  A FEM application for the accurate design of composite backing of ultrasonic
transducers is presented. The idea is to obtain the dependence between the
volume ratio of the tungsten powder in an epoxy matrix used as a backing and
the final pulsed RF signal emitted by the backed transducer. An inhomogeneous
material model for the backing was adopted instead of the classic complex
geometrical FEM. The model was developed in Comsol 5.5 using two of its physics
interfaces. The first based on classic FEM or continuous Galerkin for
ultrasonic propagation in the backing and the second based on a discontinuous
Galerkin option for fluid pulsed propagation. In this way it is possible to
avoid the use of an impedance-based model. The calculations for the resulting
bandwidth are good enough as predicted for Desilets for the 1D case by using
the KLM circuital model. We worked in a 2D space, where the transducer face
vibration is far away from the assumed piston-like considered by the
unidimensional KLM model.

Computational Physics