Enhanced KLM model for single-fibre piezocomposite transducers

The requirements of our third generation 3D ultrasound computer tomography system (USCT) led to a transducer array design based on single-fibre piezocomposites. The used piezoelectric ceramic fibres exhibit a thickness to diameter ratio of 4/3. This ratio results in a proximity of the dominant axial and lateral vibration resonances. The standard Krimholtz-Leedom-Matthaei (KLM) model considers only one spatial dimension. This limits the validity of the modelled predictions for our application. By adding a coupled transmission line in series to the axial resonator, the standard model can be extended to take additional spatial dimensions into account. Using model parameters from literature resulted in a low model-to-measurement fit. To enhance the prediction accuracy, a brute-force optimisation over four model parameters was conducted. With the optimal parameter set, a fit of 90.3% could finally be achieved. The necessary model parameter changes were found reasonable for the piezocomposite design. With the presented model enhancement it is now possible to consider both dominant vibration modes of our transducers.