Subject: Frequency domain simulation
From: Raghuram Srinivasan (rsriniva@ECECS.UC.EDU)
Date: Mon Jan 28 2002 - 14:49:36 PST
hi group,
Permit us to introduce ourselves as Parthasarathy Narasimhan and Raghuram Srinivasan , students of Dr. Hal
Carter working in the area of Frequency Domain Simulation for VHDL-AMS.
We seek clarification on the following subjects
1. In order to incorporate the Frequency solver to our existing Time domain simulator - SEAMS (which
involves the trapezoidal integration, NR linearization and matrix solver) we propose to do the following,
a. Transalate all Simult. Stmts into a set of freq. stmts with complex variable j, frequency.
b. Apply two-graph MNA to fill up matrix of complex nos. from a.
c. Solve the matrix.
d. write the gain responses and the phase responses of Q( quantities) and f in output files.
e. Increment freq to the next frequency step and goto a , till reached the
final frequency.
In trying to do the above we have the following queries,
a. What is the way to convert Simultaneous statements in time/ frequency to frequencyonly for
solving them by the frequency solver?.
b. Is There a difference in the method for solving a matrix with timeonly components and frequency
only components?.( can we use the same sparse approaches with matrices in frequency, as used in time?)
c. The LRM talks about a domain signal( time /frequency /intialization) where is this Domain
signal set( for time/ frequency calculations)?
d.We know that the Matrix approaches for solving come to a covergence at a time point by iterating,
should such a pattern also be followed in frequency domain solving?
a. The iterations take place because ( of the presence of non-linearities) of the
inclusion of a derivative or an integral operator, but when we convert such a model to
frequency we do not have such non linearity( df(x)/dt = sF(s)) thus is there a need inclusion of a derivative or an integral
operator, but when we convert such a model to frequency we do not have such non linearity( df(x)/dt =
sF(s)) thus is there a need for iteration?
e. Is there any difference between a time and the frequency domain
simulation if the model does not have any spectral components?.
Finally a tangential thought outside LRM,
Could we hope to simulate models in time and frequency depending on the user's choice by appropriately
converting them , and simulating them in time and frequency as the user chooses.
Thanks,
Raghuram &
Parthasarathy
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