Re: [SI-LIST] : Linpar 2-D field solver experiences?

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From: Scott McMorrow ([email protected])
Date: Thu Nov 30 2000 - 14:12:30 PST


LINPAR and MULTLIN are available from Artech House
and from Amazon:

 LINPAR $375



Larry Miller wrote:

> ***WHERE*** do you get Linpar, please? The only references I find are to a 1992 book/disk package with a DOS version.
> I would really appreciate a pointer to where I can get it from someone!
> Thanks,
> Larry Miller
> -----Original Message-----
> From: [email protected] [SMTP:[email protected]]
> Sent: Thursday, November 30, 2000 10:47 AM
> To: [email protected]
> Subject: Re: [SI-LIST] : Linpar 2-D field solver experiences?
> In a message dated 11/21/00 9:58:22 PM Pacific Standard Time,
> [email protected] writes:
> Has anybody used the Linpar CAD 2-D field solver?
> I've used ansoft, CALIF, Greenfield, Pacific Numerix,
> and have recently come across Linpar.
> Linpar seems to be a very easy to use CAD tool, and
> seems very cost effective (sub $500) for a general
> purpose 2-D field solving tool for simulating impedance
> and crosstalk.
> Dave:
> I have not tried the latest Windows version of LINPAR, but I have used MSDOS
> versions of both LINPAR and its companion program LINRES for almost a decade
> with very positive results/success. I also have used Agilent's APPCAD,
> Polar's CITS25, and UltraCAD's T-Line Calculator. Relative to the real world
> (i.e., documented by measurement on known physical layups), LINPAR has been
> one of the best.
> A MAJOR ADVANTAGE of LINPAR over the other free (or low cost) programs is
> that it can address multiple traces, including different sizes,
> simultaneously. Because of the coupling of adjacent traces in today's densely
> routed boards, the individual trace loading and crosstalk is important to all
> SI engineers. Most pay an arm and a leg for CAD programs that (rightly)
> address this issue, but their accuracy (as you might have noticed) has often
> been questioned in this SI forum.
> The (purely text) output is in the form of L-R-C-G matrices, as well as Er
> (effective), propagation speed, and individual trace impedances. For
> crosstalk and waveform simulations, these matrices must then be imported into
> the LINRES program, sources and loads defined and saved into additional
> files, and then run. The simulation plots from LINRES are very basic, but I
> have compared the results with HSPICE W-element simulations and FOUND
> NEGLIGIBLE DIFFERENCE (except in the HORRENDOUS difference in price).
> However, LINPAR/LINRES (MSDOS) has definite limitations. The ease of use is
> cumbersome to execute several combinations of trace widths, trace spaces,
> dielectric thicknesses, Er values, etceteras. Because of the original MSDOS
> program size limitations (from a decade ago), more complex structures are
> limited in size. And, with today's thin dielectrics, stripline trace
> thickness and shape has an impact on the impedances and crosstalk that is not
> accounted for (infinitely thin traces are the default for stripline), unless
> you draw a full 2D picture of the configuration. This latter approach is
> cumbersome and time consuming, but can be done. The infinitely thin traces
> yield higher (~5%) Zo predictions than reality unless the dielectric
> thickness is >5 x trace thickness. However, microstrip trace thicknesses ARE
> accounted for.
> NOTE: The newer Windows version of LINPAR may have corrected all of the above
> negatives/limitations. Further comments from any who have tried it are kindly
> solicited.
> Dave, if you have received other responses NOT sent to the SI List, could you
> summarize them and post them?
> Mike
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
> (408)727-5697
> *** Serving Your Needs with Technical Excellence ***

Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231

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