How to set the boundary condition for the peoridical structures?

Hi, mates:

I would like to simulate an antenna array containing 480*320 elements. I heard that the periodic boundary condition can be imposed in order to decrease the dimension of the structure.

The unit cell is a flat square on a holder. The incident wave is a plane wave, illuminating from a centain direction (incident angle: -x-axis, with E-vector pointing to the +z direction). I would like to calculate the diffraction of the array. How can I get the boundary condition correctly? I uploaded the project and the pic of array in order to demonstrate it more visually.

Many thanks for your help.

sorry to mention that the frequency is 40 GHz, not 40 THz as shown in the project file.

I need your help, please.

Hey, To my knowledge, which is limited! In current "EM simulators" like HFSS, FEKO,... you can only define periodic boundary conditions to simulate "infinite" periodic structures. (The solution in some observation points of course would not be much different from a large array like yours, 480*320).

HFSS help directory has a pdf file describing simulation for a "FSS" in that you can find the steps for defining an "infinite" PBC.

There are analytic techniques with use of diffraction theory that they take into account the "effect of truncation" of infinite periodic structures, so we can accurately understand "large but finite" arrays. There are very tough papers about it. It actually is a problem of current research. Search papers by "F. Capolino and L.B. Felsen" also papers by "P.H. Pathak + others", basically papers belong to 2000's. I can send the links to some of them if you want, but they are hard to read.

FEKO can actually compute the farfield for a finite array using the PBC.

How? what is the procedure?

See the FAQ's in the Help Centre on FEKO - EM Simulation Software but you must have a login.

Problem solved!

After defining PBC, when we request farfields, in "advanced tab" we can enter a finite number of elements. That's it.

But still, it does not take into account "edge effects", obviously. What FEKO does is just finding the "element factor" in the infinite structure, and then using a simple array factor, it calculates the pattern of finite array, one can actually export the results of element factor and then write the code for array factor based on antenna books like Balanis or Elliott.

Thanks anyway.

Hey,

I am modelling arrays using FDTD. I have a problem implementing the periodic boundary conditions. Can you please help implement the periodic boundary condition for 2D TM mode. If you can I can post my solution. Thanks in advance