Circuit Co-Simulation

How to use openEMS. Discussion on examples, tutorials etc

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Hoejrup
Posts: 3
Joined: Thu 13 Sep 2018, 08:26

Circuit Co-Simulation

Post by Hoejrup » Thu 13 Sep 2018, 11:53

Hello everybody.

I am wondering if it is possible to do a circuit co-simulation in style of e.g. CST?

What I need this for is a birdcage design, where I need to sweep the leg-capacitors and matching to find the the B1-/B1+ ratio (hence the degree of LHCP/RHCP in the MR scanner). I can run openEMS and export a touchstone file, import it to e.g. Qucs and do my matching - however, I really want to calculate my field statistics for various capacitor values. I could add lumped capacitors to the coil and re-simulate the EM model. However, CST does it nicely where it does not need to recalculate the EM model for each iteration, and I wondered if something like this is possible to do in openEMS?

Thanks for the help.
Cheers.

Hale_812
Posts: 171
Joined: Fri 13 May 2016, 02:54

Re: Circuit Co-Simulation

Post by Hale_812 » Fri 14 Sep 2018, 02:12

I think, CST recalculates the capacitor, when changed. HFSS do. It is just possible to avoid iterative remeshing from the scratch. The most time consumed by time-domain solvers goes to iterative remeshing(refining). So, when you reuse pre-meshed models, a false impression of "not recalculating", can occur.

So, what's the problem? in OpenEMS you are a master of yourself. You can tune geometry, or tune dielectric parameters, whatever you want. There's also python interface, but I never tried it. see if there are python scripting availalable in your software, maybe you can automate the things.

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

Re: Circuit Co-Simulation

Post by thorsten » Fri 14 Sep 2018, 19:58

Hi,

all of this is possible. Have a closer look at the Patch_Antenna_Array tutorial.
Furthermore have a look at some of my published papers see: http://openems.de/index.php/Publications
It is just a more implementing it in Matlab approach of course...

regards
Thorsten

Hoejrup
Posts: 3
Joined: Thu 13 Sep 2018, 08:26

Re: Circuit Co-Simulation

Post by Hoejrup » Wed 19 Sep 2018, 19:28

Hi,

Thanks for the replies.

Had a look at the patch array and it I guess it almost does what I want. But let me be more concise.

How do I simulate this: Image ?
(other link: https://ibb.co/iHSFme)

It has two active ports, and some other circuitry - this is the hybrid coupler (and part of a T/R switch) and required for quadrature operation of the birdcage. Now, I can simulate the S-parameters of the hybrid coupler and thus the currents/voltages over frequency at a given input at port 1 in Qucs. Is it possible to input these excitations (over frequency)?

Something like using the AddLumpedPort with AddExcitation (which I can't seem to find the documentation for?)?

Thanks again for the help.
Regards

Hoejrup
Posts: 3
Joined: Thu 13 Sep 2018, 08:26

Re: Circuit Co-Simulation

Post by Hoejrup » Thu 20 Sep 2018, 10:26

So, I might have found what I need:
https://www.ncbi.nlm.nih.gov/pubmed/19570700

Then I just have to implement it in Octave.

Seems pretty straight forward.

Does OpenEMS excite the lumped port with 1 W? Or something else?

Thanks.

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

Re: Circuit Co-Simulation

Post by thorsten » Fri 21 Sep 2018, 19:09

Does OpenEMS excite the lumped port with 1 W? Or something else?
More like something else ;)

You should always normalize everything using the read in port parameters like "ufx" and "ifx" for port x...
I think in some example I do this to show/calculate the radiated powers...

regards
Thorsten

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