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Re: Antenna simulation result different from experiment with NanoVNA

Diane BONKOUNGOU
 

Hi Brian,
Thanks for your reply, attached is my code. I put the dielectric at 4.8
it's FR4. I started with 4.29, my PCB was made by PCBway company. I remark
that when I increase permittivity the frequency decrease.
I also try to put a thickness to my copper traces, I finally forgot this
Idea.
After I changed the metal trace with the copper having losses. *%CSX =
AddMetal( CSX, 'ifa' );* change this with the second line

*CSX = AddConductingSheet( CSX, 'ifa', 59e6,
70e-6); %* 59 copper conductivity, 70e-6 is the losses
Also, I try to put a layer of copper in the PCB because it is a 4-layer PCB
and it gives me 2.66GHz, otherwise, I have 2.8GHz.
My PCB is 0.8mm thicker, with 4 layers of elements. And yes, you are right,
the mesh size can be a big factor. I spend a lot of time on the mesh part.
I tried using Detect edge but I get errors all the time. I ended up doing
the meshing by hand.
-I also check the simulation box position my PCB is inside, but I am
wondering if the position is good.
Best regards

Le jeu. 1 sept. 2022 ¨¤ 13:59, Brian Howie GM4DIJ <brian@...> a
¨¦crit :

On 01/09/2022 11:31, Diane BONKOUNGOU wrote:
Hello everyone,
I used OpenEMS software for my simulation and I got simulation results
that are very different from my experimental result, I have a PCB antenna
whose resonant frequency is around 2.4GHz. I design the same thing on
OpenEMS but the simulation gives me a resonant frequency of around 2.66GHz.
Such a difference of 0.2GHz is important in RF, isn't it? Knowing that the
frequency range of Bluetooth Low Energy is 2.4-2.5GHz.
I have calibrated very well my NanoVNA and my experiment result must be
good. I know that because I tested the Texas instrument PCB IFA antenna and
I get the same result as in their Datasheet.
Can you recommend a free tool for antenna simulation?
I have searched but I can only find OpenEMS based on the FDTD method.
The others are professional and paid tools for PCB trace antenna simulation.
Best regards.
Can you upload the file and I'll have a look The dielectric constant you
chose might differ from the real one depending on the material. There
are also issues in getting the mesh riggt.


I have a couple of PCB antennas for 1.3, 2.3 and 3.4GHz which are ok on
the nanoVNA , I was planning to model. them . They seem to have a
stripline matching section which might be tricky to model accurately.

Brian


--
Brian





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