how to export the impedance matrix from Feko into Matlab

Hello, I would like to export the impedance matrix from FEKO into matlab but Matlab says that the .mat file is corrupted, any help in this issue?! Thank you in advance

[sumithra Panneer Selvam]

Dear experts, I could export the impedance matrix from feko, impedance matrix contained (NX1) real and NX1 imag parts. I would like to extract Eigen value and Eigen vector from thesereal and imag vectors.eig command needs square matrix of impedance - pl help to extract Eigen value and Eigen vector.

[Ano]

Hello! you have just to reshape them in order to get a square matrix, then you can apply eig .

[sumithra Panneer Selvam]

Thank so much sir... it works...

[sumithra Panneer Selvam]

Dear experts, I need to plot eigen value graph for characteristic modes with eigen value (339X1) and frequency (22X1) in the range of 1.35ghz to 1.5ghz. I have attached .mat file of eigen value(num.mat) and frequency(frequency.mat). Plz help.

[Ano]

Hello! in order to be able to plot that graph the eigenvalues matrix should be of size (339x22) which means that you get the eigenvalues for each frequency sample.

[宇轩]

Excuse me, I am also exporting the impedance matrix from feko, but now I have encountered some problems. The dimension of the impedance matrix I exported from editfeko is 22265x22265, but my antenna array only has 10 units, so it should be 10x10 dimension. Do you know the reason for this? Thank you.

Answer 1

[Klearchos Samaras]

First of all, this *.mat file is not a typical *.mat file. It has a FORTRAN block structure. You can find some useful information here: http://www.feko.info/support/helpcenter/how-to/how-to-read-the-.mat-.lud-.rhs-files-and-.str-files .

I am a FEKO user too. Well, the mat2ascii.exe utility can be used via Command Prompt and the data can be stored in a *.txt file, however the generated file will only contain the rows, columns, real part and imaginary part of the impedance matrix FOR THE FIRST FREQUENCY OF THE SIMULATION. In other words, if you want to simulate at a frequency range (multiple frequencies) the generated *.mat file contains the data of every impedance matrix, however the mat2ascii.exe utility converts only the data of the first impedance matrix of the simulation to *.txt file. Maybe the *.mat file can be easily read in a FORTRAN environment but I don't know that. I have tried to use the f2matlab routine created by Prof. Ben Barrowes, but it failed. I am no expert in programming, though.

*IMPORTANT: There might be a mistake in the *.txt file generated by mat2ascii.exe. It contains some explanatory text in the beginning and then it contains 4 columns with the data of the first frequency impedance matrix. The first column has the numbers of rows, the second has the numbers of columns, the third has the elements of R matrix (real part) and the fourth has the numbers of X matrix (imaginary part). I believe that the third column should be labeled as imaginary and the fourth as real, because the very first element of the R matrix should always be a positive number (it belongs to the main diagonal and R is positive definite), but in my case it is negative.

Answer 2

[Ano]

the process of exporting the impedance matrix from Feko into Matlab will be illustrated. To begin with, the antenna design is build and meshed in CADFEKO without specifying any feeding structure. Then, under the rubric solve/run the EDITFEKO option is activated. EDITFEKO is a script file where the meshed geometry is imported, and the solution configurations are established using the control cards. The foremost cards to be edited are EG card used to set the solution accuracy to double precision, and FR card that serves for setting the simulation frequency (single frequency option is used). After that the PS card is edited, and the option allowing to save the impedance matrix elements to *.mat file is chosen. No further settings are required for FEKO files, and the project is saved. All the remaining manipulations will be managed using Matlab environment. In the other side, in order to generate an impedance matrix for each frequency step, two scripts are used where the same project name is used as in FEKO. The role of each script will be illustrated for a project name ’metalplate’. MultiFrqFeko.m : this script generates the *.pre files for each single frequency step. The content of ’metalplate.pre’ is copied into a temporary file ’metalplate.tmp’, where the line containing ’#this frq =’ , is modified to get the numerical value of the corresponding frequency step. Then, a new file is created having the name of the project followed by the number of the corresponding frequency step (i.e. metalplate1.pre). Finally, the ’dos’ function is called to perform the execution of FEKO files from Matlab.an example of the command execution can be stated as dos(’prefeko metalplate1.pre’) dos(’runfeko metalplate1.pre’) getZFeko.m : this function is used to convert the obtained impedance matrices from mat extension of FEKO into ASCII format using the mat2ascii application, and following command line system(’mat2ascii metalplate1.mat > metalplateASCII1.txt’) application can be Now the resulting impedance matrices can be easily manipulated using Matlab.

[Sumithra Panner selvam]

Dear Ano, Thank you for the answer. I wish to extract the impedance matrices for set of frequencies say (1GHz to 2GHz) from FEKO. Please tell me how to get these impedance matrices.

[Ano]

hello! please use the code attached with the answer it will generate all impedance matrices over the desired frequency band. you should call the function getZfeko.m only. Good luck!

[Woobin Kim]

'ERROR: Could not open the file (FekoFile) .mat' warning appears. How should I solve it?

[Ano]

hello! please make sure to have the application mat2ascii at the same directory as the Matlab scripts. i hope that will be of any help, good luck!

[Woobin Kim]

The part you mentioned is already in the state. What is the problem?

[Ano]

then i would probably check the edit feko file configuration , as i remember at that time i used jacob adam's dissertation (see p.101 you can find it easily). note please make sure to have the feko files with the matlab scripts at the same directory. Good luck!

[Sumithra Panneer Selvam]

Dear Mr.Ano,

I followed the steps given for "exporting the impedance matrix from Feko into Matlab".

i have the following doubts request you to clarify them,

1. I received the below message after running the MultiFrqFeko.m

'runfeko' is not recognized as an internal or external command, operable program or batch file.

'prefeko' is not recognized as an internal or external command, operable program or batch file.

kindly refer the attached screenshot and Suggest me steps to rectify the issue.

2. In the m file getZfeko.m. What should be the structname. Here i have 10 feko files generated like excitation1.pre, excitation2.pre etc.

Sorry for my low matlab skills.

Kindly help me.

[Ano]

Hello!

Please find below my suggestions

1- you need to add feko to the path see this it may help

https://www.mathworks.com/matlabcentral/answers/26289-x-is-not-recognized-as-an-internal-or-external-command-operable-program-or-batch-file

2- the structname = 'excitation' only without any extension.

Hope it helped!

Best regards!

[Sumithra Panneer Selvam]

Dear Mr.Ano,

Thanks for the suggestion. It worked and the feko file are executing. However there is an error (Error using reshape Size arguments must be real integers). as depicted in the figure. It outputs an ascii file that is empty. What can i do about this. kindly help me.

[Ano]

Hello!

Yes, I do remember Having this issue but I believe I solved just by checking all the concerned files. First, check the value of rowsM and start from there it wasn't that hard to solve as far as I remember.

Please post the solution so others and I included could prevent this issue if it happens.

good luck and best regards!

[abdellah touhami]

Dear Mr. Ano,

I want to extract the impedance matrix from feko as you explained, but unfortunately dosen't work, matlab show me an error"matlab could not open the file .mat "

if you please have you an idea.

Best regards

[Ano]

Hello Mr. Abdllah touhami,

If you are trying to open the matrix directly in matlab without using the scripts given in this web page or any other scipts it will not work. Note that both Matlab and Feko have the '.mat' files but it does not have the same meaning. it would be very nice if you could give more details. Good luck and best regards.

Answer 3

[Ano]

Thank you very much for your answer! I just wanted to tell that the real part is ill conditioned that is why you get negative values , you might solve this just by make the negative value = 0. Best regards!