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integrating a lookup table for frequency dependent variables

Posted Nov 27, 2012, 10:13 a.m. EST Version 4.2 7 Replies

Andrea Marie Scholl
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Hi everyone,

I have created a lookup table for frequency dependent values of epsilon_r.
This table includes two interpolation functions: one for the real part (eps_real) and the other for the imaginary part (eps_imag).

In the material browser, I tried to add these two functions as a sum (eps_real + eps_imag) for the expression of the relative permittivity. Unfortunately, this causes an error during computation.

I therefore assume that the way I tried to tackle my problem is not possible.
Does anyone know who to integrate values of an interpolation function of a lookup table into variables for frequency dependent materials?


Thank you.
7 Replies Last Post Mar 27, 2013, 4:09 p.m. EDT
Andrea Marie Scholl
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Posted: 1 decade ago Nov 27, 2012, 10:15 a.m. EST
I meant:
eps_real +j*eps_imag
I meant: eps_real +j*eps_imag
Yevgeniy Davletshin
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Posted: 1 decade ago Nov 27, 2012, 10:26 a.m. EST
What kind of error do you get?

Check documentation for gold nanosphere www.comsol.com/showroom/gallery/12415/
What kind of error do you get? Check documentation for gold nanosphere http://www.comsol.com/showroom/gallery/12415/
Andrea Marie Scholl
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Posted: 1 decade ago Nov 27, 2012, 10:31 a.m. EST
The error that I get is that COMSOL doesn't recognize the expressions for the interpolation functions.
I've checked the spelling twice.

Could my approach actually work or did I already commit a mistake in developing the approach?
The error that I get is that COMSOL doesn't recognize the expressions for the interpolation functions. I've checked the spelling twice. Could my approach actually work or did I already commit a mistake in developing the approach?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 27, 2012, 4:13 p.m. EST
Hi

if you have an interpolation function you should write for a frequency variable "freq"

eps_real(freq)+j*eps_imag(freq)

as the function needs an argument. Only exception if the argument is x,y,z and you have selected the function settings accordingly (file read in interpolation option if I remember right)

--
Good luck
Ivar
Hi if you have an interpolation function you should write for a frequency variable "freq" eps_real(freq)+j*eps_imag(freq) as the function needs an argument. Only exception if the argument is x,y,z and you have selected the function settings accordingly (file read in interpolation option if I remember right) -- Good luck Ivar
Andrea Marie Scholl
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Posted: 1 decade ago Mar 26, 2013, 10:29 p.m. EDT
Thank you for the reference.

Just for the sake of confirmation: It is necessary to type in the value 1 in Units -> function because the electric permittivity has no unit, right?
Thank you for the reference. Just for the sake of confirmation: It is necessary to type in the value 1 in Units -> function because the electric permittivity has no unit, right?
Andrea Marie Scholl
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Posted: 1 decade ago Mar 26, 2013, 10:40 p.m. EDT
Dear Ivar,

when creating the lookup table in COMSOL the two columns are
t for the argument of the function
and f(t) for the function itself.

I am used that t represents time in seconds but I want to create a lookup table for electric permittivity which is frequency dependent.

I have integrated the lookup table with epsilon_real(freq)-j*epsilon_imag(freq).
In the parameters setting I have entered Hz as the unit of the argument and 1 as the unit of the function.

Is this sufficient for the frequency dependecne?
Dear Ivar, when creating the lookup table in COMSOL the two columns are t for the argument of the function and f(t) for the function itself. I am used that t represents time in seconds but I want to create a lookup table for electric permittivity which is frequency dependent. I have integrated the lookup table with epsilon_real(freq)-j*epsilon_imag(freq). In the parameters setting I have entered Hz as the unit of the argument and 1 as the unit of the function. Is this sufficient for the frequency dependecne?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 27, 2013, 4:09 p.m. EDT
Hi

the variable names in COMSOL functions are dummy names, and not linked to the main physics, as interpolation functions was one time set up for time signals, "t" was used, but you can call it with any variable. Look at it as a programming function, any name within the Function is "local" and might have the name of an external "Global" variable so long this is not defined within the scope of the function definition.

I agree this feels sometimes confusing ;)

When loading functions from fields, you have also somewhere the option to use spatial variables (as default arguments) then your function becomes a field and can be called within a local boundary or domain definition, but without the explicit (x,y,z) reference, assuming that the mapping is done correctly

--
Good luck
Ivar
Hi the variable names in COMSOL functions are dummy names, and not linked to the main physics, as interpolation functions was one time set up for time signals, "t" was used, but you can call it with any variable. Look at it as a programming function, any name within the Function is "local" and might have the name of an external "Global" variable so long this is not defined within the scope of the function definition. I agree this feels sometimes confusing ;) When loading functions from fields, you have also somewhere the option to use spatial variables (as default arguments) then your function becomes a field and can be called within a local boundary or domain definition, but without the explicit (x,y,z) reference, assuming that the mapping is done correctly -- Good luck Ivar

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