# MoM matrix and eigencurrent

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```Syntax:  mat2ascii FILENAME [b]
Filename:   name of the *.mat file (with extension)
Options:
b         block number (e.g. for multiple frequencies)
(default is first block, b=1)```

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Please can you send me an example of the syntax

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okay i got it. It id (b) not where b is for block number

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I am so grateful for your continuous support. I still have questions as I continue to use FEKO and I hope you don't mind.

Please, I want to know if it is possible to get the information of the external edges. I also want to confirm that the values given for the current density vector on the triangle is for the triangle centre or for the whole triangle?

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Assuming you are referring to edges that form the boundary of a surface, what information about these edges are you looking for?

The surface current (which is a vector quantity represented as a surface density in Ampere/meter (A/m)) can be exported to the *.out or a *.os file where the vector quantity will be reported on the triangle centre and the current magnitude will be reported for triangle corners. The *.str file reports the weighting coefficients of the matrix solution so that can be used to construct the surface current at any point on the model.

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On 04/09/2017 at 9:55 AM, RenierM said:

The currents (or then the solution to the matrix problem) is exported in the STR-file. This will however not be the Eigen currents as this is what you will calculate using the CMA Eigen equation.

This statement is confusing me. What is the difference between the eigen-current and the solution of the matrix problem. Please I would love clarification

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They are both [Nx1] vectors of basis function coefficients that describe a surface current density.
An eigencurrent vector is one of N possible solution vectors to an eigenproblem. The solution to the MoM matrix problem is a single current vector that describes the currents as excited by the sources present in the problem.

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Wilcon thanks so much for you continuous patience with me. I am tying to really understand this subject as I find it interesting. Okay taking the MoM matrix and solving the eigenproblem of XI = lambdaRI should give me lambda and I which is the eigenvector?

The MoM matrix problem is just one current vector non-withstanding the mode? I am still lost in figuring out the difference betwen eigencurrent vector and solution to the MoM matrix problem. Because I am thinking they are both the same just different as per mode of analysis. Please help me clarify and if there is an opportunity to have a private chat or conversation, I also would not mind. Thank you.

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Also to mention that solving the eigenproblem does not give me the same lambda as outputted from feko

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Quote

...solving the eigenproblem of XI = lambdaRI should give me lambda and I which is the eigenvector?

Correct.

Quote

Also to mention that solving the eigenproblem does not give me the same lambda as outputted from feko

Are you sorting your modes. FEKO will report eigenvalues with the smallest magnitude (most significant) up until the number of requested modes.

Quote

...the difference betwen eigencurrent vector and solution to the MoM matrix problem

To use your syntax from above, with Z = R + jX, and V the source (or driving vector), the MoM matrix problem is:

ZI = V

I suggest perhaps doing a study of the different CEM methods before delving too deeply into Characteristic Mode theory.

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Hello,

I'm getting started   to use FEKO. I want to extract matrixes from feko in order to do some calculations in matlab. Here; since generating the feko file I obtain a set of 6 matrixes - f1.mat.0; f1.mat.1........f1.mat.5 . So I want to know why I am obtaining those files and what does they contain....

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Hi,

The number of matrix files written out is equal to the number of processes used for parallel runs (I assume this was a parallel run with 6 processes).

Please look at the documentation for an explanation of the file format.

Search for "Read MAT, LUD, RHS and STR Files".

Regards,

Renier

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On 9/4/2017 at 4:35 AM, Renier Marchand said:

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The std2ascii file is now part of the installation (see the description in the link below):

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On 2/12/2019 at 2:20 AM, Renier Marchand said:

Hi,Reniersince our university buy FEKO last year, the altair company give us an 2017 edition. So could u provide those exe here?  Thanks.

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Hi XuWang,

I have attached the utility below.

Regards,

Renier

str2ascii.exe

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Hi

I started using FEKO 2018 student version. I nedd to know the order of the RWG bases..I mean how they are related to triangles? Can anyone please help? Thank you.

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