Steps per wavelength in mesh density

[shpongle]

Hi

Could anyone explain to me the concept and significance of mesh density as a function of steps per wavelength? I am asking this in context of a frequency domain EM-solver.

Thanks

 

[boneh3ad]

It's related to the Nyquist rate for time-varying signals, only in this case it is spatial. If you were to take the Fourier transform of your solution, you would only be able to resolve wavelengths of twice your step size or greater. If you are trying to actually build an accurate time or spatial history of the solution including those wavelengths, you would need to have an even more dense mesh.

 

[shpongle]

It's related to the Nyquist rate for time-varying signals, only in this case it is spatial. If you were to take the Fourier transform of your solution, you would only be able to resolve wavelengths of twice your step size or greater. If you are trying to actually build an accurate time or spatial history of the solution including those wavelengths, you would need to have an even more dense mesh.

Thank you for the reply. Could you clarify a bit more ?

I am simulating a Photonic crystal in a frequency range 185-225 THz. The software which I am using is CST Microwave Studio. I am using tetrahedral meshing for frequency domain solution.

I have to alter mesh density due to computer hardware constraints.

The software provides provides two parameters to do this, namely - "steps per wavelength" and "minimum number of steps". May I ask what does "step" refer to and if there is any way to determine the appropriate number of steps per wavelength and minimum number of steps.

 

[boneh3ad]

Step size usually just means the distance between two points in a given direction. I am not familiar with the software, but it sounds to me like you are setting the spacing and number of data points you are solving. Steps per wavelength is how dense the points are and the minimum number is going to determine how many wavelengths you can capture.