## [Qucs-help] Rectangular waveguide impedance calculation

 [Qucs-help] Rectangular waveguide impedance calculation From: Julien Hillairet - 2011-03-25 16:10:40 ```Dear Qucs staff, First of all, thank you for providing the world this very nice tool ! It is of great interest, especially for education but also for research (not everyone can afford ADS or Ansoft Designer...) My question is related to the rectangular waveguide line transmission calculator. If the attached picture, I've calculated the properties of a WR284 waveguide (72mm x 34mm) @ 3.7GHz. Qucs gives a characteristic impedance of Z0=430.4 Ohm. However, taking the analytical equations, I obtain (this is matlab code) % TE characteristic impedance of a rectangular waveguide a = 72e-3; % [m] height b = 34e-3; % [m] width c = 299792458; % [m/s] light velocity m = 1; n = 0; % for mode TEmn = TE10 f = 3.7e9; % [Hz] lambda = c / f; k = 2 * pi / lambda; nabla = 119.9169832 * pi; beta = sqrt( k^2 - (m*pi/a)^2 - (n*pi/b)^2 ); Z_TEmn = k * nabla / beta --> Z_TEmn = 455.7152 Ohm Could you explain we what is calculated in Qucs ? (and how ?) Best regards, Julien Hillairet ```

 [Qucs-help] Rectangular waveguide impedance calculation From: Julien Hillairet - 2011-03-25 16:10:40 ```Dear Qucs staff, First of all, thank you for providing the world this very nice tool ! It is of great interest, especially for education but also for research (not everyone can afford ADS or Ansoft Designer...) My question is related to the rectangular waveguide line transmission calculator. If the attached picture, I've calculated the properties of a WR284 waveguide (72mm x 34mm) @ 3.7GHz. Qucs gives a characteristic impedance of Z0=430.4 Ohm. However, taking the analytical equations, I obtain (this is matlab code) % TE characteristic impedance of a rectangular waveguide a = 72e-3; % [m] height b = 34e-3; % [m] width c = 299792458; % [m/s] light velocity m = 1; n = 0; % for mode TEmn = TE10 f = 3.7e9; % [Hz] lambda = c / f; k = 2 * pi / lambda; nabla = 119.9169832 * pi; beta = sqrt( k^2 - (m*pi/a)^2 - (n*pi/b)^2 ); Z_TEmn = k * nabla / beta --> Z_TEmn = 455.7152 Ohm Could you explain we what is calculated in Qucs ? (and how ?) Best regards, Julien Hillairet ```
 Re: [Qucs-help] Rectangular waveguide impedance calculation From: roucaries bastien - 2011-03-28 07:55:29 ```On Fri, Mar 25, 2011 at 5:10 PM, Julien Hillairet wrote: > Dear Qucs staff, > > First of all, thank you for providing the world this very nice tool ! It is > of great interest, especially for education but also for research (not > everyone can afford ADS or Ansoft Designer...) > > My question is related to the rectangular waveguide line transmission > calculator. If the attached picture, I've calculated the properties of a > WR284 waveguide (72mm x 34mm) @ 3.7GHz. Qucs gives a characteristic > impedance of Z0=430.4 Ohm. > > However, taking the analytical equations, I obtain (this is matlab code) > > % TE characteristic impedance of a rectangular waveguide > a = 72e-3; % [m] height > b = 34e-3; % [m] width > c = 299792458;       % [m/s] light velocity > m = 1; > n = 0;         % for mode TEmn = TE10 > f = 3.7e9;      % [Hz] > > lambda = c / f; >     k = 2 * pi / lambda; >  nabla = 119.9169832 * pi; >  beta = sqrt( k^2 - (m*pi/a)^2 - (n*pi/b)^2 ); > Z_TEmn = k * nabla / beta > > > --> Z_TEmn = 455.7152 Ohm > > Could you explain we what is calculated in Qucs  ? (and how ?) Could you try the simulation of TE10 waveguide ? Or it is only linecalc ? Bastien > Best regards, > > Julien Hillairet > > ------------------------------------------------------------------------------ > Enable your software for Intel(R) Active Management Technology to meet the > growing manageability and security demands of your customers. Businesses > are taking advantage of Intel(R) vPro (TM) technology - will your software > be a part of the solution? Download the Intel(R) Manageability Checker > today! http://p.sf.net/sfu/intel-dev2devmar > _______________________________________________ > Qucs-help mailing list > Qucs-help@... > https://lists.sourceforge.net/lists/listinfo/qucs-help > > ```
 Re: [Qucs-help] Rectangular waveguide impedance calculation From: Julien Hillairet - 2011-03-28 08:07:12 ```2011/3/28 roucaries bastien > On Fri, Mar 25, 2011 at 5:10 PM, Julien Hillairet > wrote: > > Dear Qucs staff, > > > > First of all, thank you for providing the world this very nice tool ! It > is > > of great interest, especially for education but also for research (not > > everyone can afford ADS or Ansoft Designer...) > > > > My question is related to the rectangular waveguide line transmission > > calculator. If the attached picture, I've calculated the properties of a > > WR284 waveguide (72mm x 34mm) @ 3.7GHz. Qucs gives a characteristic > > impedance of Z0=430.4 Ohm. > > > > However, taking the analytical equations, I obtain (this is matlab code) > > > > % TE characteristic impedance of a rectangular waveguide > > a = 72e-3; % [m] height > > b = 34e-3; % [m] width > > c = 299792458; % [m/s] light velocity > > m = 1; > > n = 0; % for mode TEmn = TE10 > > f = 3.7e9; % [Hz] > > > > lambda = c / f; > > k = 2 * pi / lambda; > > nabla = 119.9169832 * pi; > > beta = sqrt( k^2 - (m*pi/a)^2 - (n*pi/b)^2 ); > > Z_TEmn = k * nabla / beta > > > > > > --> Z_TEmn = 455.7152 Ohm > > > > Could you explain we what is calculated in Qucs ? (and how ?) > > Could you try the simulation of TE10 waveguide ? Or it is only linecalc ? > > Bastien > > Hello, Well, I'm not sure to understand the question (is linecalc the transmission line calculator?). What I've done is launching the rectangular waveguide transmission line calculator, put in the waveguide dimensions and frequency, then launching the "analyse". The simulator gave me the impedance value (see attached picture on first mail) of 430.4 Ohm in my case. However, using standard equations (e.g. from Pozar's book), I find an other result. I'm not saying the Qucs results is wrong, but I would like to understand what is calculated (characteristic impedance of rect waveguide is really a matter of convention...) Best regards, Julien ```
 Re: [Qucs-help] Rectangular waveguide impedance calculation From: roucaries bastien - 2011-03-28 09:13:18 ```On Mon, Mar 28, 2011 at 10:07 AM, Julien Hillairet wrote: > 2011/3/28 roucaries bastien >> >> On Fri, Mar 25, 2011 at 5:10 PM, Julien Hillairet >> wrote: >> > Dear Qucs staff, >> > >> > First of all, thank you for providing the world this very nice tool ! It >> > is >> > of great interest, especially for education but also for research (not >> > everyone can afford ADS or Ansoft Designer...) >> > >> > My question is related to the rectangular waveguide line transmission >> > calculator. If the attached picture, I've calculated the properties of a >> > WR284 waveguide (72mm x 34mm) @ 3.7GHz. Qucs gives a characteristic >> > impedance of Z0=430.4 Ohm. >> > >> > However, taking the analytical equations, I obtain (this is matlab code) >> > >> > % TE characteristic impedance of a rectangular waveguide >> > a = 72e-3; % [m] height >> > b = 34e-3; % [m] width >> > c = 299792458;       % [m/s] light velocity >> > m = 1; >> > n = 0;         % for mode TEmn = TE10 >> > f = 3.7e9;      % [Hz] >> > >> > lambda = c / f; >> >     k = 2 * pi / lambda; >> >  nabla = 119.9169832 * pi; >> >  beta = sqrt( k^2 - (m*pi/a)^2 - (n*pi/b)^2 ); >> > Z_TEmn = k * nabla / beta >> > >> > >> > --> Z_TEmn = 455.7152 Ohm >> > >> > Could you explain we what is calculated in Qucs  ? (and how ?) >> >> Could you try the simulation of TE10 waveguide ? Or it is only linecalc ? >> >> Bastien >> > > Hello, > > Well, I'm not sure to understand the question (is linecalc the transmission > line calculator?). > > What I've done is launching the rectangular waveguide transmission line > calculator, put in the waveguide dimensions and frequency, then launching > the "analyse". The simulator gave me the impedance value (see attached > picture on first mail) of 430.4 Ohm in my case. > > However, using standard equations (e.g. from Pozar's book), I find an other > result. I'm not saying the Qucs results is wrong, but I would like to > understand what is calculated (characteristic impedance of rect waveguide is > really a matter of convention...) They are two rectangular waveguide implementation: - one in linecalc (transmission line calculator) - one used internally for simulation of rectangular waveguide. Bastien > > Best regards, > > Julien > > ```
 Re: [Qucs-help] Rectangular waveguide impedance calculation From: Stefan Jahn - 2011-03-28 10:12:31 ```Am Fr, 25.03.2011, 18:10 schrieb Julien Hillairet: > Dear Qucs staff, Hello! > First of all, thank you for providing the world this very nice tool ! It > is > of great interest, especially for education but also for research (not > everyone can afford ADS or Ansoft Designer...) > > My question is related to the rectangular waveguide line transmission > calculator. If the attached picture, I've calculated the properties of a > WR284 waveguide (72mm x 34mm) @ 3.7GHz. Qucs gives a characteristic > impedance of Z0=430.4 Ohm. > > However, taking the analytical equations, I obtain (this is matlab code) > > % TE characteristic impedance of a rectangular waveguide > a = 72e-3; % [m] height > b = 34e-3; % [m] width > c = 299792458; % [m/s] light velocity > m = 1; > n = 0; % for mode TEmn = TE10 > f = 3.7e9; % [Hz] > > lambda = c / f; > k = 2 * pi / lambda; > nabla = 119.9169832 * pi; > beta = sqrt( k^2 - (m*pi/a)^2 - (n*pi/b)^2 ); > Z_TEmn = k * nabla / beta > > > --> Z_TEmn = 455.7152 Ohm > > Could you explain we what is calculated in Qucs ? (and how ?) Thanks for reporting the discrepances. Indeed in the TransCalc program it shows Z0=430.4 Ohm, but in the Qucs schamtic simulation you will get the expected 455.72 Ohm... I am going to check, what is wrong in the Transcalc calculation... Best regards, Stefan. ```
 Re: [Qucs-help] Rectangular waveguide impedance calculation From: Julien Hillairet - 2011-03-28 11:28:12 ```> > > Thanks for reporting the discrepances. Indeed in the TransCalc program > it shows Z0=430.4 Ohm, but in the Qucs schamtic simulation you will get > the expected 455.72 Ohm... > > I am going to check, what is wrong in the Transcalc calculation... > > Best regards, Stefan. > > OK. For my own culture, how to you check the characteristic impedance calculated in the schematic simulation ? Best regards, Julien ```
 Re: [Qucs-help] Rectangular waveguide impedance calculation From: Stefan Jahn - 2011-04-03 13:22:15 ```Am Mo, 28.03.2011, 13:28 schrieb Julien Hillairet: Hi! >> Thanks for reporting the discrepances. Indeed in the TransCalc program >> it shows Z0=430.4 Ohm, but in the Qucs schamtic simulation you will get >> the expected 455.72 Ohm... >> >> I am going to check, what is wrong in the Transcalc calculation... >> > OK. > > For my own culture, how to you check the characteristic impedance > calculated > in the schematic simulation ? You can copy a schematic from the transcalc to the qucs schematic. This simulation setup calculates the Zl from S-parameters... Best regards, Stefan. ```
 Re: [Qucs-help] Rectangular waveguide impedance calculation From: Stefan Jahn - 2011-04-03 15:45:16 ```Am Fr, 25.03.2011, 18:10 schrieb Julien Hillairet: > Dear Qucs staff, Hi Julien! > First of all, thank you for providing the world this very nice tool ! It > is > of great interest, especially for education but also for research (not > everyone can afford ADS or Ansoft Designer...) > > My question is related to the rectangular waveguide line transmission > calculator. If the attached picture, I've calculated the properties of a > WR284 waveguide (72mm x 34mm) @ 3.7GHz. Qucs gives a characteristic > impedance of Z0=430.4 Ohm. > > However, taking the analytical equations, I obtain (this is matlab code) > > % TE characteristic impedance of a rectangular waveguide > a = 72e-3; % [m] height > b = 34e-3; % [m] width > c = 299792458; % [m/s] light velocity > m = 1; > n = 0; % for mode TEmn = TE10 > f = 3.7e9; % [Hz] > > lambda = c / f; > k = 2 * pi / lambda; > nabla = 119.9169832 * pi; > beta = sqrt( k^2 - (m*pi/a)^2 - (n*pi/b)^2 ); > Z_TEmn = k * nabla / beta > > > --> Z_TEmn = 455.7152 Ohm > > Could you explain we what is calculated in Qucs ? (and how ?) I fixed that bug in SVN... Thus, in next release there won't be that bug anymore. Anyway, someone need to check the implementation. At least the loss calculations, etc. Best regards, Stefan. ```