Fabrication and performance of a high-frequency geometrically focussed composite transducer with triangular pillar geometry

A single-element, 40 MHz, 3 mm diameter transducer was fabricated with a geometric focus at 9 mm The transducer was based on a piezo-composite substrate with triangular-shaped composite pillars. The transducer produced pukes with a two-way bandwidth of 55 %. The bandwidth and impedance magnitude were in agreement with that predicted using finite element modeling. A one-way radiation pattern was collected using a needle hydrophone The one-way -3 dB beamwidth at the geometric focus was measured to be 120 pan and the -3 dB depth-of-field was 2.5 mm This is in good agreement to the theoretical predictions of 112.5 μm and 2.4 mm The triangular-pillar composite transducer was then compared to a transducer with square composite pillars. A 12 dB reduction in the amplitude of the secondary resonance was found for the triangular-pillar composite