The echo signals of Fig. 5, in water, were obtained by
reflection in a steel target situated in the transition zone
to the transducer far-field. It can be observed that, from
near the voltage level switching on rectifiers, there
C
appears a clear distortion in the positive part of the echo
signal of higher amplitude, in comparison to the alternative result for a lower excitation level. In order to
better display these asymmetric effects, each of the responses in Fig. 5 has been normalised to its maximum
value.