Bilayer ultrasonic transducer having reduced total electrical impedance
First Claim
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1. An ultrasonic transducer comprising:
- an array case made of electrically conductive material electrically connected to ground and comprising four walls which define a rectangular recess, each of said four walls extending perpendicular to a reference plane;
a first planar transducer array of piezoelectric transducer elements arranged inside said recess of said array case at a first elevation and parallel to said reference plane, wherein each piezoelectric transducer element of said first planar transducer array has a front face with a first array front electrode on the surface thereof and a rear face with a first array rear electrode on the surface thereof;
a second planar transducer array of piezoelectric transducer elements arranged inside said recess of said array case at a second elevation less than said first elevation and parallel to said reference plane, wherein each piezoelectric transducer element of said second planar transducer array has a front face with a second array front electrode on the surface thereof and a rear face with a second array rear electrode on the surface thereof;
a multiplicity of electrically conductive traces sandwiched between said first and second planar transducer arrays, each conductive trace being electrically connected to a respective first array front electrode and to a respective second array rear electrode,wherein said first transducer array is poled in a first direction and said second transducer array is poled in a second direction opposite to said first direction, each of said first and second transducer arrays has a thickness equal to one-quarter of an ultrasonic wavelength transmitted by said transducer, and said conductive traces have a thickness less than 0.01 times said ultrasonic wavelength.
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Abstract
An ultrasonic transducer having reduced total electrical impedance is constructed by stacking a plurality of piezoelectric transducer element arrays on top of each other. For a given thickness, the electrical impedance of a multilayer stack of piezoelectric transducer element arrays is a function of the number of layers. If the number of layers equals two, then the electrical impedance of the total stack-up of layers is reduced by a factor of one-quarter relative to the electrical impedance of a single layer of equal thickness. This facilitates matching the overall transducer impedance to that of the connecting cable.
43 Citations
6 Claims
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1. An ultrasonic transducer comprising:
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an array case made of electrically conductive material electrically connected to ground and comprising four walls which define a rectangular recess, each of said four walls extending perpendicular to a reference plane; a first planar transducer array of piezoelectric transducer elements arranged inside said recess of said array case at a first elevation and parallel to said reference plane, wherein each piezoelectric transducer element of said first planar transducer array has a front face with a first array front electrode on the surface thereof and a rear face with a first array rear electrode on the surface thereof; a second planar transducer array of piezoelectric transducer elements arranged inside said recess of said array case at a second elevation less than said first elevation and parallel to said reference plane, wherein each piezoelectric transducer element of said second planar transducer array has a front face with a second array front electrode on the surface thereof and a rear face with a second array rear electrode on the surface thereof; a multiplicity of electrically conductive traces sandwiched between said first and second planar transducer arrays, each conductive trace being electrically connected to a respective first array front electrode and to a respective second array rear electrode, wherein said first transducer array is poled in a first direction and said second transducer array is poled in a second direction opposite to said first direction, each of said first and second transducer arrays has a thickness equal to one-quarter of an ultrasonic wavelength transmitted by said transducer, and said conductive traces have a thickness less than 0.01 times said ultrasonic wavelength. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification