What is the difference between these two type of boundary conditions. I am trying to simulate some structures in CST, but I am literally confused between these two as how they are different from each other. Where can the two different boundary conditions can be separated etc.
Any discussion would be highly appreciated.
Regards.
Both of the boundary conditions are used to simulate large periodic structures such as a phase array or high impedance surfaces. The difference is that in case of PBC, a phase shift at the boundary(ies) can be specified. This can be accessed in the "Phase Shift/Scan Angle" tab in the same dialogue box after choosing PBC at one or more axes. The PBC may, therefore, be more helpful when studying near-field problems (as suggested in CST help page) like a single element of a phased array. The phase-shift fields are not editable when the unit cell boundary is chosen. Only scan angles are required for simulation in unit cell boundary condition.
I have used prior Unit Cell boundary conditions to characterize unit cell of a high impedance surface, where a single unit cell is replicated in XY plane. While the principle remains the same in PBC's, I hope someone can clarify more as I haven't used them until now.
With Unit Cell boundary conditions and floquet port , we can get amplittude and phase of transmitted and reflected wave. So Unit Cell boundary conditions are mostly used for designing elements of reflectarray and metasurface.
With periodic boundary condition, we can consider phase shift along axes and it is mostly used for getting dispersion diagram of a unit cell.
As far as I know, for Electromagnetic Band gap structures (EBG) we use periodic conditions in order to simulate infinite periodic array whereas unit cell works with frequency solver.
Thank you all for your responses.
Does anybody know in the unit cell boundary condition, how we can put excitation port (Zmax or Zmin) in the material? (for example put Zmin which is the excitation port in the substrate)?
Mohammad Biabanifard Did you get the reply? I can provide you the method.
Does anybody know, if we want the excitation in the x-axis, and elastic and magnetic boundaries in the y-axis and z-axis respectively? as we simulated the unit cell in the floquent mode? i mean can we change the orientation of the unit cell as we embed that unit cell within the structure instead of the top of the patch? how could I simulate that type of structure in the right way? Any help is appreciated. Thank you.
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