In (3), Rp is the inverse of the maximum conductance in
the loaded transducer. The time response VT ðtÞ could be
computed from the complex frequency response derived
from (2).
Since possible effects from the rectifier devices RÃ
C
have not been considered, expression (2) is valid only
until the first zero-crossing of the spike. This reduces the
application of this driving model to not very narrow
spikes (low-MHz range); moreover it is not very
appropriate for analysing VT when fine details must be
considered. For this reason we proposed another model
in [10], based on an equivalent network integrating the
whole transmitter, for an accurate simulation of driving
responses. It integrates the real effects of all the com-
ponents in Fig. 1 with a version of the Mason–Redwood
circuit for the piezoelectric section of the transmitter.
In order to analyse, with this equivalent network,
possible non-linear influences on the transmitter voltage
VT ðtÞ, we have used the same driving scheme as in [10].
The components involved are of plug-in type and can be
removed for different experiments. As an example of the
magnitude of these influences, Fig. 2 shows the experi-
mental and computed waveforms obtained when the
two rectifier sets RÃ are removed in the driving scheme
C
of Fig. 1. The high-amplitude oscillations of the C-LSh
resonant circuit cause a harmful lengthening of the
spike from typical time-durations when RÃ are present
C
(roughly signed with the shaded zone). This experiment
was made with the driver configuration used for resistive
load in [10], but here loading with a tuned probe of 6
MHz of nominal frequency through a l m long coaxial
cable. In this case, the internal ‘‘real’’ HV step function,
loaded by the probe, descended from 82 to 2 V in 7 ns.