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Inductive sheet impedance in transient simulation
Posted 24.10.2014, 13:26 GMT-4 RF & Microwave Engineering, Parameters, Variables, & Functions Version 4.4 1 Reply
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I am using the transient RF module in Comsol 4.4. I want to assign a sheet impedance, Zs, on a boundary such that Etan=Zs*Js, where Etan is the tangential electric field on the boundary and Js is the surface current density on that boundary. This expression is applicable in the frequency domain. To define a capacitive surface impedance in the time domain, I assigned a surface current density of Js=Cs*d(temw.Ex,t), where Cs is the surface capacitance.
However, I am running into trouble when I try to define an inductive impedance. In this case, we need temw.Ex=Ls*dJs/dt which leads to a surface current density of Js=timeint(0,t,temw.Ex)/L. This expression is not acceptable by Comsol.
My question is: How can I define an inductive sheet impedance on a boundary?
Thank you
Hello Nikolaos Chiotellis
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On the boundary you need to be inductive, assign a "Boundary ODEs and DAEs (bode)" with
Dependent variable quantity: Surface current density (let's call this jsurf)
Source term quantity: Electric field
In the Distributed ODE section use:
Source Term: temw.Ex (or the appropriate electric field)
Damping or Mass Coefficient: The value of sheet inductance that is needed.
Mass Coefficient: 0
Initial values:
jsurf: 0
δjsurf/δt:0
Then go in the Electromagnetic Waves, Transient (temw) and add a surface current. The appropriate current density will be the jsurf we defined above.