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Question defining frequency as a parameter in RF module
Posted 17 mar 2012, 14:15 GMT-4 RF & Microwave Engineering 4 Replies
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Hi all,
I’m working on modeling the electric field of a gold nanowire under an incident electric field and I’m trying to set it up so I can change the frequency without having to manually change the dielectric constant in the materials section. I know the equation I have to use, but I’m having a bit of trouble actually getting it to work with the model.
The equation in question is ε=1-ωp2/ω(ω+iγ), with γ and ωp being constants that I have numbers for. What I’ve done is defined those two as parameters (currently under global definitions) and then further defined ω as another parameter with value 0. I then set a range for it in the “Step 1: Frequency Domain” node under Study 1 and also in “Parametric 1”. I put the equation as the value for the dielectric constant under its materials node.
The problem is that when I try to run it, I get either empty parameter errors or “undefined value found” errors with notes about large degrees of freedom giving NaN/Inf in the vector. I suspect that I’m only supposed to have ω defined one place, but I’m not sure how to do it and still have it work in the dielectric function I put in.
Basically, I’m having some trouble with defining parameters and how to use them in the model itself. Any help is appreciated.
I’m working on modeling the electric field of a gold nanowire under an incident electric field and I’m trying to set it up so I can change the frequency without having to manually change the dielectric constant in the materials section. I know the equation I have to use, but I’m having a bit of trouble actually getting it to work with the model.
The equation in question is ε=1-ωp2/ω(ω+iγ), with γ and ωp being constants that I have numbers for. What I’ve done is defined those two as parameters (currently under global definitions) and then further defined ω as another parameter with value 0. I then set a range for it in the “Step 1: Frequency Domain” node under Study 1 and also in “Parametric 1”. I put the equation as the value for the dielectric constant under its materials node.
The problem is that when I try to run it, I get either empty parameter errors or “undefined value found” errors with notes about large degrees of freedom giving NaN/Inf in the vector. I suspect that I’m only supposed to have ω defined one place, but I’m not sure how to do it and still have it work in the dielectric function I put in.
Basically, I’m having some trouble with defining parameters and how to use them in the model itself. Any help is appreciated.
4 Replies Last Post 22 mar 2012, 03:39 GMT-4
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Posted:
1 decade ago
I'm not sure if I am reading you correctly. But your variable quantity omega = 2.0*pi*freq, right? Comsol's RF module, when in frequency domain mode, is already set up to do parametric sweeps in terms of frequency (freq). So why not just replace your omega variable with 2.0*pi*freq everywhere? It seems to me that that would solve all your issues in specifying omega as a parameter -- or am I missing something?
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Posted:
1 decade ago
Mostly I'm just not sure where to define the freq parameter. It shows up under "Step 1: Frequency Domain", again in the Stationary Solver under Parametric 1, and I'm not sure whether I need to define it as a parameter separately under Global Definitions.
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Posted:
1 decade ago
Define it only under "Step 1:.."
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Posted:
1 decade ago
Hi,
This is not a problem. You first define your parameter in Global definition with unit. And add parameter sweep in your type & give the sweep value. The important thing is that this parameter should be covered as a dependent variable of some function in model itself means this parameter should play a role. I have done it and got sensible results. If still it is not clear send me your file I will do thAT FOR YOU.
Cheers
DEepak
This is not a problem. You first define your parameter in Global definition with unit. And add parameter sweep in your type & give the sweep value. The important thing is that this parameter should be covered as a dependent variable of some function in model itself means this parameter should play a role. I have done it and got sensible results. If still it is not clear send me your file I will do thAT FOR YOU.
Cheers
DEepak