User`s guide

6
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38 Analo
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Behavioral Modelin
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The DELAY attribute increases the group delay of the
frequency table by the specified amount. The delay term is
particularly useful when an EFREQ or GFREQ device generates
a non-causality warning message during a transient analysis.
The warning message issues a delay value that can be assigned
to the symbol’s DELAY attribute for subsequent runs, without
otherwise altering the table.
The output of the device depends on the analysis being done. For
DC and bias point, the output is simply the zero frequency
magnitude times the value of EXPR. For AC analysis, EXPR is
linearized around the bias point (similar to EVALUE and
GVALUE parts). The output for each frequency is then the input
times the gain of EXPR times the value of the table at that
frequency. For transient analysis, the value of EXPR is
evaluated at each time point. The output is then the convolution
of the past values of EXPR 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.
Figure 6-19 shows an EFREQ device used as a low pass filter.
The input to the frequency response is the voltage across the
input pins. The table describes a low pass filter with a response
of 1 (0 dB) for frequencies below 5 kilohertz and a response of
R_I table type; if left blank, the frequency
table is interpreted in the (input
frequency, magnitude, phase) format; if
defined with any value (such as YES),
the table is interpreted in the (input
frequency, real part, imaginary part)
format.
MAGUNITS units for magnitude where the value can
be DB (decibels) or MAG (raw
magnitude); defaults to DB if left blank.
PHASEUNITS units for phase where the value can be
DEG (degrees) or RAD (radians);
defaults to DEG if left blank.
Fi
g
ure 6-19
EFREQ Part
Example