## Questions on Simple_Patch_Antenna.m

How to use openEMS. Discussion on examples, tutorials etc

Moderator: thorsten

matt
Posts: 3
Joined: Tue 01 Aug 2017, 19:38

### Questions on Simple_Patch_Antenna.m

I am using the Simple_Patch_Antenna example to learn OpenEMS, and I have some questions about its content.

- First, in the following line:
substrate.kappa = 1e-3 * 2*pi*2.45e9 * EPS0*substrate.epsR;
Is kappa the loss of the material? Is the 1e-3 part the loss tangent? I am not sure why it is multiplied by 2.45e9, especially when the simulation is supposed to cover +/- 1 GHz of the center frequency. If I were to adapt this program to another band, I assume I need to change the 2.45e9 part, right?

- Second, in the following line:
CSX = AddDump(CSX,'Hf', 'DumpType', 11, 'Frequency',[2.4e9]);
What is that frequency supposed to represent? It isn't the design frequency or the resonant frequency.

- If I want to see antenna gain vs frequency, do I need to run nf2ff in the following line multiple times?:

nf2ff = CalcNF2FF(nf2ff, Sim_Path, f_res, thetaRange*pi/180, phiRange*pi/180,'Verbose',1,'Outfile','3D_Pattern.h5');

When I tried that, it appears that you can't do it, something happens to the nf2ff struct that makes it non-reentrant. Can I pass a range of frequencies instead of just f_res?

Thanks,
Matt

thorsten
Posts: 1393
Joined: Mon 27 Jun 2011, 12:26

### Re: Questions on Simple_Patch_Antenna.m

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``s kappa the loss of the material? Is the 1e-3 part the loss tangent?``
Kappa is the conductivity of the material and yes the 1e-3 is the loss tangent indeed.

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`` I am not sure why it is multiplied by 2.45e9, especially when the simulation is supposed to cover +/- 1 GHz of the center frequency. If I were to adapt this program to another band, I assume I need to change the 2.45e9 part, right?``
The loss tangent is a frequency dependent value/loss. Just using kappa it can only be calculated properly at a single target frequency (which here is 2.45 GHz). At every other frequency it deviates more and more but that is not a big issue as the antenna is narrow band.

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``What is that frequency supposed to represent? It isn't the design frequency or the resonant frequency.``
It is supposed to be the resonant frequency (or at least close enough) to record the fields at.

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``When I tried that, it appears that you can't do it, something happens to the nf2ff struct that makes it non-reentrant. Can I pass a range of frequencies instead of just f_res?``
Yes, pass it a list of frequencies. The nf2ff uses by default only one output file name. Which gets reused, thus you cannot rerun nf2ff. There are additional arguments to make it possible, but I don't think you need them.

regards
Thorsten

matt
Posts: 3
Joined: Tue 01 Aug 2017, 19:38

### Re: Questions on Simple_Patch_Antenna.m

Thanks for your quick response. I had another question -- How important is the frequency of the gaussian excitation? The example uses an excitation centered at 2 GHz even though the antenna is for 2.45 GHz. I tried moving it to 2.5 GHz and it changed the input impedance a noticeable amount and resonant frequency by 8 MHz, but didn't have much other effect.

Thanks,
Matt