Equivalent lossy redwood circuits for high-frequency piezoelectric array elements

Ultrasonic transducer arrays in medical imaging are typically composed of multiple piezoelectric elements. This research focuses on modeling high-frequency piezoelectric slender bars, along with their front and back matching layers, using 1D and 2D Redwood equivalent circuits. The entire ultrasonic transducer under examination includes an active piezoelectric component (Motorola 3203HD), two front acoustic matching layers (ML#107 and ML#103), and a backing material designed for absorption. The novelty of this work consists in proposing an accurate Lossy 2D Redwood model that accounts for various dissipations, including piezoelectric, dielectric, and mechanical losses, as well as the thickness and width modes and the coupling between them. Additionally, when building our lossy transmission lines, the frequency change of the acoustic attenuation is taken into account. The proposed 2D model is implemented in LTspice software to analyze the effects of the front and back matching layers on the transducer’s electromechanical performance, specifically its electrical impedance. The simulation results align well with existing literature, confirming the validity of the proposed approach. The advantages of the proposed model are its ease of use, simplicity, and, most importantly, its shorter computation time when compared to the numerical models that are frequently used in the literature. The proposed Lossy 2D Redwood model is anticipated to prove useful for modeling comprehensive transducer arrays and analyzing crosstalk phenomena, which will be explored in future work.