconductive material as a base on which a metal capacitor plate is formed. The other capacitor plate may be formed of doped silicon or other semiconductor material. Also, the substrate on which the transducer device is mounted may have additional and related circuitry implemented in thick film technology (ceramic substrate) or integrated circuit technology (semiconductor substrate).

Encapsulated piezoelectric pressure pulse drop ejector apparatus

Abstract: A pulsed liquid droplet ejecting apparatus wherein a rectangular piezoelectric transducer is arranged abaxially over an ink containing channel with an edge in operating relationship with the channel. The edge of the transducer is held fixed so that on excitation of the transducer by an electrical pulse, the transducer extends towards the channel ejecting a drop. The piezoelectric transducer is coated with a material, which provides shear relief between the piezoelectric transducer and the ejector embedding material.

Surface acoustic wave resonators utilizing harmonic frequencies

Abstract: A surface acoustic resonator including an interdigital transducer configured to generate acoustic waves at at least one harmonic frequency, and a pair of reflection gratings capable of essentially total reflection of the acoustic waves in both fundamental and harmonic modes of operation. One-port and two-port resonators are disclosed, capable of operation at fundamental and harmonic frequencies, to provide a higher frequency of operation without correspondingly higher resolution requirements for manufacturing processes. For single-mode operation at higher frequencies, the interdigital transducer and reflection gratings have different fundamental frequencies, and utilize harmonics of different order but the same actual frequency, such that the resonator functions at a single frequency, which may be, for example, the third harmonic with respect to the transducer fundamental frequency, and the second harmonic with respect to the reflection grating-fundamental frequency.

Interdigital Transducer Models: Their Impact on Filter Synthesis

Abstract: The characterization and comparison of various interdigital transducer (IDT) models used to analyze and design SAW transversal filters are facilitated by partitioning the overall periodic transducer re- sponse into an impulse function, a discrete time sampling function, and m acoustic weighting function in order to describe both wide-band and space harmonic responses. Through this formalism the analog char- acter of an IDT is accounted for by the use of an acoustic function a(f). This perspective is applied to five interdigital transducer models: namely, impulse (equivalent circuit), impulse (sine wave), modified delta function, spectral weighting and space harmonic. The models differ by their a(r) function. The spectral weighting model is de- scribed in detail for its application to apodized and withdrawal weighted transducer design. A new modified delta function model is shown to agree qualitatively with the spectral weighting model for single electrodes, Aperture weighting laws are derived for the models using sampling theory; it is shown that the cla~sicf;~/~ frequency de- pendence holds only for the narrow-band case f = fn and that, in gen- eral, compensation is required for the acoustic weighting function of the model used. Guidelines for evaluating whether or not compensa- tion is needed as well as compensation techniques and alternatives are described.

An acoustic focusing device with an interdigital transducer on a thin piezoelectric plate

Abstract: A new type of Lamb wave device for acoustic focusing is presented. The device has an interdigital transducer deposited on a thin piezoelectric ceramic plate. In the device, Lamb wave is radiated from the surface without the interdigital electrodes into water and interferes constructively at a focal point in water.

Interdigitated electrode ultrasonic transducer

Abstract: An ultrasonic transducer including a thin piezo-electric substrate and an interdigital electrode radiating ultrasonic wave beams with excellent focusing characteristics into a liquid medium in contact with the substrate by applying AC voltages to the electrode.

Analysis of Finite-Width Interdigital Transducer Excitation Profiles

Abstract: Abstruct-In virtually all work on interdigital transducers, it is assumed that the excitation profiie across the width of the transducer is constant. This is a reasonable first approximation to make and in many cases provides acceptable predictions of experimental results Experimentally, the condition is approximated by keeping the interdigital transducer wide. However, as constraints on device size are applied to surface acoustic wave filters, the widths of interdigital transducers are being forced into a range where the transverse electrostatic end effects must be accounted for in describing device performance. As a step toward improved filter synthesis, the three-dimensional electrostatic field of a double electrode interdigital transducer has been found. Variations in the electrode charge distribution have been studied as a function of the distance between the electrode ends and the bonding pads and as a function of substrate anisotropy. Numerical results are provided for end gaps of fh, l h , 2h, and 3h on an isotropic substrate and for a $h end-gap transducer on (YZ) LiNbO,.

PVF2 Transducers for NDE

Abstract: We report on recent calculations and experiments on the broadband properties and impulse characteristics of PVF? transducers and arrays. Experimental wedge transducers show bandwidths of approximately 100% in the excitationofsurface acoustic waves at 7 MHz on nonpiezoelectric silicon nitride ceramic substrates. Computer calculations predict similar bandwidths for interdigital transducer arrays on PVF films for surface acoustic wave excitation on similar substrates. Insertion loss versus frequency m~asure­ ments on bulk longitudinal wave transducers in water at frequencies in the 1 to 30 MHz range show good agreement with theory. 0 A computer program for multilayer piezoelectric films predicts included angles of acceptance exceeding 60 , and control of acceptance angle profiles, in face plates using multilayer PVF2 films. PVF2 bulk wave transducers are made by bonding 25 11 PVF? film (~ l/2" x 1/2") onto brass backing rods witn V-6 epoxy. The PVF film is obtained from Kureha Corporation in st?etched, poled and electroded form. We etch off the aluminum electrodes, which erode quickly when placed in water, and put down a thin layer of chrome followed by a layer of gold (""' 1000 A). These bulk wave transducers have a very flat frequency spectrum up to 20 MHz when radiating into water. 1 This is expected, since the acoustic impedance and velocity of longitudinal waves in PVF2 (3.83 x 105 gm/cmZsec and 2.15 x 105 em/sec, respectively) match relatively wel~ to the impedance and veloc~ty of water (1.48 x 10 gm/cm2sec and 1.48 x 10 em/sec). As the impedance mismatch at the brass/PVF2 interface is large, little energy is radiated into the brass. These characteristics of PVF? result in a clean, nearly bipolar impulse response (Fig. 1). PVF transducers have shown a 60 dB two-way insertion foss at their resonance frequency (A= 4 x film thickness).

Acousto‐optic measurement of bulk wave generation by interdigital transducers excited at SAW resonance

Abstract: The angular distribution and total power of bulk acoustic waves generated by one and 25 finger pair interdigital transducers on y‐z lithium niobate are reported. It was found that the bulk wave radiation from the 25 finger pair grid originates primarily from the transducer ends.

Fundamental charge distributions for surface-wave interdigital transducer analysis

Abstract: The response of transducers with arbitrary polarity sequences can be expressed simply, allowing for electrostatic neighbour effects, by using as an element factor the charge distribution obtained for excitation of one electrode. New calculations of this element factor are presented for a range of metallisation ratios. Treating interelectrode gaps as elementary sources gives an element factor which is less dependent on frequency.

Elastic surfaceewave filter

Abstract: PURPOSE:To simplify manufacture and also to improve the yield by eliminating reflected waves while making it possible to widen electrode finger width and electrode finger intervals, by giving effect the weighting of an interdigital transducer according to electrode finger length CONSTITUTION:In an elastic surface-wave filter, interdigital transducer IDT14 consisting of electrode fingers 12 and 13 is formed on medium 11 which can generate a surface wave and allow it to propagate When an AC voltage is applied between electrode fingers 12 and 13, the generated surface wave propagates on the surface of medium 11 in both left and right directions and at this time, the phase difference between reflected wave Ri from an i-th electrode finger and reflected wave Rj+1 from j+i-th one is in inverse proportion to the wavelength of the surface wave; and when (j) is set to a certain value, the reflected waves differ in phase an odd number greater than pi, so that the reflected waves will cancel each other

Model for s.a.w. scattering by i.d.t. and its application to s.a.w. track changer

Abstract: A superposition model for surface-acoustic-wave (s.a.w.) scattering by an interdigital transducer (i.d.t.) has been developed. In essence, it consists of two steps, (a) The incident s.a.w. induces a voltage across the i.d.t. (b) The bidirectionally radiated s.a.w., due to this induced voltage, is superposed with the incident s.a.w. to yield the scattered s.a.w. field. It is shown to considerably simplify the s.a.w. scattering parameter calculations for i.d.t. The results agree with earlier observations. Scattering parameter calculations of nonuniformly illuminated, resonantly loaded hybrid-junction i.d.t.s (r.l.h.i.d.t.) show that (i) s.a.w.s are unidirectionally radiated over the unilluminated part of the h.i.d.t. and (ii) it is described by a (track-changing) transfer function of bandpass type, with flat bandwidths up to 20% of nearly 0 dB loss, under appropriate conditions. The r.l.h.i.d.t. track changer should, therefore, be useful in realising long delay lines. The attractive feature of the r.l.h.i.d.t. as an s.a.w. track changer is that its implementation is practically feasible even on a low piezoelectric-coupling substrate like ST quartz. However, its main disadvantages are the requirement of (a) multilevel high-resolution lithography and (b) the additional high-Q tuning inductors for resonant loading.

A unidirectional acoustic focusing device with a group of three electrodes

Abstract: A unidirectional device for acoustic focusing has been devised. The transducer consists of a group of three electrodes deposited on two surfaces of a thin piezoelectric ceramic plate. One of them is used as a common earth electrode and is on the substrate surface in contact with water. The others are interdigital electrodes on the other surface. The design and basic focusing properties of the device are described.

A unidirectional three-phase interdigital transducer for acoustic imaging in fluids

Abstract: A new type of unidirectional interdigital transducer for acoustic imaging is presented. The tranducer consists of three electrode groups deposited onto a piezoelectric ceramic plate and can be constructed by using three fingers per wavelength to be driven from a three-phase source.