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Results of Frequency Domain Analysis

Posted 10.07.2014, 17:19 GMT-4 RF & Microwave Engineering, Studies & Solvers Version 4.3b 2 Replies

Jonathan Karsch
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Hi all,

I have been running frequency sweeps (in the RF module) on a magnetic wire simulation recently in COMSOL, and the qualitative results we get from looking at slice plots of the magnetic field and arrow plots of the current are important for verifying the model without going to the hard numbers. Values in the simulation obviously oscillate because they aren't at DC, and the question has come up of what exactly COMSOL is presenting in color plots and other data. Is it the average amplitude at each point, the RMS, possibly just a snapshot of the system at a certain time? I can't find the answer in any documentation, so perhaps it's an obvious answer that I am looking too much into, but a definitive answer would definitely help.

Thank you,
Jonathan
2 Replies Last Post 17.07.2014, 13:50 GMT-4
Robert Koslover Certified Consultant
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Posted: 1 decade ago 12.07.2014, 00:20 GMT-4
Most field quantities (components of E and H, for example) typically plotted in frequency domain solutions are snapshots at a particular fixed phase. You can change the phase used for the plotted solution. Go to Results --> Data Sets --> Solution 1 (if that is your solution) and you'll see a "Solution at angle (phase):" box, which defaults to 0 deg. Change it to 90 or something else and replot your results! Another thing you can do to observe how phase matters is to create an animation. Under Results, right-click on Export, then choose Animation. Under Animation Editing, where it says "Sequence type:" click the pull-down box that defaults to "Stored Solutions" and instead pick "Dynamic data extension." You will also have to specify a file name for the .gif movie under Output. You can use this to generate a movie that steps through phase.

By the way, I consider this to be one of Comsol's least intuitive design features. I mean, think about it: "Dynamic data extension"? How about simply giving the user a choice of plotting the results versus "phase" instead, huh? Personally, I'm guessing that "Dynamic data extension" must be a literal translation into English of whatever word is used to mean "phase" in the original Swedish! <grin!>
Most field quantities (components of E and H, for example) typically plotted in frequency domain solutions are snapshots at a particular fixed phase. You can change the phase used for the plotted solution. Go to Results --> Data Sets --> Solution 1 (if that is your solution) and you'll see a "Solution at angle (phase):" box, which defaults to 0 deg. Change it to 90 or something else and replot your results! Another thing you can do to observe how phase matters is to create an animation. Under Results, right-click on Export, then choose Animation. Under Animation Editing, where it says "Sequence type:" click the pull-down box that defaults to "Stored Solutions" and instead pick "Dynamic data extension." You will also have to specify a file name for the .gif movie under Output. You can use this to generate a movie that steps through phase. By the way, I consider this to be one of Comsol's least intuitive design features. I mean, think about it: "Dynamic data extension"? How about simply giving the user a choice of plotting the results versus "phase" instead, huh? Personally, I'm guessing that "Dynamic data extension" must be a literal translation into English of whatever word is used to mean "phase" in the original Swedish!
Jonathan Karsch
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Posted: 1 decade ago 17.07.2014, 13:50 GMT-4
Thank you! That's very helpful to know.
Thank you! That's very helpful to know.

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