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Clarify loss units for CPW in docs #702

Open edumur opened 7 years ago

edumur commented 7 years ago

EDIT: loss formulas for CPW at see http://qucs.sourceforge.net/tech/node86.html use different units - this is confusing

In the cpwline.cpp it looks like the conductive losses are calculated as if the result of the formula from Ghione is in Neper/meter. However in the Gupta, author claims that the formula is in Db/meter image

Who is right?

in3otd commented 7 years ago

Who is right?

both. (actually the formula you reported above has an error, but not related to the unit of loss)

edumur commented 7 years ago

That's interesting. Do you mean that:

  1. The formula used in the code is correct to give a result in Neper/meter.
  2. The formula in Gupta is incorrectly copied from the source [36]: image

Thanks for very fast reply ;) .

in3otd commented 7 years ago
  1. yes
  2. yes

but checking the sources/references I saw that the Qucs documentation is confusing, since it uses different units for the same quantity in the same chapter, see http://qucs.sourceforge.net/tech/node86.html

edumur commented 7 years ago

Well this is where I started my journey about the formula. If the reference [39], Gupta in the documentation, is wrong, don't you think that should be made clear in the documentation?

in3otd commented 7 years ago

reference [39] is K. C. Gupta, R. Garg, I. J. Bahl, and P. Bhartia, Microstrip Lines and Slotlines, 2nd ed.Artech House, Inc., 1996. which, curiously enough, has the correct expression. I guess the one you quoted above is from the third edition, or?

edumur commented 7 years ago

Good catch! My bad, it effectively comes from the third edition.

I would then say that everything seems correct to me. If you agree, I think this thread can be closed.

And thanks again!

in3otd commented 7 years ago

thanks - I reopened the issue, changing the title to remind to clarify the loss units in the CPW docs