Showing papers on "Transducer published in 1969"

Analysis of Interdigital Surface Wave Transducers by Use of an Equivalent Circuit Model

Abstract: Immittance, transfer, and scattering characteristics are studied for acoustic surface wave transducers of the interdigital electrode form. Linear network models are used to represent the transducer as a chain of identical three-ports which are acoustically in cascade but electrically in parallel. Transducer operation at acoustic synchronism is described theoretically and compared to current experimental data for transducers operating at 100 MHz and fabricated on lithium niobate. Favorable lithium niobate configurations for efficient, broad-band transducer operation are given. Scattering characteristics as a function of electric load are discussed. Low values of acoustic reflection loss are predicted theoretically and observed experimentally when the electric load and transducer capacitance are in resonance. The frequency dependence of transducer radiation immittance is studied, and the response is found to be analogous to the response of an endfire antenna array.

Piezo-Optical Birefringence Modulators: New Use for a Long-Known Effect

Abstract: A general description is given of a long-neglected use for the piezo-optic or photoelastic effect (stress-induced birefringence). An acoustic vibration, such as a fundamental extensional mode in a bar or long thin plate, is set up in a block of isotropic transparent material, such as glass or fused silica; the vibration is sustained by a transducer. The resulting modulated birefringence can be used in a variety of ways, notably to produce a beam of alternately left- and right-circularly polarized light for circular-dichroism measurements. Strains of the order 10−5 are required, considerably below the breakage point for most materials. Because advantage is taken of the high Q of the vibrational modes, typically 103 to 104, very small transducer power is needed, usually less than 1 W. The literally enormous useful angular aperture, of the order 50° total cone angle, makes the device far superior to Pockels or Kerr cells for many applications. Reference is made to current practical realizations and to present and future uses of the device.

Excitation of elastic surface waves by spatial harmonics of interdigital transducers

Abstract: The electric field distribution from a surface wave interdigital transducer is investigated. Expressions for the various spatial harmonics and the capacitance of a transducer applied on an anisotropic, small-coupling propagation medium are derived. Experiments are consistent with the calculations.

Design of Surface Wave Delay Lines with Interdigital Transducers

Abstract: Design aspects and tradeoffs are presented for nondispersive, analog Rayleigh wave delay lines with interdigital transducers. Design procedures are based on a one-dimensional piezoelectric transducer model whose applicability has been confirmed by experimental data taken on transducers operating at 100 MHz. For transducers with series inductive tuning, optimum aperture and number of interdigital periods are given for several attractive piezoelectrics, such that insertion loss and phase dispersion are minimized while bandwidth is maximized. High-triple transit suppression designs are given for bidirectional transducers, implying some sacrifice in insertion loss. Using directional transducers, low insertion loss and high triple transit suppression are achieved simultaneously at some sacrifice in bandwidth. Finally, two approaches are given for making with presently available piezoelectrics, bandwidths higher than those attainable with a single tuning inductor. The first of these uses a coupled resonator electrical matching network, while the second employs a transducer with graded periodicity.

A Quartz Resonator Pressure Transducer

Abstract: A digital pressure transducer has been developed utilizing a precision 5 MHz piezoelectric quartz resonator. The circular resonator exhibits linear changes in frequency when subjected to radial compressive stresses. A cylindrical quartz tube, integral with the circular resonator, acts as a diaphragm and transfers and concentrates the stress from the applied pressure onto the periphery of the resonator. Since the tube and resonator are fabricated from a single quartz crystal, nonelastic effects are minimized. The transducer has a dynamic range of 107and a pressure range of 0 to 104psia.

Implantable bio-data monitoring method and apparatus

Abstract: A system for monitoring a condition of a body function or organ or device implanted within a body includes a sensor or transducer responsive to that condition or a change in it connected to a signal means capable of producing an audible, visual or heat signal of variable intensity indication to control the energization of the signal means from a source of energy. The sensor and signal means and the source of energy may be implanted within the body with the signal means sufficiently near the surface of the skin so that its energized state may be detected from outside the body.

Characteristics of Microwave Acoustic Transducers for Volume Wave Excitation

Abstract: Transducers which utilize acoustoelectric conversion in a piezoelectric film, plate, or surface have found wide application for generating planar volume-acoustic waves at microwave frequencies. A review is given of the electrical impedance, conversion loss, and bandwidth characteristics for piezoelectric film or plate transducers which vibrate in one-dimensional thickness extensional or shear modes. The transducer response is related to the electric and acoustic parameters that describe the transducer configuration, and experimental examples are given to illustrate the operation of typical transducer configurations. Methods for achieving low conversion loss and/or broad bandwidth are discussed and experimental examples given. Tables of bulk material constants are supplied for commonly used plate and film devices, and transducer fabrication methods are reviewed. Other types of volume wave transducers, such as those utilizing a single piezoelectric surface, a diffusion layer in a piezoelectric semiconductor, or mode conversion at a boundary are also briefly discussed.

Excitation and Detection of Surface Elastic Waves in Piezoelectric Crystals

Abstract: The amplitude of the surface elastic wave produced by the application of an alternating voltage to an interdigital arrangement of electrodes on the surface of a piezoelectric medium is determined. The electric field produced by the surface electrodes is calculated subject to the assumption that the piezoelectric coupling of the material can be neglected. This electric field acts as the forcing term for the inhomogeneous elastic equation, which is then solved to obtain the amplitude of the surface wave generated by the transducer. A reciprocal relationship between the excitation and detection problems is used to obtain the power extracted from the surface wave by an interdigital arrangement of surface electrodes. Measurements made on single crystals of quartz and cadmium sulfide are found to be in good agreement with theoretical predictions. The maximum value of the product (efficiency×fractional bandwidth) for a surface‐wave transducer is calculated. For an interdigital surface‐wave transducer on the basal plane of CdS, the maximum value of this product is found to be 7.8×10−2. It is shown that one can connect linear pairs of surface electrodes in an appropriate binary code so as to obtain high efficiency and large bandwidth transducers.

Combined optical and magnetic transducer

Abstract: A combined optical and magnetic transducer for sensing both optical and magnetic properties of an article, for example, a piece of paper currency or other document having both visible and magnetic markings to be tested or read, an information-bearing medium such as a data-recording tape to be read, or the like. The transducer comprises a magnetic-sensing head having a transparent gap separating the poles of the magnetic core of the head, a photoelectric element being disposed in the head in alignment with the gap. Outside the head, one side of the article contacts or is in close proximity to the poles at the gap, and the article is illuminated by a light source, so that both magnetic properties and optical properties of the article may be detected simultaneously during relative movement of the article and the transducer.

Visual tuning electronic drive circuitry for ultrasonic dental tools

Abstract: Solid state electronic circuitry for driving the magnetostrictive transducer of ultrasonic dental tools is described, wherein tuning to resonance is controlled by circuit adjustment to maximum brightness of a tuning indicator lamp. Variation of brightness of the lamp as a function of tuning accuracy is achieved by feeding a reference voltage proportional to the excitation current flowing through the ultrasonic transducer to the input of a differential amplifier stage to compare it with a preset reference voltage. The varying output voltage thus derived is amplified to provide an energization current for the indicator lamp which will be proportional to the transducer excitation current and thus an indication of tuning to resonance.

Characterization of Piezoelectric Transducers Used in Ultrasonic Devices Operating Above 0.1 GHz

Abstract: Piezoelectric transducers for ultrasonic devices operating at frequencies above 100 MHz are presently being made either by thin‐film deposition techniques or by bonding thin plates to the substrate and lapping them to the required thickness. In either case the performance of the transducers cannot be evaluated separated from the device, and the evaluation is complicated by the presence of intermediate layers and spurious circuit elements. This paper uses Mason's equivalent circuit to critically appraise the validity of methods used to evaluate transducer performance from loss and admittance measurements made under these circumstances. Computed families of curves are presented, spanning the practically important range of mechanical impedances and coupling factors. Experimental data from a ZnO film and a LiNbO3 thin‐plate transducer on fused quartz substrates are presented to demonstrate the application of equivalent circuit descriptions to obtain the coupling factors.

Acoustic bulk-surface-wave transducer

Abstract: Bulk and surface waves are strongly coupled at a corrugated surface Experiments have demonstrated transduction losses of less than 1dB and bandwidths of 20% Methods of implementation at high frequencies are discussed

Transducer for ultrasonic machine tool

Abstract: An ultrasonic transducer for machine tool purposes comprises two elongated coaxially disposed members coupled to each other with one of the members being adapted to oscillate as a halfwavelength resonator at the predetermined frequency, typically 20 kHz. The transducer is designed to be coupled to a drill of conventional design and when so coupled causes a tool bit to rotate while undergoing axial oscillation at the predetermined frequency.

Grain flow rate monitor

Abstract: A COMBINE HARVESTER IS PROVIDED WITH A CIRCUIT FOR DETECTING THE FLOW RATE OF GRAIN AT ANY PARTICULAR POINT IN THE COMBINE. THIS CIRCUIT INCLUDES A HIGH FREQUENCY PIEZOELECTRIC TRANSDUCER LOCATED AT A CONVENIENT POINT IN THE PATH OF FLOW OF THE GRAIN. AS GRAIN AND OTHER CROP MATERIALS IMPINGE, THE TRANSUCER DEVELOPS VOLTAGE SPIKES, A PARTICULAR FREQUENCY RANGE OF WHICH IS DETECTED BY A FREQUENCY DETECTING CIRCUIT WHICH AMPLIFIES THE DETECTED SPIKES. NEXT THE SIGNAL IS FED TO AN AMPLITUDE DETECTING CIRCUIT TO DETECT A RANGE OF AMPLITUDES OF VOLTAGES SPIKES ABOVE A PREDETERMINED AMPLITUDE WHICH INCLUDES SPIKES PRODUCED BY A GRAIN IMPINGEMENT ON THE TRANSDUCER, BUT EXCLUDES THE SPIKES PRODUED BY OTHER THRESHED CROP MATERIAL. THE DETECTED VOLTAGE SPIKES ARE THEN CONVERTED BY A MONOSTABLE MUTIVIBRATOR INTO SQUARE WAVE FORM AND SENT TO A METER CIRCUIT WHERE THEY ARE AVERAGE AND VISUALLY DISPLAYED ON A METER. IN THIS MANNER THE COMBINE OPERATOR CAN INSTANTANEOUSLY KNOW THE FLOW RATE OF GRAIN AT ANY SPECIFIED POINT IN THE COMBINE AND CAN DETERMINE FROM THIS FLOW WHETHER THE COMBINE IS OPERATING EFFICIENTLY.

Variable capacitance detecting devices

Abstract: VARIABLE CAPACITANCE DETECTING DEVICES ARE DESCRIBED IN WHICH A CONDUCTIVE MEMBER INSULATED FROM THE FIXED AND MOVEABLE ELECTRODES IS DISPOSED WITHIN THE DEVICE ACROSS THE LEAKAGE PATH OF ONE OR MORE OF THE ELECTRODES. AN AMPLIFIER OF UNITY GAIN IS CONNECTED TO ESTABLISH THE SAME INSTANTANEOUS VOLTAGE AND PHASE ON THE CONDUCTIVE MEMBER AS THAT ON THE ELECTRODE. WHERE THE ELECTRODES ARE WITHIN A HOUSING FROM WHICH LEADS ARE FED THROUGH TO EXTERIOR CIRCUITRY, THE LEAD FROM THE CONDUCTIVE MEMBER SURROUNDS THE LEAD FROM ONE OF THE ELECTRODES. A PRESSURE TRANSDUCER FOR NON-CONDUCTIVE FLUIDS IS SHOWN IN WHICH THE CONDUCTIVE MEMBER IS A CONDUCTIVE COATING APPLIED TO A DIELECTRIC PLATE, SURROUNDING THE FIXED ELECTRODE WHICH IS ALSO CARRIED BY THE PLATE. TWO OF THESE PLATES ARE MOUNTED ON OPPOSITE SIDES OF A DIAPHRAGM TO ACHIEVE A BALANCED TRANSDUCER, AND LEADS FROM THE CONDUCTIVE BANDS PASS THROUGH APERTURES IN THE PLATE.

Noncontact ultrasonic interface viscosity and percent solid detecting device

Abstract: AN INTERFACE, VISCOSITY AND PERCENT SUSPENDED SOLID ULTRASONIC DETECTING SYSTEM COMPRISING A TRANSDUCER ADAPTED TO BE AFFIXED TO THE OUTSIDE OF A CONTAINER WALL, MEANS FOR ENERGIZING THE TRANSDUCER SO THAT AN ULTRASONIC PULSE IS TRANSMITTED THROUGH THE CONTAINER WALL, ACROSS THE CONTAINER CONTENTS, AND REFLECTED OFF THE OPPOSITE CONTAINER WALL BACK TO THE TRANSDUCER, AND MEANS RESPONSIVE TO THE REFLECTED PULSE, AND DEPENDENT ON THE EXTENT OF ATTENUATION OF THE REFLECTED PULSE, FOR INDICATING THE LOCATION OF AN INTERFACE BETWEEN TWO STRATIFIED IMMISCIBLE LIQUIDS IN THE CONTAINER AND/OR FOR INDICATING THE VISCOSITY AND/OR THE PERCENT SOLIDS OF A SUSPENSION IN A CONTAINER.

Electro-mechanical transducer for secondary oil recovery

Abstract: An electromechanical transducer for use in secondary recovery in oil wells which, in effect, produces a dipole-type radiation field of increased magnitude which extends along a single axis perpendicular to the axis of the oil well. This allows the surrounding casing to vibrate in a displacement mode rather than in a circumferential expansion mode, to enable energy coupling to the surrounding oil-producing formation. In specific form of the invention, the transducer includes two resonant beams forced to vibrate at an audio or sonic frequency by piezoelectric element stacks driven by an external electrical power source and transferring energy through additive shear waves to an external body.

Elastic and Piezoelectric Constants of Ba2NaNb5O15

Abstract: The elastic, piezoelectric, and dielectric constants of Ba2NaNb5O15 have been measured. The experimental techniques used involve mostly thickness‐mode measurements made on small plate‐shaped samples of various crystallographic orientations. As reported previously, the z‐cut plate has a thickness longitudinal mode coupling factor of 0.57, which makes this material attractive for application as a high‐frequency longitudinal mode transducer. However, from the measured constants and the theory of piezoelectric plate vibrations, it is determined that no crystallographic orientation other than the z‐cut has properties suitable for ultrasonic transducer applications.

1.75‐GHz ACOUSTIC‐SURFACE‐WAVE TRANSDUCER FABRICATED BY AN ELECTRON BEAM

Abstract: Surface‐acoustic‐wave interdigital transducers operating at 1.75 GHz have been fabricated on y‐cut z‐oriented LiNbO3 and y‐cut x‐oriented quartz substrates by electron‐beam techniques. The transducers consist of 25 pairs of interleaved aluminum ``fingers'' 0.3 μ wide and 0.7 μ apart. Used as a surface acoustic wave delay line, the insertion loss has been measured to be as low as 25 dB with a bandwidth of 70 MHz for 2.2‐μsec delay. The parameters of the equivalent circuit of the transducer have been measured and agree with the theoretical calculation.

A silicon MOS magnetic field transducer of high sensitivity

Abstract: A structure has been devised which converts magnetic flux density change to a change in output current. The structure is essentially a P-channel MOST with the drain diffusion split into two halves. A magnetic field normal to the silicon surface deflects device current towards one half-drain. By operating the MOST in the "pinched-off" mode (V DS > V GS -V T ) the output impedance is made high, so that large output voltage swings may be obtained. A theoretical study of the voltage and current distributions in the MOST channel has given data on the influence of device geometry on sensitivity. Experimental results indicate a linear relationship between output current and magnetic flux density, and an unexplained nonlinear variation of output with device current. Comparison of experimental results with theory indicates a carrier Hall mobility in the channel of 116 cm2/V.s.

Ultrasonic transducer assembly for biological monitoring

Abstract: AN ULTRASONIC TRANSDUCER ASSEMBLY FOR USE WITH A HUMAN OR AN ANIMAL BODY, COMPRISING A FLEXIBLE PRINTED CIRCUIT MEANS HAVING A PRESET CURVATURE, FOR SUPPORTING AN ARRAY OF ULTRASONIC TRANSDUCER UNITS ELECTRICALLY CONNECTED TO THE PRINTED CIRCUIT FOR IRRADIATING A SELECTED SECTION OF A BODY WITH ULTRASONIC ENGERGY AND FOCUSING THE RELATED TRANSMITTED ULTRASONIC ENERGY. THE TRANSDUCER ASSEMBLY IS USABLE FOR BLOOD PRESSURE MONITORING BY PLACEMENT WITH AN INFLATABLE CUFF ABOUT A BODY LIMB FOR DETECTION OF ARTERIAL WALL MOTION INDUCED BY CUFF PRESSURE VARIATIONS.

Signal translating apparatus using surface wave acoustic device

Abstract: A variable transmission apparatus for translating signals between a source and a load comprises a substrate propagative of acoustic surface waves. An input transducer coupled to a surface of the substrate and responsive to applied signals serves to launch acoustic waves. An output transducer is coupled to a portion of the surface spaced from the input transducer and, in response to the launched waves, derives output signals having a delay, relative to the input signals, that corresponds to the spacing between the transducers. Means are included for flexing the substrate to alter the surface wave phase velocity.

High pressure piezoelectric transducer

Abstract: An alternating voltage is applied to the electrodes of a piezoelectric crystal at the frequency of natural vibration of the crystal in the thickness mode which causes the crystal to vibrate in the thickness mode. This vibration is at one-half wavelength resonance. Vibrations from the front surface are transmitted through an epoxy window as an ultrasonic wave. Vibrations off the back surface are reflected from a reflector which is spaced one-quarter wavelength from the crystal. A filler material with negligible reflective qualities, such as neoprene, synthetic or natural rubbers, or the like, is sandwiched between the crystal and the reflective material. The filler also has the properties of compressions so that the crystal will not break or cave in when the transducer is subject to high pressures when submerged in very deep water.

Solid-state digital pressure transducer

Abstract: The solid-state digital transducer represents a new standard in precision pressure transduction for the next generation of airborne sensors. The pressure transducer produces pulse train outputs as a measure of pressure by developing strains in a silicon diaphragm which incorporates piezoresistive sensing elements. These elements are distributed resistance-capacitance (RC) networks which are diffused into a diaphragm surface as the control elements of phase shift oscillators. By this approach, a digital (frequency) signal generated at the source can be transmitted without noise and distance limitations and the need for precision analog to digital conversion is eliminated. The device exhibits advantages in the areas of reliability, accuracy, size and cost over present day analog devices. The solid-state digital pressure transducer is being developed to meet the requirements of supersonic and subsonic air data applications when coupled with a high-performance air data computer. This application requires low hysteresis with repeatability and stability which are the main features of the solid-state pressure transducer. Other possible applications are FM data acquisition systems and industrial robots.

Acoustic logging tool having opposed transducers

Abstract: A logging tool having opposed paired transducers located on opposite sides of the borehole in both the source and the detector and methods for its use. One source transducer expands while the opposed transducer contracts and one detector transducer emits a positive electrical signal in response to inward pressure, while the other emits a negative electrical signal in response to inward pressure. The tool thus exploits flexural waves along a borehole and minimizes interference by the faster-traveling compressional waves.

Force transducer units with multiple sensing elements

Abstract: A transducer unit in which the force or forces to be measured, are divided at a predetermined ratio by the use of at least one piezoelement and at least one idle element, of substantially similar thicknesses and characteristics, which are disposed between the force-transmitting supports.

Sonar scanning mechanism

Abstract: A MARINE SONAR SYSTEM IS DISCLOSED EMPLOYING A SUPPORT MECHANISM FOR AN ACOUSTIC TRANSDUCER CAPABLE OF STABILIZING THE TRANSDUCER FROM THE PITCH AND ROLL MOTION OF SHIP. THE TRANSDUCER IS FREELY SUSPENDED FROM A FRAME. A DRIVE MECHANISM FOR VAYING THE ANGLE OF THE TRANSDUCER INCLUDES TWO RING GEARS MESHED WITH PINION GEARS JOURNALED IN THE FRAME. THE RING GEARS ARE FREE TO ROTATE ABOUT THE PINION GEARS TO ALIGN WITH THE GRAVITY VECTOR. ADDITIONALLY, ROTATION OF TEH PINION GEARS ROTATES THE TRANSDUCER WITHOUT DISTURBING ITS ALIGNMENT WITH THE GRAVITY VECTOR. THE TRANSDUCER CAN BE AIMED TO VARYING WATER DEPTHS BY ROTATION OF THE PINION GEARS. THE PINION GEARS ARE DRIVEN BY AN INTERMEDIATE GEAR MECHANISM MESHED WITH VERTICAL RACK GEARS. THE RACK GEARS ARE SPLIT INTO HALVES SO THAT ONE-HALF CAN REMAIN IN MESH WITH A DRIVE MOTOR WHILE THE ENTIRE FRAME ON WHICH THE TRANSDUCER IS MOUNTED IS ROTATED TO AIM THE TRANSDUCER AT VARIOUS ANGLES. THE SONAR SYSTEM FURTHER INCLUDES MEANS FOR RAISING AND LOWERING THE TRANSDUCER RELATIVE TO THE HULL OF THE SHIP BETWEEN SCANNING AND REST POSITION.

Apparatus for mounting and spacing a signal transducer with respect to a recording medium

Abstract: A device for supporting and controlling the position of a signal transducer with respect to a recording medium. A body of material which exhibits dimensional change in the presence of an electric or magnetic field applied to the material, is utilized as part of the support structure for the transducer and/or the recording medium. The value of the field applied to the material determines the relative spacing of the transducer and recording medium. Servo means, responsive to the relative spacing between the transducer and medium, may be provided for controlling the field, to establish and maintain a desired spaced relation therebetween.

Acoustic-surface-wave filters

Abstract: Two examples of filters using Rayleigh waves, at the frequencies of 25 MHz and 150 MHz, are described. The shape, almost rectangular, of the frequency response is determined by drawing one transducer.