From: Stefan Jahn <stefan@gr...>  20110403 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 = 72e3; % [m] height > b = 34e3; % [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. 