Questions on Simple_Patch_Antenna.m

How to use openEMS. Discussion on examples, tutorials etc

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

Questions on Simple_Patch_Antenna.m

Post by matt » Tue 07 Apr 2020, 02:50

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

Post by thorsten » Tue 07 Apr 2020, 08:31

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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.

Code: Select all

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

Post by matt » Tue 07 Apr 2020, 22:49

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

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