Equivalent Circuit Of Transducer Research Articles

Loudspeaker virtualization–Part I: Digital modeling and implementation of the nonlinear transducer equivalent circuit

This manuscript, the first of a two-part series, presents a methodology for efficiently implementing an equivalent circuit of nonlinear loudspeakers in the discrete-time domain. This is a crucial step that will allow us to design new algorithms for loudspeaker virtualization in part II of this series. The presented implementation, in fact, is based on Wave Digital Filter (WDF) principles, which lead to a fully explicit model, in the sense that no iterative solvers are needed to compute the output signal. The proposed WDF is highly efficient and modular, since the reference circuit is modeled as a computable interconnection of input-output processing blocks. The accuracy of the implementation is confirmed by comparing it to a ground-truth SPICE simulation of the reference circuit and to measurements on real loudspeakers. This confirms that the proposed Wave Digital modeling approach can be reliably used for the rapid simulation of the transduction behavior of a loudspeaker (within the frequency limits of validity of the equivalent circuit), and can be employed to develop the digital preprocessing method for loudspeaker virtualization described in the second manuscript of this two-part series.

Theory of Series Inductance Matching to Transducer at Premechanical Resonance Zone in Ultrasonic Vibration Cutting

In order to obtain large vibration amplitude in ultrasonic vibration cutting, the transducer demands an additional inductance to match its native capacitance. The objective of this paper is to determine the optimum oscillation frequency of the resonant tank constructed using additional inductance and the transducer's native capacitance. By analyzing the transducer impedance matching on the impedance circle deduced from the transducer equivalent circuit model, the optimum oscillation frequency is found to be not equal to the transducer mechanical resonance frequency, but below it. Frequencies near the optimum oscillation frequency are referred to as the optimum premechanical resonance zone. Consequently, the Theory of Ultrasonic Transducer Impedance Matching at Premechanical Resonance Zone is proposed. Comparative experiments are conducted at different frequency zones. The results reveal that when the transducer is excited at the premechanical resonance zone, the vibration amplitude increases and the excitation voltage signal is the desired sine wave, compared to that when excited at the mechanical resonance frequency and the postmechanical resonance zone. The experimental results confirm the feasibility of this proposed theory.

Study on the effects of temperature on the equivalent circuit parameters of ultrasonic grinding transducer

The variation characteristics of the ultrasonic grinding transducer equivalent circuit parameters under the effect of temperature were studied in this paper. An ultrasonic grinding transducer equivalent circuit model was established. Then an experimental platform was set up to test the variation regularity of the ultrasonic grinding transducer equivalent circuit parameters at different temperatures. The results have important guiding significance for the control and process design of the ultrasonic grinding.

Estimation of vibration amplitudes for resonating sensors immersed in liquids

For a lot of vibrating sensors operating in liquids, it is difficult to accurately model the displacement amplitude exerted at the interface to the liquid. The presented approach provides an estimate by relating the power in the radiation resistance of the transducer's equivalent circuit to the acoustic radiation into the liquid. The only prerequisite for the application of the method is that a dominantly shear or normally polarized mode is present and that an effective area characterizing interaction between transducer and liquid can be estimated.

Determining equivalent circuit parameters for low figure of merit transducers

A new analytical technique for deriving transducer equivalent circuit parameters from complex electrical admittance data is presented. The new method handles low figure of merit transducers (those having weak coupling and/or low Qm), but does not require phasor subtraction or similar geometrical manipulations of the admittance loop. Four parameters of the unloaded, single degree-of-freedom equivalent circuit are extracted from a simple analysis of the capacitance curve, B(ω)/ω, and one additional parameter is obtained from the dissipation curve, G(ω)/B(ω). This technique simplifies the evaluation of developmental transducers, particularly those using marginal or weakly polarized materials.

High-frequency membrane hydrophone

A membrane hydrophone with a 37-/spl mu/m diameter spot poled electrode has been fabricated on a 4-/spl mu/m-thick film of the piezoelectric copolymer, polyvinylidene fluoride trifluoroethylene (PVDF-TrFE), and initially characterized. The hydrophone has an effective spot size of less than 100 /spl mu/m, an on-membrane +7-dB gain buffer amplifier, and a -3-dB bandwidth of 150 MHz. The acoustic properties of the hydrophone were investigated with a transducer equivalent circuit model, the electric fringe fields due to poling were characterized with a finite difference electrostatic field model, and the effective spot diameters 2a/sub 3/ and 2a/sub 6/ were estimated. Measurements on the bandwidth, effective spot size, and sensitivity are presented. This hydrophone appears suitable for the characterization of both the frequency and spatial parameters of high-frequency transducers such as intravascular ultrasound (IVUS) catheter transducers operating in the 10-40 MHz range.

On the power limitations of sonic transducers

When the mechanical quality factor Q of a transducer is less than the optimum value, the maximum power output of the transducer at resonance is electric- (or magnetic-) field-limited. When Q is greater than this optimum value, the transducer power is stress-limited. Traditional estimates of the field and stress limits and of the optimum Q, based on a simple equivalent circuit, are often too high for the field limit and too low for the stress limit and the optimum Q. Consideration is given to two extra compliance elements that are useful in flextensional transducer models and in representing glue-joint and stress-bias-rod compliances that occur in practical transducer configurations. When these compliances are included in the transducer equivalent circuit, the effect is to introduce a scale factor α (so that αQ is substituted for Q in the expressions for the power limits) and a second parameter β whose practical effect is less important. The result is that the field limit is reduced by the factor α while the stress limit is increased by approximately 1/α. At the same time, the optimum value of Q is also increased by approximately 1/α, but the maximum power (at the optimum Q) is little changed. An illustration of this effect is given by a lead zirconate titanate (PZT) barrel-stave flextensional transducer with α=0.34 and β=0.53.

Computerized measurement and analysis of sonar transducer equivalent circuit parameters

Measurements of the electrical and mechanical properties of transducers are of importance in both their design and service in their evaluation. Following the formalism of Hunt [Electroacoustics (Acoustical Society of America, New York, 1982)], these properties can be determined by accurate measurements of complex impedance or admittance made throughout the frequency range of interest. Manual collection of the necessary data is tedious and particularly error prone for transducers with sharp resonances. A computer‐controlled system, using an H‐P 85, will be described which automatically acquires and plots the electrical data and calculates the equivalent electrical circuit parameters, coupling constants, and efficiencies. Sample data will be presented for piezoelectric and magnetostrictive transducers. [Work supported by ONR and the NPS Foundation Research Program.]

Computerized Measurement, Display, and Analysis of Sonar Transducer Equivalent Circuit Parameters

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The features of disc shape piezoelectric ceramic transducer equivalent circuit : Kazys, R., Mazák, E., 28 (April 1973) 208–214

Excess volumes, speeds of sound and viscosities were measured for binary mixtures of n-butylamine (NBA) with methyl acetate (MA), ethyl acetate (EA), butyl acetate (BA) and isoamyl acetate (IAA) at 303.15 K over the entire range of composition. Isentropic compressibilities were computed from speed of sound and density data. Densities were obtained from experimental excess volume data in case mixtures. Speeds of sound were evaluated using Jacobson free length theory (FLT) and Schaaffs collision factor theory (CFT). The viscosity data were analyzed on the basis of corresponding states approach and Grunberg and Nissan treatment. The experimental results on excess volume, deviation in isentropic compressibility and in viscosity were discussed in terms of molecular interactions between unlike molecules. A Redlich–Kister type equation was used to fit the experimental data on excess volume, deviations in compressibility and viscosity.

Development of an Underwater Acoustics Laboratory Course

An underwater acoustics laboratory course has been instituted at the University of Miami using a natural body of water as the experimental medium. The experiments are conducted in Bear Cut, which connects Biscayne Bay to the Straits of Florida. The 600-ft acoustic range from the Institute of Marine Sciences pier to an instrument tower in Bear Cut is an almost flat channel with an average depth of about 13 ft. The majority of the equipment employed by the students consisted of piezoelectric projectors and hydrophones, and standard electronic laboratory apparatus such as oscillators, oscilloscopes, power amplifiers, filters, etc. The sequence of the experiments were planned for equipment familiarization and results needed for future tests. During the initial offering of this course in the Spring 1970 semester, experiments were conducted on the measurement of a piezoelectric transducer equivalent circuit, ambient-noise spectrum, spreading loss for several distances, reciprocity calibration, and waveguide effect. For the next offering, additional experiments are planned on arrays including shading and electrical steering, pulse modulation transmission, reflection, sound-velocity measurement, and longer range propagation. The laboratory's facilities are also available for student research.

Determination of the Parameters of a Piezoelectric Transducer from the Decay of Resonant Vibrations

The usual method of determining the RLC parameters of the equivalent circuit of a transducer involves the measurement of admittance or impedance over a range of frequencies near resonance. An alternative method is described here. The transducer is first excited in mechanical resonance by applying an electrical signal; the excitation is then removed and the electrical signal produced by the transducer as the mechanical vibrations decay is observed by using an oscilloscope. Under certain conditions the parameters of the transducer equivalent circuit may be determined rapidly from measurements of the initial amplitude of the electrical signal and the rate at which it decays. The theory of the method is described and used to determine its limitations; the method is particularly suited to rapid measurements on transducers of reasonably low coupling coefficient (less than about 0.4) and reasonably large Q (100 or more). A simple experimental system suitable for measurements to an accuracy of ±10% is discussed and investigations on a barium titanate transducer resonating in a bar mode are described in some detail; the parameters obtained using the decay method compare favorably with those obtained using the conventional admittance method.

Multiple-Reflection-Type Quartz Delay Lines

The performance characteristics, such as time delay, spurious response levels and bandwidth, of multiple-reflection-type delay lines are discussed. State of the art performance is indicated, and efforts to improve these characteristics are described. The time delay is determined by the path length of a given design and size limitations on the fused-quartz blanks. Multiple symmetry designs are derived from regular polygons by rotating facets to achieve long path lengths. Typical designs are presented, and the delays that can be achieved in readily available blanks of fused quartz are indicated. Spurious responses result from diffraction at the transducer and subsequent reflecting facets, and from reflections at the transducers. “Creation angle” spurious responses characterize multiple symmetry type designs, resulting in the use of simpler designs for many critical applications. Aperturization techniques may be employed to control the size of the reflecting facets, and hence to control certain diffraction effects. The delay-line bandwidth is a function of the transducer resonant frequency, bonding techniques and delay medium characteristics. The dependence of bandwidth on bonding parameters is discussed in terms of the transducer equivalent circuit. Medium losses increase with frequency, and limit the attainable bandwidth for long delays. The ultimate performance capabilities of multiple reflection type delay lines using materials and techniques currently available are considered. Limitations imposed on the time-bandwidth product and dynamic range are discussed. Practical upper limits are considered in terms of figures of merit for communications and radar applications.