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PSpice: coax cable models

PavelM

Hello,

As far as I've checked, coax cable models in PSpice (TLine.lib library file, which could be open in any ASCII editor) have some definition which looks strange for me. At least, I don't understand where it came from. For example, for RG58C/U coax cable, for its both .model and .subckt options the model series resistance is defined as "r={63.9098u*sqrt(2*s)}". This resistance is intended to model the skin effect losses, which is proportional to sqrt(s).

Later on in the model we can find the commented line with following "r={63.9098u*sqrt(PI2*frq)}". Here it is proportional to sqrt(2*pi*freq), which is a sqrt(s).

Exactly the same file exists in the pre-ORCAD version - MSim.

My question is why it is proportional to sqrt(2*s) in the active model and not to sqrt(s)? Where this factor 2 came from - mathematically / physically?

Sincerely

Pavel

Parents

  • I can not think of "physical" explanation for "2". R should be function of "SQRT(S)". To me physical interpretation still remain same even if I say "SQRT(2s)". R remains proportional to SQRT(s), however proportionality constant changes in both cases. Hope this clarifies.

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  • I can not think of "physical" explanation for "2". R should be function of "SQRT(S)". To me physical interpretation still remain same even if I say "SQRT(2s)". R remains proportional to SQRT(s), however proportionality constant changes in both cases. Hope this clarifies.

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