Distributed Impedance
The Distributed Impedance node adds a distributed impedance boundary condition to a model.
The Harmonic Perturbation subnode (it is of the exclusive type) is available from the context menu (right-click the parent node) or on the Physics toolbar, click the Attributes menu and select Harmonic Perturbation. For more information see Harmonic Perturbation — Exclusive and Contributing Nodes in the COMSOL Multiphysics Reference Manual.
Use this boundary condition to model a thin sheet of a resistive material connected to a reference potential Vref.
The layer impedance can be specified either with the bulk material conductivity σs, the relative permittivity εr and layer thickness ds, or directly with the surface resistance ρs and capacitance Cs. Assuming DC currents, the equation is:
For the Frequency Domain and Time Dependent study types, this boundary condition is slightly more sophisticated and accounts also for capacitive coupling. The equations are:
Distributed Impedance
Enter the reference potential Vref (SI unit: V). The default is 0 V.
Select a potentially complex-valued Layer specification — Thin layer (the default) or Surface impedance.
•
For Thin layer, enter values or expressions for the:
-
Surface thickness ds (SI unit: m). The default is 5·10−3 m (5 mm).
-
Electrical conductivity σ (SI unit: S/m) and Relative permittivity εr (dimensionless). The defaults take values From material. For User defined, enter different values or expressions. The default electrical conductivity is 1·10−2 S/m and the default relative permittivity is 1.
•
For Surface impedance, enter values or expressions for the Surface resistance ρs (SI unit: Ω ·m2) and the Surface capacitance Cs (SI unit:  F/m2). The default surface impedance is 1·10−8 Ω ·m2 and the default surface capacitance is 0 F/m2.