Showing papers on "Transducer published in 1985"

Computer-steered microphone arrays for sound transduction in large rooms

Abstract: The quality of sound pickup in large rooms—such as auditoria, conference rooms, or classrooms—is impaired by reverberation and interfering noise sources. These degradations can be minimized by a transducer system that discriminates against sound arrivals from all directions except for that of the desired source. A two‐dimensional array of microphones can be electronically beam steered to accomplish this directivity. This report gives the theory, design, and implementation of a microprocessor system for automatically steering a two‐dimensional microphone array. The signal‐seeking transducer system is implemented as a dual‐beam, “track‐while‐scan” array. It utilizes signal properties to distinguish between desired speech sources and interfering noise. The complete automatic system has been tested in anechoic and medium‐sized auditorium environments, and its performance is discussed.

Piezoelectric Composite Materials for Ultrasonic Transducer Applications. Part I: Resonant Modes of Vibration of PZT Rod-Polymer Composites

Abstract: Abstmcr-The objective of the present work was to gain a deeper mensions of the transducer are much smaller than the understanding of the behavior of lead zirconate titanate (PZT) polymer composites for applications such as ultrasonic medical diagnosis in the megahertz frequency range. These composites were originally developed for low-frequency hydrophone applications. The PZT rod-polymer composites have been prepared with five to 30 volume percent PZT using 0.28 mm and 0.45 mm rods. In a disc of PZT rod-polymer composite material, there are three principal types of resonance: the planar mode, the thickness mode, and various lateral modes caused by the regular periodicity of the PZT rod in the composite. These resonance modes have been studied with the following techniques: 1) electrical impedance measurement as a function of frequency and 2) laser probe dilatometry of the dynamic displacement as a function of frequency and position in the composite lattice. The observed resonance behavior is found to be a result of lateral interactions in the composite through the epoxy medium. The effect of temperature on the electromechanical properties of the composite has also been investigated. Implications of these results for optimizing the design of ultrasonic transducers are discussed.

Apparatus for examining and localizing tumors using ultra sounds, comprising a device for localized hyperthermia treatment

Abstract: A hyperthermia treatment apparatus combining a generator of a focused ultrasonic beam comprising a main high frequency electric wave emitter and a main piezoelectric transducer whose active surface is focusing, with an echography device comprising an auxiliary high frequency electric pulse generator associated with an auxiliary piezoelectric transducer and means for causing the zone to be treated to be swept by the ultrasonic examination beam generated by said auxiliary transducer; and with switching and adjustment means for causing, during a main treatment and checking operating mode, emission of said focused beam by said main transducer energized by said main emitter during periodic time intervals separated by shorter time intervals during which the emission of the examination beam and the formation of echographic images are effected.

Broadband multi-resonant longitudinal vibrator transducer

Abstract: A broadband longitudinal vibrator transducer having a laminar head mass section including at least three layers coupled to electromechanical transducer elements. The head section includes a forward head mass, a compliant member abutting the forward head mass and a rear head mass abutting both the compliant member and the transducer elements. The compliant member allows the head mass section to mechanically resonate in at least two frequencies expanding the bandwidth of the transducer. The compliant member can be an active transducer element.

Shear mode transducer for drop-on-demand liquid ejector

Abstract: A single piezoelectric transducer is used to drive an array of drop-on-demand ink jet ejectors. This is accomplished by utilizing a plurality of electrodes which divide the piezoelectric transducer into discrete, deformable sections, each section corresponding to an ejector.

Excitation conditions of flexural traveling waves for a reversible ultrasonic linear motor

Abstract: This paper presents a theory and experiments on a reversible ultrasonic linear motor, consisting of a thin beam, two ultrasonic transducers, and a slider. The slider rides upon the crests of transverse traveling flexure waves propagating down the beam from one transducer to the other.

Variable frequency gas-bubble-manipulating apparatus and method

Abstract: A system for detecting gas bubbles in a specimen utilizes a transducer which produces pulses, illustratively of ultrasonic acoustic energy, having predetermined frequency characteristics. A first pulse has an increasing frequency with time, and a second pulse has a decreasing frequency with time. Imaging arrangements, which may be formed of ultrasonic transducers, produce images of the region within the specimen after exposure to each such pulse. In one embodiment, a growth transducer array is utilized for dramatically increasing the size of the bubbles, which array is formed of a plurality of transducers which are moved with respect to the specimen and which have respective frequency characteristics over different frequency ranges. Thus, bubble radius is successively increased as each bubble is exposed to the acoustic energy from each such transducer within the growth transducer array. The present invention can be used to reduce the cavitation threshold of bubbles, particularly in the vicinity of tumors, or to increase the temperature in the bubble-containing region.

Communication system and method

Abstract: The beamed radiation received by each remote location may also be converted by a radiant electrical energy cell (31) thereat to electrical energy which may be immediately used to power a transmitter (38) and energise a transducer thereat and/or to charge a battery at the remote location for energising such a transmitter and one or more transducers.

Piezoelectric Composite Materials for Ultrasonic Transducer Applications. Part II: Evaluation of Ultrasonic Medical Applications

Abstract: Abstmct-The electro-acoustic properties of Lead zirconate titanate (PZT) rod-polymer composites relevant for ultrasonic transducer applications are reported. Acoustic impedance of the composite materials was measured by three different techniques in the frequency range 0.33.5 MHz. Dependence of the acoustic impedance as a function of volume fraction of PZT and frequency was also modeled theoretically. Time-delay spectrometry was employed to calibrate the free-field transmitting and receiving voltage responses of the composite materials. The acoustic impedance of the composite materials was in the range of 3-10 M rayl. The figure of merit in the receiving mode of composite materials was three times that of PZT. The figure of merit for a 20percent PZT composite (2 = 7.3 M rayl) was further enhanced by 50 percent using a single-layer impedance transformer of lucite (2 =3.3 M rayl). These composite materials were molded into curved shapes by simple thermal process to fabricate focused transducers. The axial and lateral beam profiles of focused composite transducers are presented.

Probe for medical application

Abstract: A medical probe having at least one transducer or electrode for registering or influencing tissue activities is disclosed. The probe comprises a substrate having a supporting surface and a cover layer which, together, form a chamber bounded on one side by the supporting surface and on an opposed side by a wall of the cover layer. The electrode or transducer is carried on the supporting surface of the substrate. An aperture in the wall of the cover layer provides communication between the exterior of the probe and the chamber. The probe is extremely accurate and selective, and extraneous signals which made prior art probes inaccurate do not detract from the accuracy of probes according to the instant invention.

The Natural Single-Phase Unidirectional Transducer: A New Low-Loss SAW Transducer

Abstract: This paper describes a completely new design approach for low-loss SAW transducers and components. This new approach utilizes special unconventional asymmetric crystal orientations. On these new orientations, which exist on conventional piezoelectric cryslals, simple single-level uniform twoelectrodes-per-wavelength transducers can exhibit a unidirectional response. In contrast to low-loss three-phase transducers, air-gap crossovers are not required and all electrode and gap widths are A/4. These new low-loss SAW transducers can thus be easily fabricated at high frequencies. The principle of operation of these new Natural Single-phase Unidirectional Transducers (NSPU DTs) is described. Experimental results for test structures are presented which confirm the existence of NSPUDT orientations on both quartz and LiNbO These results are compared with theoretical predic?fons of a newly developed Coupling-Of-Modes (COM) analysis for these devices. Agreement between experiment and theory is shown to be excellent.

Apparatus and method for generating and directing ultrasound

Abstract: @ The invention is concerned with generating and directing ultrasound over predetermined regions of a body, such as a programmed sequence of target points. A plurality of side-by-side tapered piezoelectric transducer elements (100-1 to 100-n) are provided. Means (170) are provided for energizing the transducer elements with electrical energy having a variable frequency. The frequency of the electrical energy is varied to change the direction of the ultrasound produced by the transducer elements. In the preferred embodiment of the invention, a processor (150) is responsive to a coordinate of an input target point for controlling the variation of frequency. In one form of the invention, means (180) are provided for varying the relative phases of the electrical energy applied to the transducer elements. In this form of the invention, the processor means is also responsive to at least another coordinate of the input target pointfor controlling the variation of the relative phases. In another form of the invention, means (580) are provided for selectively enabling at least one of the transducer elements. In this embodiment, each of the transducer elements has an associated focusing lens, and the processor is responsive to a coordinate of the input target point for controlling the selective enablement.

Touch control system for controllable apparatus

Abstract: A system for recognizing touch positions along an axis on a surface associated with a touch control apparatus comprises a substrate having a surface capable of propagating surface acoustic waves and so characterized that a touch on that surface causes a perturbation of a surface wave passing through the region of touch. An input surface wave transducer coupled to the substrate surface launches a burst of surface waves on the surface. An output surface wave transducer coupled to the substrate detects received surface waves. Wave redirecting gratings derive wave components from the launched wave and redirect them across the substrate surface to the output transducer. The wave components are caused to traverse the axis along a progression of paths associated with different touch positions along the axis. Circuitry coupled to the input and output transducers initiates surface wave bursts across the substrate surface and detects touch-induced perturbations of the received waves indicative of the location of a touch along the axis.

Phased array acoustic imaging system

Abstract: A phased array acoustic imaging system including an array of electromechanical transducers, a dedicated signal processing channel for each transducer and electronic control and delay circuits for them, transmits to and receives ultrasonic energy from a body in a controlled, steered and focused fashion. The electronic delay circuits use a unique cyclically symmetrical arrangement of identical delay cells, each with an electronically variable delay element and each dedicated to a receive signal derived from at least one transducer, to form a summing delay line. The individual delay cells are switched under microprocessor control for efficient combined linear-sector scanning or linear or sector scanning alone. The system includes means to achieve dynamic focusing and dynamic apodization in conjunction with the delay cell architecture.

Transducer-Shadow Effects on Turbulence Spectra Measured by Sonic Anemometers

Abstract: We show that the horizontal turbulent velocity components measured by the common sonic anemometer array can suffer attenuation and crosstalk as a result of the flow blockage caused by the acoustic transducer assemblies. Using an analytical model of this “transducer-shadow effect”, flow-blockage data from test arrays, and a simple linear model of the fluctuating response, we show the nature of the distortion in the measured velocity spectra. We suggest that rather than correct for the shadow effect, which ran be quite significant for horizontal velocity spectra and stress cospectra, it would be preferable to minimize it through design. There is encouraging evidence that the Kaijo-Denki transducer design produces much less shadow effect than the conventional (right circular cylinder) shape.

Infrared fluorescence ‘‘decay‐time’’ temperature sensor

Abstract: The principle of the change in the ‘‘decay time’’ of the fluorescence of a small sample of neodymium in a glass matrix, excited by infrared radiation from a high‐power light emitting diode has been used in the construction of a fiber‐optic temperature sensor. Such a device is an inexpensive transducer and has demonstrated a fiber‐optic sensor not requiring referencing to the intensity of the exciting radiation.

Surface-area pressure transducer and line-selection circuit for use therewith

Abstract: A surface-area-pressure transducer comprises at least one pair of electrode layers each including a plurality of electrically-conductive elements, the elements of one layer extending in spaced, crossing relationship to the elements of the other layer; and a compressively-deformable dielectric layer composed of fibers interposed between the two electrode layers to define therewith an array of capacitors whose capacitances are changed by the compression of the dielectric layer when subjected to pressure. Also described is a line-selector circuit for individually selecting each capacitor for measurement without electrical cross-talk from the other capacitors.

A theoretical study of nonlinear effects with focused ultrasound in tissues: an "acoustic bragg peak".

Abstract: This is a theoretical study of the absorbed power density that arises when a focused ultrasound beam is absorbed in a tissue-like medium. The specific application is selective tissue heating for cancer hyperthermia. Results are expressed in terms of an enhancement ratio which describes the fractional gain in absorbed power density when nonlinear effects are taken into account relative to the absorbed power density that results when only linear effects are considered. Starting from a standard configuration in which the transducer has a (Gaussian) diameter of 0.12 m, a radius of curvature of 0.16 m and an operating frequency of 1 MHz a numerical sensitivity analysis is performed in which transducer and tissue parameters are varied one at a time. Enhancement ratios are invariably greater than unity, often being in the range of 1.5-2 for regions near the focus of the beam. The prediction is that nonlinear effects will probably be useful in selectively increasing the temperature rise in the focal region of a focused applicator.

Heart and breathing alarm monitor

Abstract: A device for sensing heart and breathing rates in a single transducer and having electronic and filtering circuits to process the electrical signal generated by the transducer. The transducer is an electromagnetic sensor constructed to enhance sensitivity in the vertical direction of vibration produced on a conventional bed by the action of patient's heart beat and breathing functions and achieves sufficient sensitivity with no physical coupling between the patient resting in bed and the sensor placed on the bed away from the patient. The electronic circuits integrates the electrical energy generated by the sensor that pertains to cardiac and breathing informations and sets off an alarm when pre-set circuits of these functions have been surpassed. The device has applications in monitoring SID Syndrome and non-ambulatory patients.

Method and apparatus for pressure transducer calibration and simulation

Abstract: A method and apparatus for verifying the calibration of a pressure transducer in a pressure monitoring system and for isolating defective electrical components of the monitoring system. The apparatus includes a manually operable pressure cylinder for generating a known test pressure, a pressure calibration circuit coupled to the known test pressure for displaying on the device a calibrated output indicating the level of the known pressure, and a bypass pressure transducer also coupled to the known test pressure for transforming it into an electrical output signal to replace the transducer in the monitoring system as the source of electronically derived readable output in the monitoring system. The substitute pressure transducer includes a temperature compensation circuit and a semiconductor pressure diaphragm with a piezoresistive strain gauge formed thereon. One side of the diaphragm is coupled to the known test pressure and the other side thereof is referenced to atmosphere. The method and device disclosed have particular application in the medical arts to verify the calibration of and test the pressure transducer and cooperating electronic equipment in a direct patient blood pressure monitoring system.

Spectral analysis of echoes for backscattering coefficient measurement

Abstract: This paper describes spectral analyses of echoes scattered by a random medium and a plane reflector by using mathematical expressions of echoes which have been proposed by us before [M. Ueda and H. Ichikawa, J. Acoust. Soc. Am. 70, 1768–1775 (1981): 75, 1012 (1984)]. It becomes possible to express the spectrum of echoes scattered by the random medium in terms of a backscattering coefficient of the random medium and a velocity potential of an ultrasonic transducer. The expressions hold for any sound field if a correlation length of the random medium is much smaller than a beamwidth and a radius of the transducer. Then the spectrum of the echo scattered by the plane reflector is expressed in terms of a directivity of the transducer. By using a ratio of the two spectrums an expression which gives the backscattering coefficient of the random medium is formulated. It works in a farfield of a flat circular transducer and at a focal plane of a concave one. It is shown that our formula contains those cases which have been proposed so far as the extreme cases of the conditions. Finally, the backscattering coefficients of sponges are measured with several transducers. The results show that our formula gives the coefficients regardless of the transducer geometry.

Transducer for detecting apnea

Abstract: A transducer element particularly adapted for use in an apnea detection system is formed of resilient conductive material having an electrical impedance which varies in response to breathing movement of an infant. A control detects the varying impedance and generates an alarm signal whenever variations caused by breathing movements fall below a predetermined level.

High pressure capacitive transducer

Abstract: A high pressure capacitive transducer includes a capacitive pressure transducer having an insulating diaphragm, and a high pressure fitting for housing the transducer. The high pressure fitting includes a flexible metal diaphragm bonded to the fitting, with the metal diaphragm in engagement with the insulating diaphragm. The metal diaphragm may be boned to the fitting around the periphery of the metal diaphragm to block the high pressure fluid from the transducer. The insulating diaphragm may be relatively thick, such as one-twentieth, one-tenth, or one-fifth of an inch thick, for example.

Saw transition detector for PSK signals

Abstract: A phase transition detector for PSK signals which utilizes a dual channel SAW differential delay line to achieve a required delay. Each channel or path of the SAW device comprises an input and an output transducer. The two channels provide a predetermined differential delay (T) inasmuch as they are of different lengths. A PSK input signal is delivered to a power splitter, with the output therefrom coupled to the pair of input transducers of the SAW device. The output transducers are coupled to a multiplier which serves to detect phase transitions in the input PSK signal. The multiplier output is coupled to an output terminal via a low pass filter which provides harmonic repression. In another embodiment a SAW device comprises a bank of dual channel differential delay lines with each dual channel set to a different predetermined delay (T) so that a plurality of PSK signals of different chip rates can be separated out and detected. The PSK input signals are delivered to a power splitter, with the output therefrom coupled to a pair of input transducers of the SAW device. Output transducers are spaced predetermined distances from one or the other of said input transducers. Parallel sets of multipliers and low pass filters are coupled to predetermined SAW output transducers. Each multiplier serves to detect the phase transitions in one, and only one, PSK input signal. The input transducer(s) can be placed near the center of the SAW device, with the output transducers placed on the same, or either, side of the input transducer(s).

Control yoke apparatus for computerized aircraft simulation

Abstract: An aircraft control yoke apparatus includes an inexpensive mechanism for manipulating a two axis variable transducer and is especially adaptable for use with microcomputers. The apparatus includes a control wheel attached at one end to a shaft which is in turn supported by a linear bearing. The linear bearing permits the shaft to rotate and simultaneously move back and forth. A crank mechanism is attached to the other end of the shaft and serves to amplify the rotational movement of the steering wheel. A resilient, elastic material like natural isoprene rubber connects the crank to a two axis variable transducer. The elastic material causes the two axis transducer to follow the motion of the rotational and back and forth movement of the steering wheel. A return-to-center mechanism causes the wheel to return to a neutral position when no force is applied to it. A very life-like simulation of airplane flight is achieved with a minimum of expense and a high degree of realism.

Sports scoring device including a flexible prezoelectric layer resilient layer

Abstract: Disclosed is a device for generating an analog output signal indicative of an impact to a transducer. The transducer may be mounted on protective equipment utilized in various martial arts fields, such as protective vests and the like or can be mounted on training equipment, such as a heavy bag, striking pad, etc. In a preferred embodiment the transducer is a piezoelectrical signal which is indicative of the amount of deformation. By placing the piezoelectric film on top of a deformable material, in a preferred embodiment sandwiching it in the deformable material, impacts to the deformable material will strain the piezoelectric film generating the signal output. In a further embodiment of the present invention, the piezoelectric transducer is mounted on a target pad and provides an analog output indicative of the characteristics of an object impacting the target pad. For use in the martial arts, the transducer may be connected to a transmitter and remote receiver for providing an indication of the impact at a remote location.

Shear wave acoustic logging system

Abstract: Acoustic well logging method and system employing a bender-type transducer as a point source of an acoustic shear wave. The bender-type transducer includes opposed unrestricted planar surfaces mounted within a liquid filled compartment within the tool. The unrestricted surfaces of the transducer are spaced longitudinally along the axis of the tool and exposed to the coupling liquid. One or more bender-type transducers may also be employed as acoustic receivers in the tools. The active surfaces of the receiving transducers are oriented in substantially the same direction as the active surfaces of the transmitting transducer.

Implant and control apparatus and method employing at least one tuning fork

Abstract: The apparatus and method are utilized in controlling an implanted device, such as a cardiac pacer, by use of acoustic vibrations generated by a tuning fork. These vibrations are applied externally to the skin overlying the implanted device and are sensed by a transducer within the implanted device. The transducer generates an electrical signal of a frequency correlated to the tuning fork frequency. An amplifier and tuned filter are utilized to detect predetermined frequencies within the electrical signals produced by the transducer and to direct the processed signals to a programmable electronic device for control of the implanted device.

Linear position transducer and signal processor

Abstract: Disclosed are a transducer for converting linear motion of a core into a proportional change in inductance by means of skin effect, and bridge processing circuitry for stable conversion of changing inductance into a proportional voltage.