Tunable acoustic resonator for clinical ultrasonic transducers
Patent 5438554 Issued on August 1, 1995. Estimated Expiration Date: February 28, 2014. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
367/140, SIGNAL TRANSDUCERS310/320, Piezoelectric slab having different resonant frequencies at different areas310/334, Acoustic wave type generator or receiver310/336, Nondestructive testing type367/153, Plural transducer array600/447, Electronic array scanning600/459Structure of transducer or probe assembly
A tunable ultrasonic probe includes a body of a first piezoelectric material acoustically coupled in series with a body of a second piezoelectric material. The second piezoelectric material has a Curie temperature that is substantially different than that of the first piezoelectric material. Preferably, the first piezoelectric material is a conventional piezoelectric ceramic, such as lead zirconate titanate, while the second piezoelectric material is a relaxor ferroelectric ceramic, such as lead magnesium niobate. At an operating temperature of the probe, the first piezoelectric material has a fixed polarization. In contrast, the second piezoelectric material has a polarization that is variable relative to the fixed polarization of the first piezoelectric material. A preferred novel arrangement of electrodes electrically couples the bodies in parallel with one another. An oscillating voltage for exciting the acoustic signals in the probe is coupled with the electrodes. The polarization of the second piezoelectric material is variably controlled by a bias voltage coupled with the electrodes. In a preferred embodiment, the bias voltage has a reversible electrical polarity for selecting one resonant frequency from a plurality of resonant frequencies of the probe. In another preferred embodiment, the bias voltage source has a variable voltage level for selecting at least one of a plurality of resonant frequencies of the probe.
Other References
N. Kim, S. J. Jang, and T. R. Shrout; "Relaxor Based Fine Grain Piezoelectric Materials"; Proceedings of the 1990 IEEE International Symposium on Applications of Ferroelectrics; pp. 605-609, 1991
W. Y. Pan, W. Y. Gu, D. J. Taylor and L. E. Cross; "Large Piezoelectric Effect Induced by Direct Current Bias in PMN:PT Relaxor Ferroelectric Ceramics"; Japanese Journal of Applied Physics, vol. 28, No. 4, 1989, pp. 653-661
Thomas R. Shrout and Joseph Fielding, Jr.; "Relaxor Ferroelectric Materials"; 1990 Ultrasonic Symposium Proceedings, vol. 2, IEEE, 1990, pp. 711-720
Sixte de Fraguier, Jean-Francois Gelly, Leon Volnrerman and Olivier Lanuzel; "A Novel Acoustic Design for Dual Frequency Transducers Resulting in Separate Bandpass for Color Flow Mapping (CFM)"
Hiroshi Takeuchi, Hiroshi Masuzawa, and Yukio Ito; "Medical Ultrasonic Probe Using Electrostrictive/Polymer Composite"; 1989 Ultrasonic Symposium Proceedings; IEEE, pp. 705-708
D. J. Taylor, D. Damjanovic, A. S. Bhalla, and L. E. Cross; "Complex Piezoelectric, Elastic, and Dielectric Coefficient of La-Doped 0.93 Pb(Mg1/3 NB2/3)O3 :0.07 PbTiO3 under DC Bias", Ferroelectrics Letters, 1990, vol. 11, pp. 1-9
D. J. Taylor, D. Damjanovic, A. S. Bhalla, and L. E. Cross; "Electric Field Dependence of dh In Lead Magnesium Niobate Lead Titanate Ceramics"; Proceedings of the 1990 IEEE International Symposium on Application of Ferroelectric; pp. 341-345, 1991
Wallace Arden Smith and Bertram A. Auld; "Modeling 1-3 Composite Piezoelectrics: Thickness-Mode Oscillations"; IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 38, No. 1, Jan., 1991, pp. 40-47
R. E. Newnham, D. P. Skinner and L. E. Cross; "Connectivity and Piezoelectric-Pyroelectric Composites"; Mat. Res. Bull. vol. 13, pp. 525-536
M. I. Haller and B. T. Khuri-Yakub; "Micromachined Acoustic Matching Layers"; SPIE, vol. 1733, 1992, pp. 72-77
M. I. Haller and B. T. Khuri-Yakub; "Micromachined Ultrasonic Materials"; 1991 IEEE Ultrasonics Symposium; pp. 403-405
Peder C. Pedersen, Oleh Tretiak, and Ping He; "Impedance-Matching Properties of an Inhomogeneous Matching Layer with Continuously Changing Acoustic Impedance"; 1982 Acoustical Society of America, vol. 72, No. 2, pp. 327-336
Erhard K. Sittig; "Transmission Parameters of Thickness-Driven Piezoelectirc Transducers Arranged in Multilayer Configurations"; IEEE Transactions on Sonics and Ultrasonics, vol. SU-14, No. 4, Oct., 1967, pp. 167-174
Karen Pendergraft and Ronald Piper; "An Exact Solution for a Reflection Coefficient in a medium having an Exponential Impedance profile"; 1993 Acoustical Society of America, vol. 94, No. 1, Jul., 1993, pp. 580-582
Wallace Arden Smith; "New Opportunities in Ultrasonic Transducers Emerging from Innovations in Piezoelectric Materials"; 1992 SPIE International Symposium, Jul. 1992, pp. 1-2
February 28, 2014. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
