Characterization of high frequency transducers with wire target and hydrophone

In this paper, a wire-target technique was used for lateral beam profile measurements for single-element focused transducer in the very high frequency range (35-60 MHz). Two wire-targets made from 9 cm long tungsten wires with diameters of 8 μm and 20 μm were used as the pulse-echo target to measure the lateral beam profiles at the focal plane of two single-element focused transducers, a spherically focused 40 MHz Panametrics transducer and a lens-focused in-house lithium niobate (LiNbO₃) 60 MHz transducer. For comparison, measurements on the same transducers were performed by three small-aperture hydrophones with geometrical diameters varying from 37 μm to 150 μm. Results obtained with the wire-target technique are comparable to those obtained with small aperture hydrophones in characterizing the lateral radiation patterns of a single-element focused transducer in the high frequency range (35-60 MHz). However, wire-targets may overestimate pulse length. Compared to small-aperture hydrophones, the wire-target technique is simpler and more cost-effective. Its major advantage however is in the frequency range above 100 MHz in which commercial hydrophones are not yet available.