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# Technique for Direct ASTAP Conversion OF Circuit Output Variables From Time-domain TO Frequency-domain

IP.com Disclosure Number: IPCOM000099441D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 6 page(s) / 174K

IBM

## Related People

Thompson, GA: AUTHOR

## Abstract

Models of electronic circuits can be analyzed using ASTAP transient or AC modes to provide, respectively, the time or frequency response of circuit node voltages or element currents. An ASTAP transient analysis output would print or plot the magnitude of a voltage or current with respect to time. Likewise, the output of an AC analysis would provide the voltage or current magnitude/phase with respect to frequency.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 43% of the total text.

Technique for Direct ASTAP Conversion OF Circuit Output Variables From Time-domain TO Frequency-domain

Models of electronic circuits can be analyzed using ASTAP
transient or AC modes to provide, respectively, the time or frequency
response of circuit node voltages or element currents.  An ASTAP
transient analysis output would print or plot the magnitude of a
voltage or current with respect to time.  Likewise, the output of an
AC analysis would provide the voltage or current magnitude/phase with
respect to frequency.

A feature of the ASTAP program called the Fourier source
element allows an AC analysis to be performed at the harmonic
frequencies of a time-dependent input waveform. This waveform is a
table of voltage or current points equally spaced in time, as
described in the ASTAP USER GUIDE, page 85.  A complex waveform may
require a large number of points to describe one complete cycle, and
would, therefore, be tedious to enter manually.  In addition, the
user may require that this complex waveform be generated by ASTAP
through simulation of a potentially complex model.  Built-in ASTAP
functions provide a way of saving those waveforms for later Fourier
spectral analysis.  ASTAP spectral analysis is useful for modeling
many types of electronic circuits where performance would be measured
in the frequency domain. Predicting the amount of distortion in
linear amplifiers and oscillators, or determining the harmonic
content of waveforms generated by switching circuits are typical
examples.

The ASTAP built-in functions PUNCH and PUNCHT allow the user to
save the transient output as a function of time in a separately
allocated dataset.  This dataset is then merged into a new ASTAP AC
analysis program containing the Fourier source element, providing the
points necessary to describe one complete cycle of the time-dependent
waveform.  The output of the Fourier analysis is a plot of the
amplitudes of harmonic frequencies which make up the waveform.  The
spectral content of ASTAP-generated waveforms can then be plotted.
PROCEDURE:

1.  Define the desired ASTAP dataset for the circuit model to
be simulated.  As shown in the following Model Description, include
the PUNCH or PUNCHT statement under the ELEMENTS heading.  This
function, as described on page 168 of the ASTAP USER GUIDE, provides
the method to save a selected output in the form of a table.  The
PTAB or PTAB1 element must also be included as one of the outputs
under the EXECUTION CONTROLS heading. MODEL DESCRIPTION

TRANSIENT ANALYSIS OF A FULL WAVE BRIDGE RECTIFIER CIRCUIT
WHICH COMPRISES THE LINE SIDE OF A SWITCHING POWER SUPPLY.

THIS ANALYSIS INTENDED TO GENERATE NOISE VOLTAGES VS. TIME DUE
TO SWITCHING OF THE DIODES, TO BE LATER CONVERTED TO FREQUENCY-DOMAIN
BY FOURIER ANALYSIS.  SIMULATION INCLUDES LISN. MODEL FWB ();
ELEMENTS
ES1  ,1-2  - (294*DSIN(.377*TIME))
JD1,3A-5=(DIODEQ(1E-5,32,...