Mir Said Seyed-Bolorforosh

Method for making integrated matching layer for ultrasonic transducers

A method of forming an impedance matching layer of an acoustic transducer includes geometrically patterning impedance matching material directly onto a radiating surface of piezoelectric substrate. In one embodiment, the matching layer is deposited onto the piezoelectric substrate and photolithographic techniques are utilized to pattern the matching layer to provide posts tailored to better match the piezoelectric substrate to a medium into which acoustic waves are to be transmitted. A nominal layer of metal between the posts and the piezoelectric substrate improves the attachment of the matching material to the substrate. The nominal layer may be chrome-gold and the matching material may be copper. Typically, the radiating surface is the substrate front surface from which acoustic waves are directed into a medium of interest, e.g., water or human tissue. However, the radiating surface may be the substitute rear surface, with the patterned matching layer providing acoustic matching to a backing layer for absorbing acoustic energy. In another embodiment, matching layers of different acoustic impedances are deposited and patterned on both the front and rear surfaces to provide matching for effective transmission into the medium of interest and into an acoustic absorptive backing medium.

A 2.5 MHz 2D array with Z-axis backing

The design, fabrication and initial testing of a prototype fully /spl lambda//2 sampled, 2500 element 2D phased array is presented. The array utilizes a unique Z-axis electrical conductivity backing layer, to provide both acoustic attenuation and electrical interconnect for the signal channels. The electrical interconnect is designed to be in the acoustic shadow of the transducer elements so as to minimize the foot print of the array. A modular, demountable Pad Grid Array interconnect is used to connect to the backing of the array. Results are presented for measurements of the single element properties of electrical impedance, pulse echo waveform and spectrum, directivity and cross talk.

Acoustic transducer using phase shift interference

A transducer device includes delay sections for creating a phase differential of acoustic waves. The delay sections are spaced apart by sections having an absence of delay. In a preferred embodiment, the phase differential is 180°, so that constructive and destructive interference of pressure waves function occurs to reduce the ringdown time of the transducer device. In the preferred embodiment, the array of delay sections is at the back surface of a piezoelectric element. However, delay sections may be at the front, radiating surface of the piezoelectric element for control of the shape of emitted pulses. Vectorial summation of wave energy cancels unwanted energy that is present as a result of reverberations within the transducer device. Alternative delay structures or multiple delay sections can be used to control the transducer impulse response.

2.5-MHz 2D array with z-axis backing

The design, fabrication and initial characterization of a prototype fully lambda/2 sampled, 2.5 MHz, 50 by 50 element 2D array for cardiac medical imaging applications is presented. The array utilizes a novel Z-axis electrically conductive backing layer to provide both appropriate acoustic attenuation, and an anisotropic electrical interconnect for the individual acoustic elements in the 2D array. A modular, demountable pad grid array (PGA) interconnect is used to connect the backing. The PGA is capable of terminating the full 2500 element array at a spatial pitch of 300 microns. Measurements are presented on the electrical impedance, directivity and cross talk of the 2D array module, as well as the pulse echo properties of the 2D array elements excited through the pad grid array interconnect system. The single element directivity is measured to be 35 degrees, while the nearest neighbor electrical cross talk is measured at minus 42 dB. The pulse echo waveform has a fractional bandwidth of 50%.

Integrated impedance matching layer

Improved design of clinical and industrial ultrasonic transducers requires an impedance matching layer with efficient coupling of acoustic energy between the piezoelectric ceramic and the propagating medium with controlled acoustic properties and ease of manufacturing. Traditional impedance matching layers comprise solid particles surrounded by a polymer matrix. This is prepared separately and then bonded to the piezoelectric layer. In this paper a new technique for making an integrated acoustic impedance matching layer is described. This is made by making a series of shallow grooves at the surface of the bulk piezoelectric ceramic layer. These grooves extend partially into the bulk piezoelectric ceramic. The depth of the grooves determines the thickness of the integrated impedance matching layer. By depositing an electrode that extends into the grooves the electrical potential distribution inside the integrated impedance matching layer is controlled. The integrated impedance matching layer is piezoelectrically inert. The principle of operation for the integrated impedance matching layer is described here. The impulse response for a transducer with the integrated impedance matching layer radiating into water is presented here. The experimental and the simulation results are compared showing a good correlation.