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Lumped Capacitor in the RF Module, eigenfrequency
Posted 04.08.2015, 03:43 GMT-4 Low-Frequency Electromagnetics, RF & Microwave Engineering, Studies & Solvers Version 4.4 4 Replies
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I'm using 4.4, and I realize it is impossible to add Lumped Capacitor and Lumped Inductor in RF Module Eigenfrequency study.
(but lumped elements with Z value is possible, and Lumped Capacitor or Lumped Inductor is possible for frequency study)
I think it is because Comsol is looking for a frequency, so if you only give capacitance, how it can calculate impedance lol. My current solution is hand calculate a Z value with approximated frequency and input this Z value, then look for eigenfrequency.
Then my question is, how to use lumped element with capacitor type in Comsol? Is 5.1 or 5.0 can fix this problem? Or any other brilliant solutions?
Regards,
Jared
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Capacitance, inductance and pure (real) resistance can all be calculated from the geometry and the material properties of the material involved. However, complex impedance Z(f) is obtained when you close a circuit, at a given frequency f so you need more than just the components, often it's derived by the V/I ratio
But FEM works on densities (of flux current ...) so you need to integrate these fluxes over the boundaries to get "lumped" values for the impedance estimations. This is done already inside the definitions of the Terminals and other lumped ports nodes of COMSOL, that is why they are handy and make you gain quite some time
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Good luck
Ivar
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The question you are asking here has to do with the usage of the Lumped Element boundary condition in combination with the eigenfrequency analysis. The lumped element condition does apply a lumped impedance based upon the equation Z=1/j omega C, where omega has to be known. Now of course, if we solve an eigenvalue problem, omega is what we are solving for. Thus, what we must do is provide a so-called "eigenvalue linearization point" in the eigenvalue solver settings. For complete details on this, please read the section "Lossy Eigenvalue Calculations" in the RF Module users guide, as it describes how to deal with this case.
Best,
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Thank you very much for your help, it works!
Best,
HJ
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