Modeling of received signals from finite reflectors in pulse-echo ultrasound

The spectrum of the output signal from a pulse-echo system is modeled, calculated and experimentally verified for planar, specular reflectors of finite size, placed in a homogeneous medium. As the primary dependence is on the angular orientation of the reflector, relative to the acoustic axis of the transducer, the spectrum is referred to as the Angle-dependent Spectral Distortion for a Finite Planar interface, or the FP-ASD. The FP-ASD function is evaluated through numerical modeling, based on realistic transducer geometries, and through experiments. The modeling utilizes angular spectrum decomposition of the transmitted field for each temporal frequency of interest, followed by diffraction, in the form of k-space convolution, of each plane wave in the transmitted field with an aperture function which is defined by the geometry of the finite reflector. Finally, the acoustic field is propagated to the receiver and integrated to form the receiver output signal. The experimentally obtained FP-ASD functions, when normalized by the transducer´s frequency response, compare well with the corresponding numerical results