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From: Christian Friesicke <christian.friesicke@tu...>  20080716 12:41:51

Hey guys, the devellist is probably not the best forum for a request like this but I have one rather simple question about the Qucs Technical Paper published at http://qucs.sourceforge.net/tech/technical.html In the Mathematical Background you give a formula for renormalizing Sparameters to a new set of port impedances (formula 15.1). Can you give me a reference (e.g., to an IEEE paper) where this formula comes from? I know of one reference, JC Tippet, IEEE Trans. MTT, Vol. 30, No. 5, May 1982 (see Appendix V, formula (7)) which basically contains something very similar to formula 15.1 (using a different nomenclature). Comparing Tippet's formulation with yours, I am wondering where the square root in your [A]matrix is coming from? According to Tippet, we would have [A]=[E][R] (using your nomenclature) but that does not agree with your definition of [A]. I would appreciate any help. Regards, Christian Friesicke PS: About me  I am currently doing my diploma thesis at Hamburg University of Technology (TUHH). My research is about nonuniform transmission lines, and I have tinkered a lot with portions of code from Transcalc (microstrip, coupled microstrip), which I ported to Matlab. I have also done some improvements to the stability of the code (analysis and synthesis). Transcalc seems dead :( but luckily it is kept alive in qucstranscalc. I decided to read the list here because I wanted to feed back some of my improvements and ideas when time permits. 
From: roucaries bastien <roucaries.bastien@gm...>  20080716 13:06:13

On Wed, Jul 16, 2008 at 2:41 PM, Christian Friesicke <christian.friesicke@...> wrote: > Hey guys, > > the devellist is probably not the best forum for a request like this but > I have one rather simple question about the Qucs Technical Paper published > at > http://qucs.sourceforge.net/tech/technical.html > > In the Mathematical Background you give a formula for renormalizing > Sparameters to a new set of port impedances (formula 15.1). Can you give > me a reference (e.g., to an IEEE paper) where this formula comes from? I have planned a full rewriteof this stuff but it is quite difficult due to complex impedance issue. A good fundation paper is "Power Waves and the Scattering Matrix" Kurokawa, K. , IEEE MTT, 1965, see eq 32. > I know of one reference, > JC Tippet, IEEE Trans. MTT, Vol. 30, No. 5, May 1982 (see Appendix V, > formula (7)) > which basically contains something very similar to formula 15.1 (using a > different nomenclature). Comparing Tippet's formulation with yours, I am > wondering where the square root in your [A]matrix is coming from? > According to Tippet, we would have [A]=[E][R] (using your nomenclature) > but that does not agree with your definition of [A]. > > I would appreciate any help. > Regards, > > Christian Friesicke > > > PS: About me  I am currently doing my diploma thesis at Hamburg > University of Technology (TUHH). > My research is about nonuniform transmission lines, and I have tinkered a > lot with portions of code from Transcalc (microstrip, coupled microstrip), > which I ported to Matlab. I have also done some improvements to the > stability of the code (analysis and synthesis). > Transcalc seems dead :( but luckily it is kept alive in qucstranscalc. I > decided to read the list here because I wanted to feed back some of my > improvements and ideas when time permits. One of my collegueat uni have just done a phd thesis about this thematic see http://ethesis.inptoulouse.fr/archive/00000462/01/boussalem.pdf (in french). It is based on the hill equation. Could snd you privatly his email Regards bastien > >  > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblincontest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Qucsdevel mailing list > Qucsdevel@... > https://lists.sourceforge.net/lists/listinfo/qucsdevel > 
From: Claudio Girardi <claudio.girardi@vi...>  20080716 20:45:02

Christian Friesicke wrote: > Hey guys, > > the devellist is probably not the best forum for a request like this but > I have one rather simple question about the Qucs Technical Paper published > at > http://qucs.sourceforge.net/tech/technical.html > > In the Mathematical Background you give a formula for renormalizing > Sparameters to a new set of port impedances (formula 15.1). Can you give > me a reference (e.g., to an IEEE paper) where this formula comes from? > > I know of one reference, > JC Tippet, IEEE Trans. MTT, Vol. 30, No. 5, May 1982 (see Appendix V, > formula (7)) Hello, besides the one mentioned by bastien I might add also another nice paper, R. B. Marks and D. F. Williams, "A General Waveguide Circuit Theory," Journal of Research of the National Institute of Standards and Technology 97, pp. 533562, Sep. Oct. 1992 which also deals with the problem of complex reference impedances. > My research is about nonuniform transmission lines, and I have tinkered a > lot with portions of code from Transcalc (microstrip, coupled microstrip), > which I ported to Matlab. I have also done some improvements to the > stability of the code (analysis and synthesis). > Transcalc seems dead :( but luckily it is kept alive in qucstranscalc. I > decided to read the list here because I wanted to feed back some of my > improvements and ideas when time permits. Yes, the original transcalc has been sleeping for quite some time now, and will likely continue to live a new life as QucsTranscalc. If you have done any improvements to the code I will be anyway interested in them, as the developer of the original coupled microstrip code, code which proved to be quite difficult to implement without bugs... I think there still might be a couple of bugs which were corrected in QucsTranscal but not in transcalc. Regards, Claudio 
From: roucaries bastien <roucaries.bastien@gm...>  20080717 08:59:43

On Wed, Jul 16, 2008 at 10:44 PM, Claudio Girardi <claudio.girardi@...> wrote: > Christian Friesicke wrote: > > Hey guys, > > > > the devellist is probably not the best forum for a request like this > but > > I have one rather simple question about the Qucs Technical Paper > published > > at > > http://qucs.sourceforge.net/tech/technical.html > > > > In the Mathematical Background you give a formula for renormalizing > > Sparameters to a new set of port impedances (formula 15.1). Can you > give > > me a reference (e.g., to an IEEE paper) where this formula comes from? > > > > I know of one reference, > > JC Tippet, IEEE Trans. MTT, Vol. 30, No. 5, May 1982 (see Appendix > V, > > formula (7)) > > Hello, > besides the one mentioned by bastien I might add also another nice > paper, R. B. Marks and D. F. Williams, "A General Waveguide Circuit > Theory," Journal of Research of the National Institute of Standards and > Technology 97, pp. 533562, Sep. Oct. 1992 which also deals with the > problem of complex reference impedances. Yes, a pretty good reference. A pretty good sum up of the two approaches is the excellent anritsu note: Application Note, Arbitrary Impedance. Accurate Measurements In Almost Any Impedance Environment Qucs implement only real impedance S parameter. Complexd one are buggy (even if we try to implement youla wave) Regards Bastien >> My research is about nonuniform transmission lines, and I have tinkered a >> lot with portions of code from Transcalc (microstrip, coupled microstrip), >> which I ported to Matlab. I have also done some improvements to the >> stability of the code (analysis and synthesis). >> Transcalc seems dead :( but luckily it is kept alive in qucstranscalc. I >> decided to read the list here because I wanted to feed back some of my >> improvements and ideas when time permits. > > Yes, the original transcalc has been sleeping for quite some time now, > and will likely continue to live a new life as QucsTranscalc. If you > have done any improvements to the code I will be anyway interested in > them, as the developer of the original coupled microstrip code, code > which proved to be quite difficult to implement without bugs... I think > there still might be a couple of bugs which were corrected in > QucsTranscal but not in transcalc. > > Regards, > Claudio > >  > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblincontest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Qucsdevel mailing list > Qucsdevel@... > https://lists.sourceforge.net/lists/listinfo/qucsdevel > 
From: Christian Friesicke <christian.friesicke@tu...>  20080718 11:30:52

Hi, thanks for all the pointers to various papers/articles. I didn't know that the NIST Journal of Research was publicly available. Even though I had heard of the paper by Marks and Williams, I thought it would be too complicated to get my hands on it (Google Scholar only points to some abstract database, and not to the NIST virtual library). As for the Sparameter renormalization, I stick to real impedances in my code. So it won't be too complicated. regards, Christian Friesicke 
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