Far Field Source File in CST MWS

Hello all,

I am trying to do something very simple and cannot seem to get it to work. All i wanna do is make a far field source file for a simple cos^q(theta) pattern. What i need to do is to make the far field source file then use it as an excitation for a I-solver simulation. Please, anyone who understands the formatting of the far field source file respond to this post. The format is not as simple as the following cause i tried that and it did not work:

Re(E_Theta) = cos^q(theta)*sin(phi)
Im(E_Theta) = 0
Re(E_Phi) = cos^q(theta)*cos(phi)
Im(E_Phi) = 0

I got these from the equation for the far field of a cos^q which is:
E(theta, phi) = cos^q(theta) * [sin(phi)* theta_hat + cos(phi) * phi_hat]

This has no imaginary part but when you look at the far field source files generated from CST, they always have an imaginary part, i think that the way that I think that the file expects the theta and phi components is wrong, please anyone who understands the file format or anyone who can help or has alrady made a far field source file ever before. Thanks again guys.

Hi, I never used this feature in CST, so sorry could not directly help you. But I am using another Method of Moments solver (EMCoS TriD), where it is also possible to specify Radiation Pattern Source. Attached is User's Manual - please take a look on chapter 3.5.11 Pattern source block.

You can see also general format description in attached picture.
If you could generate your needed source in this format I could test how TriD solver can handle such a source.

Is your source frequency dependent? In this case format is just little bit different - you need to specify similar block for each frequency.

Hello,

Thanks so much for your reply, i cannot tell you how good it feels to talk to someone about this problem i have been ripping my hair out to get this to work for the last 4 days now! and its just a stupid cos^q(theta) pattern, I couldn't even get a simple dipole to work and dipole is just sin(theta). Well, what would really help me is if you could generate a file with a pattern of cos^q(theta) in spherical coordinates for just a few theta and phi samples, no more than 5 or so for each. Then i can reverse engineer the way that the file is generated and apply the concepts to my file. My file is the same format as yours except my pattern values for E_Theta and E_Phi are in Re( ) and Im( ) part and yours are just Mag( ) and Ph( ). So, if i have a file with the correct pattern in your tool, then i can just convert the values from polar to re/im and then try the file in CST. Please let me know if you could do that for me. Thanks again for your post, i am hurtin over here with this.

I'll try to generate required pattern. What are the q values you are interested in? *Sorry, this is not really my specialisation, I might ask trivial questions*.

I took a look on paper 'Realizable Feed-Element Patterns and Optimum Aperture Efficiency in Multibeam Antenna Systems' by K. S. YNGVESSON, J. F. JOHANSSON,
Y. S. KIM, Y. RAHMAT-SAMII, FELLOW - there they consider values of q as a quadratic function of d/Lambda, i.e. K(d/Lambda)^2 - 0.5.

Thanks so much, we are so fortunate to have people willing to help eachother out like you, thanks again. Okay, so the q values i will need are 0.396, 3.4879, and 8.199 but i only need one of these to start, the easiest will prob be the 8.199. Thanks again, let me know if there is any other information you need.

See attached archive with matlab codes and Radiation Pattern Source files for EMCoS EMC Studio. Is this what you expected?

What you are going to excite by these patterns?

Wow, that is exactly what i expected, thanks so much, i really appreciate this. I should be able to go from this file to the file for my program. Thanks again, I will let you know how it goes but once again, thanks so much, I am going to give you a thank you but is there any other way to give you some points or something?

PS:
It worked, my problem was always assuming the imaginary part is 0, when in actuality it will not becuase of the sign involved with the real part. Thanks again, problem solved!

Also, I really really really appreciate the matlab script to generate the pattern files, thanks again!

Glad to hear this. Keep the topic updated if you have further issues.

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