User`s guide

6
-
16 Analo
g
Behavioral Modelin
g
GVALUE parts, Modeling Mathematical or Instantaneous
Relationships on page 6-30). The output for each frequency is
then the input times the gain, times the value of the table at that
frequency.
For transient analysis, the voltage is evaluated at each time
point. The output is then the convolution of the past values with
the impulse response of the frequency response. These rules
follow the standard method of using Fourier transforms. We
recommend looking at one or more of the references cited in
Frequency-Domain Device Models
on page 6-35 for more
information.
Note
The table’s frequencies must be in order from
lowest to hi
g
hest. The TABLE part provides one
input and one output.
Example
A device, ELOFILT, is used as a frequency filter. The input to
the frequency response is the voltage at net 10. The output is a
voltage across nets 5 and 0. The table describes a low pass filter
with a response of 1 (0 dB) for frequencies below 5 kilohertz and
a response of 0.001 (-60 dB) for frequencies above 6 kilohertz.
The phase lags linearly with frequency. This is the same as a
constant time delay. The delay is necessary so that the impulse
response is causal. That is, so that the impulse response does not
have any significant components before time zero. The
FTABLE part in Figure 6-5 could be used.
Fi
g
ure 6-5
FTABLE Part
Example