--- In LTspice@..., Philip Bellingham <rmhc78a@...> wrote:
Tony,
While LTspice may not be the ideal tool for RF design, it can still be quite
useful.
You are correct that it does not have native support for producing a Smith
chart. However, some clever contributor to this group has provided a means to
plot the graticule of a Smth chart and impedance curves with frequency markers
(Files > Examples > Apps > SmithLTspice.zip).
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With respect to LTspice handling s-parameters, it certainly can. The .NET
command computes network parameters in an AC sweep. The HELP files says in part,
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"This statement is used with a small signal(.AC) analysis to compute the input
and output admittance, impedance, Y-parameters, Z-parameters, H-parameters, and
S-parameters of a 2-port network. It can also be used to compute the input
admittance and impedance of a 1-port network. This must be used with a .AC
statement, which determines the frequency sweep of the network analysis."
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There is an entire section in the tutorial section of this groups files devoted
to s-parameters in LTspice (Files> Tut> S-Parameter).
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All the best,
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???? - Philip
Hello Philip,
Thanks for the info.
I'm aware of the Smith chart add-on, which is why I said native. It's clever as you said, but not slick enough for serious design work; even the author concedes it's crude. I'm also aware that adding the .net directive enables an .ac analysis to generate S-parameters; and indeed, I make a lot of use of this feature. But you cannot use S-parameters as input data. This was my point, although I admit I didn't make that very clear.
There are also various utilities that claim to generate SPICE subcircuits from S-parameter files, but this is something of a holy grail, which is why the only commercial product that really claims to have cracked this with multiport demonstrable accuracy over decades of frequency range costs thousands of dollars.
Regards,
Tony
