I am a recent Qucs user. First at all I want to express my happiness because of this project.
I wrote because I find a mistake in rectline.cpp file on wave impedance, the error origin is on the wave number for vacuum k0, that parameter should be calculated in this way:
k0 = (2.0 * M_PI * frequency/ C0; %% without relative permittivity and permeability.
But the wave number with dielectric should be calculated to calculate beta parameter, so:
k = sqrt (er * mur)) * k0;
beta = sqrt (sqr (k) - sqr (kc));
On the other hand, there are similar problems on rectwaveguide.cpp file (used by qucs-transcalc). the line:
Z0 = k * ZF0 / beta;
Z0 = k0 * ZF0 / beta;
then k0 should be calculated in that file too.
also, the attenuation due to conductor losses should be checked, taking in to account that both files calculate it with different procedures. I think that the correct way is used in rectline.cpp. Because the energy transfer between modes only occurs by irregularities in the waveguide and generally is neglected. Then, if Qucs only calculates TE10 propagation mode there is no reason to take in to account the losses in the other modes.
That is all, thanks for attention.
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