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Microweave frequency function with temperature

Posted 28 apr 2013, 10:46 GMT-4 RF & Microwave Engineering, Heat Transfer & Phase Change, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions 4 Replies

Duarte Albuquerque
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Hi I am studying an microwave problem in frequency domain, where the frequency of the waveguide problem needs to change during the simulation.

I successufly, made one simulation by definying a frequency in function of the physical time "t".

I need to make the same frequency function but depending of the sample temperature, can be from one temperature probe or the average temperature in the sample.

Has anyone experience in this?

Thanks in advance.
4 Replies Last Post 2 mag 2013, 13:46 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 29 apr 2013, 02:17 GMT-4
Hi

first of all is it a transient time analysis, or a steady state ? If the latter I would recommen to use a frequency domain study, it solves far quicker.

Then what exactly are you needing in the temperature domain ?

Is it a fixed temperature you want to impose or a temperature ananlysis w.r.t. absorption and stress / strain work ?

If you want to impose a temperature, then add a sub node to your linear material with a temperature dependce, define the rest equilibrieum temperature Tref, and make a parametric sweep over the fixed temperature T that you impos

--
Good luck
Ivar
Hi first of all is it a transient time analysis, or a steady state ? If the latter I would recommen to use a frequency domain study, it solves far quicker. Then what exactly are you needing in the temperature domain ? Is it a fixed temperature you want to impose or a temperature ananlysis w.r.t. absorption and stress / strain work ? If you want to impose a temperature, then add a sub node to your linear material with a temperature dependce, define the rest equilibrieum temperature Tref, and make a parametric sweep over the fixed temperature T that you impos -- Good luck Ivar
Duarte Albuquerque
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Posted: 1 decade ago 29 apr 2013, 07:49 GMT-4
Hi Ivar, many thanks for the advice. I will answer your question by topics.

- the heating model needs to be trasient.

- I need the temperature evolution in the sample.

- I can make the material properties (dielectrics) vary with the temperature with an interpolation function.

- I can make the frequency vary in time, by making a global interpolation function writing in study-step1-frequency: freq_time_frit(t)

- But what I require is to impose a dependency of temperature in a function freq_temp_frit(??), I do this because the resonance frequency changes with the material temperature. The material has high "k" so the temperature is almost contant. I tried to put the result of one of my probes (domain point probe) - ppb1 in the freq_temp_frit function. And give a big error message saying that couldn't determinate the frequency and related variables. Any suggestion?

- Since I am studying different input powers in waveguide I need to use the function with the temperature.

Kind Regards,

Duarte Albuquerque
Hi Ivar, many thanks for the advice. I will answer your question by topics. - the heating model needs to be trasient. - I need the temperature evolution in the sample. - I can make the material properties (dielectrics) vary with the temperature with an interpolation function. - I can make the frequency vary in time, by making a global interpolation function writing in study-step1-frequency: freq_time_frit(t) - But what I require is to impose a dependency of temperature in a function freq_temp_frit(??), I do this because the resonance frequency changes with the material temperature. The material has high "k" so the temperature is almost contant. I tried to put the result of one of my probes (domain point probe) - ppb1 in the freq_temp_frit function. And give a big error message saying that couldn't determinate the frequency and related variables. Any suggestion? - Since I am studying different input powers in waveguide I need to use the function with the temperature. Kind Regards, Duarte Albuquerque
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 29 apr 2013, 08:05 GMT-4
Hi

you have (in v4.3a) also the frequency transient and frequency stationary solvers, for given cases (particularly in RF)

--
Good luck
Ivar
Hi you have (in v4.3a) also the frequency transient and frequency stationary solvers, for given cases (particularly in RF) -- Good luck Ivar
Duarte Albuquerque
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Posted: 1 decade ago 2 mag 2013, 13:46 GMT-4
Hi Ivan.

I defined two function one freq_vs_time() and freq_vs_temperature().

If I put in the frequency-transiente study, in the field frequency: freq_vs_time(t) - I obtained the results with the frequency variation in time quite well.

How can do the same with the freq_vs_temperature? How it is the argument tempeture use here? I can use the value of a probe or the average temperature in the sample. I don't know how to put the temperature as an argument here. Any clue?

Thanks in advance,

Duarte Albuquerque
Hi Ivan. I defined two function one freq_vs_time() and freq_vs_temperature(). If I put in the frequency-transiente study, in the field frequency: freq_vs_time(t) - I obtained the results with the frequency variation in time quite well. How can do the same with the freq_vs_temperature? How it is the argument tempeture use here? I can use the value of a probe or the average temperature in the sample. I don't know how to put the temperature as an argument here. Any clue? Thanks in advance, Duarte Albuquerque

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