Design of a high-sensitivity wideband ultrasonic transducer with an ultra-high acoustic-impedance backing.

Ultrasonic transducers are the key components for acoustic transmission and reception. High-quality ultrasonic imaging requires both high sensitivity and broad bandwidth. However, the conventional transducer structures face an intrinsic trade-off between sensitivity and bandwidth and therefore rarely achieve both simultaneously. This work presents a transducer design that attains high sensitivity and wide bandwidth concurrently by combining a dual-layer front matching network, a 1-3 piezoelectric composite active layer, and an ultra-high acoustic-impedance backing structure (UHAIBS). The UHAIBS alters the boundary condition of the piezoelectric layer so that most acoustic energy is efficiently utilized. Finite element simulations indicate a sensitivity increase of ≈3.88 dB and a bandwidth expansion from 71.2% to 83.5% relative to a conventional structure. A prototype was fabricated and experimentally characterized; measurements confirm the design's high-sensitivity and wideband behavior and validate imaging performance in a phantom. The proposed design offers a practical route to high-performance ultrasonic transducers for medical imaging and industrial nondestructive testing.