periodic boundaries and CMA

Sev Öz

Hi to All,

 

Recently, I saw a paper which uses modal analysis of unit cell ("Characteristic Modal Decomposition of Reflection Phase of a Microstrip Patch Reflectarray Unit Cell, Abdul Maalik, Roberto G. Rojas, Robert J. Burkholder"). 
In the paper, it is written that he FEKO MoM solver is used to compute the first five characteristic
modes of the infinite array.
In Feko, defining a structure with periodic boundaries and CMA are not defined together.
I think that they extracted Zmn of periodic structure and used its characteristic modes in the paper.
I have some questions about this paper if you could answer them I would be appreciated.

- I could not find about the periodicity length of the infinite array in Feko.
Is there a constant value about the block size or is it adjustable or does it depend on the electrical size of the structure?
I need this information to extract Zmn if possible.

- Could we use the characteristic currents calculated in Matlab extracted from Fekos Zmn again in Feko
to calculate calculate near fields, far fields and reflection phase in FEKO with these imported characteristic current?
In the paper, they say that they computed the reflection phase of the structure.
Can I extract the impedance matrix then import the characteristic current into Feko to calculate reflection phase, near fields or far fields, etc.

Best regards

SO

Mel

The periodicity length is equal to the boundary extents, which is set by the user and remains fixed for the entire run.
For example in the example of the Frequency Selective Surface (FSS), example H5 of the Feko Example Guide, the periodicity length there is set to use a variable, d, which is set to a value of 15.2 mm.

The impedance matrix is obtained by requesting to save the *.mat file. This can be requested as shown:

The *.mat file can be converted to ASCII using the mat2ascii utility in the bin folder of your Feko installation. More info is contained in the User Manual appendix A-6 "Read MAT, LUD, RHS and STR files"
(Please note: It is recommended to run Feko with only a single process as the User Manual still requires updating for the formatting/convention for *.mat files produced through parallel running of Feko.)

You can then modify the mat file and read it back into Feko by changing the drop-down box above to read the *.mat file.