in modal analysis (eigenmode CST) of unit cell , we obtain modes
what is the relation of these modes with TE and TM ?
I don't know, and there is not enough information in your pictures for me to work it out. If you plotted the three components of the field, or an arrow plot, it would be easier to work out which mode you have. The mode looks like the e-field has a z component, and has one half wave in x and two half-waves in y, so it may be a TM mode, TM21 or TM12? I don't think that will be the third mode in order of wavenumber, but it might be. One of the values in the table is usually the wavenumber, so you can identify the mode from that. I can't see it in your picture. It is simple to generate the wavenumbers in excel given the dimensions and frequency.
Within a structure, the eigenmodes correspond to all possible field distributions. Some of or all of these eigenmodes may get excited as soon as there is a nonzero projection between the incident fields on a field distribution associated with the eigen-fields. Eigenmode analysis will give you all possible field distributions. Now, once you will analyze your complete design in a full-wave analysis (time domain or frequency domain), based on your excitation source (port etc.) definition, and overall structure geometry, you filed distribution could be classified as TE or TM.
Check to see if it has a z component of the electric field. If not it is a TE mode. Check to see if it has a z component of the magnetic field, if not it is a TM mode. Ignore z fields that are much smaller than the maximum fields, those are just calculation errors.
Hello,
It is very easy to understand. After simulating your structure using solver in CST, you will get number of modes, whatever number you would be given. Then TE and TM come when see the plot of modes. There you can easily check the index number of TE and TM by checking its vector plot or contour plot and also you can check by checking the direction of wave propagation in Z direction.
Thanks,
Smrity Dwivedi Malcolm White Nadeem Ashraf
thanks for your answers dears . generally when a structure (like spoof surfce plasmon polaritons (SSPP)) have wavenumber greater than k0 it will confine electromagnetic field and so is a good transmission line
is it true??
my question is about cutoff frequency of dispersion curve
what this freq show?
it means bellow this freq structure is a good transmission line??
what happen at cutoff ( gradient of dispersion =0 so wave velocity is zero) ?
If the wavenumber is greater than the free-space wavenumber then there is no free-space plane wave travelling in any direction that can match the phase of the signal on the line, so different parts of the line cannot contribute coherently to radiation, and radiation is small.
Below cut-off, the wave cannot propagate on the structure. At cut-off the velocity at which energy travels along the structure is zero. In hollow rectangular waveguide this is the frequency at which the energy just bounces from side to side in the guide. It has the same phase over the whole length of the guide (so infinite phase velocity) but the energy does not travel along the guide (the group velocity is zero). Look at the crossed-plane-wave description of waveguide field patterns.
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