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Question regarding degenerate Modes?

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sv1437

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I know that "If different modes have the same resonant frequency then they are called as degenerate modes".

So my question is: " It is useful to have degenerate modes in our design or try to avoid them and how do we identify whether we have degenerate modes".

Any help is appreciated and Thanks in advance.

-sv
 

I think you mean "cut off" frequency instead of "resonant frequency".

Althouh it is not very usual, sometimes it is useful to have degenerate modes in our design. For example, in a rectangular waveguide with square section, the modes \[TE_{01}\] and \[TE_{10}\] are degenerate. Exciting these two modes with a 90º phase shift is a useful way to produce circular polarization.

The most common EM software produce a warning in case you have a port that can support degenerate modes or multiple modes. You can separate multiple ports by modifying the number of modes, and you can separate degenerate modes by expliciting the mode polarization.
 
Thanks danieldani.

For waveguide: degenerate modes have same cutoff frequency.
For cavity resonators: degenerate modes have same resonant frequency.

I think this is the answer:
It depends on the application whether we need degenerate modes or not, and we can figure out whether they exist or not by looking at E-field distribution.

-sv
 
Degenerate modes are very useful in designing dual mode filters where one realize a 2-pole filter with only one (physical) resonators, and a 4-pole filter with two physical resonators. It is also easy to introduce cross couplings between resonators to realize elliptic or quasi elliptic filters.
 
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