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Hi,

Which value should I use as incident power in a Huygens Box source?

Thanks,
Nani

Hi,

The idea is to use the simulation source power P_s from the primary simulation. This will automate the normalization of the results from the Huygens source simulation: the value is copied to the second field in the Normalization window (...input power for [ P_s ] source power...).

However, you can also just manually edit the second field in the normalization window when extracting the results from the Huygens source simulation.

Can someone verify this:

I set the incident field power in huygens box simulation to equal the total source power from initial simulation.

Then, when I extract results from the huygens simulation, e.g. SAR, I can set the postprocessor to normalize the results with regards to the initial simulation?
If I take the MRI lead pass tutorial example, I could then in the huygens simulation see, how the SAR is affected when changing total radiated power of the birdcage coil?

If I understand this correctly, the incident power simply tells the post-processor, what was the total power of all sources in the initial simulation, and then uses this value for total power in the normalization, e.g.

SARnorm= Pnorm / Ptotal_sim

If anyone from the Semcad crew is reading this, this could be better documented in the manual and in the software itself (e.g. when you extract results from the huygens simulation, the normalization dialog shows the units in W/m^2, which is misleading if you only have edge sources in the inital simulation...).

I have a similar problem with the power scaling of thermal simulations. When scaling the EM source I'm still not quite sure if I scale the power of the whole simulation or only the power inside the field sensor...

Hi there,

I also find this a bit confusing. The way I see it, is that you are breaking a single simulation into 2 steps. In the second step, SEMCAD does not automatically know what power was used in the first step to generate the fields that are used to drive the Huygens source.

I set the incident field power in huygens box simulation to equal the total source power from initial simulation. Then, when I extract results from the huygens simulation, e.g. SAR, I can set the postprocessor to normalize the results with regards to the initial simulation?

Yes, actually that is all the Incident Power setting does. It copies the reference power from the primary/initial simulation to the normalization box, i.e. it automates the power relationship between primary and secondary simulations.

If I take the MRI lead pass tutorial example, I could then in the huygens simulation see, how the SAR is affected when changing total radiated power of the birdcage coil?


Yes.


If I understand this correctly, the incident power simply tells the post-processor, what was the total power of all sources in the initial simulation, and then uses this value for total power in the normalization, e.g.

SARnorm= Pnorm / Ptotal_sim


Yes, that is also how I understand it.

I just did some testing with a setup similar to the MRI leadpass tutorial. I did 5 huygens simulations, with different incident powers each time ranging vom 10W to 1000W.

Now if i check the unscaled results, they are all the same. Erms, Brms, SAR it's all the same regardless which incident power was specified. Is there a bug (i did it with batch processing) or why would it give such results?

I wasn't sure about the incident power i needed, so i wanted to check a couple of setups to find the right one. Now i don't know how to proceed...

Hi,

Now if i check the unscaled results...

does this mean that you did not normalize the results when you extracted them. If so then the fields should be the same, i.e. the incident power is only used during normalization of the simulation results and is not used in the simulation at all.

Yes, that's what i meant.

After some more testing and comparing results of different normalizations i finally understood how it works. Thank you very much anyway