Touchstone Issue Resolution Document  (TSIRD)


TSIRD ID#:      1.1    
ISSUE TITLE:    Sparse Matrix Mapping
REQUESTER:      Bob Ross, Teraspeed Consulting Group for Interconnect Task Group
DATE SUBMITTED: February 26, 2010, April 23, 2010
DATE ACCEPTED BY IBIS OPEN FORUM: April 23, 2010

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STATEMENT OF THE ISSUE:

The number of data pair columns for an N-port grows by an N-squared
relationship.  When N is large, the N-port description in Touchstone
syntax requires a large file, and its Touchstone model can require a
large amount of memory.

Many passive interconnect parts have physical symmetries and regular
patterns.  These parts have identical entries in N-port descriptions.
Also, the physically distant paths have small values or terms in the
corresponding Touchstone models that can be omitted for most analysis.

A sparse syntax extension is useful to fully describe the corresponding
N-port model with a smaller Touchstone file for the values of N now
needed.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

TSIRD1 proposes a index-pair mapping solution using two new keywords:

  [Number of Sparse Labels]
  [Sparse Matrix Mapping]

A full set of rules is described in tsird1.1.pdf:

  http://ibis.org/tsirds/tsird1.1.pdf

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

TSIRD1

A minimal set of rules and syntax could be been specified.  The proposed
choices were made to add clarity.  For example, the index-pairs that are
documented as '(i,j)' could have been documented as 'i,j'.  The '<string>'
portion of sparse-labels could have been removed.

The existing keyword [Matrix Format] was originally used for allowing one
data-pair instead of two for reciprical data.  Because its arguments of
Full, Lower, and Upper could be applied for index-pairs, [Matrix Format]
was chosen instead of selecting a new keyword.

With reduced entries under Network Data, a smaller amount of data is needed
to document completely the N-port. The rules for all other keywords remain
as if the full N-port data were entered.

April 23, 2010 - The examples were corrected to [Version] 2.1 and
element was changed to elements in the fourth to last paragraph.

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ANY OTHER BACKGROUND INFORMATION:

Many people in the Interconnect Task Group made key suggestions or
observations.

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