Design and fabrication of a 40-MHz annular array transducer

Abstract

This paper investigates the feasibility of fabricating a 5-ring, focused annular array transducer operating at 40 MHz. The active piezoelectric material of the transducer was a 9-μm thick polyvinylidene fluoride (PVDF) film. One side of the PVDF was metallized with gold and forms the ground plane of the transducer. The array pattern of the transducer and electrical traces to each annulus were formed on a copper-clad polyimide film. The PVDF and polyimide were bonded with a thin layer of epoxy, pressed into a spherically curved shape, and then back filled with epoxy. A 5-ring transducer with equal area elements and 100 μm kerfs between annuli was fabricated and tested. The transducer had a total aperture of 6 mm and a geometric focus of 12 mm. The pulse/echo response from a quartz plate located at the geometric focus, two-way insertion loss (IL), complex impedance, electrical cross-talk, and lateral beamwidth were all measured for each annulus. The complex impedance data from each element were used to perform electrical matching and the measurements were repeated. After impedance matching, f c ≈ 36 MHz and BWs ranged from 31 to 39%. The ILs for the matched annuli ranged from −28 to −38 dB.

High-Frequency Ultrasonic Imaging of the Anterior Segment Using an Annular Array Transducer

“…The array was fitted into a UHF connector to provide mechanical protection and electrical shielding ( Figure 2). Fabrication is described in greater detail by Ketterling (2005). 21 We developed a LabVIEW program (National Instruments, Austin, TX) to control the components of the PC-based scanning system, including the pulser, the switching unit, receive channels, and the three orthogonal linear motion stages used for scanning.…”

“…However, by adding appropriate time delays to the digitized echo data from each send/receive ring pair and then summing, synthetic focusing can be achieved at any axial depth. 21 We produced composite synthetically focused images by merging synthetically focused data over a series of 41 focal zones of increasing depth. Acquisition time for a single synthetically focused image was approximately 40 seconds.…”

“…Annular arrays can be fabricated with no curvature (i.e., flat) 18-19 , with a spherical lens 20 , or with a spherical geometry [21][22] . While the principle of dynamic focusing is the same for all, spherically curved devices are advantageous compared to flat arrays because fewer elements are required to achieve the same improvement in DOF.…”

40-MHz annular array imaging of mouse embryos

“…Details of the array fabrication and characterization have been reported previously (Ketterling et al 2005). Briefly, an equal area, five-element annular array pattern was etched into a copper clad polyimide membrane using standard printed circuit board techniques.…”

“…Previously, we described the development of a 5-element, 40-MHz PVDF annular array transducer for UBM imaging (Ketterling et al 2005). The operational capability of this transducer was recently verified using an offline synthetic array-focusing method (Ketterling et al 2006).…”