HFSS15: Current Sources

A current source in HFSS can be defined on a surface located anywhere in the 3D problem space, but it typically makes sense to place the source on a surface between two conductors such that it injects the user defined total current onto the conductors. A current source is implemented in HFSS by weakly enforcing the jump across the source surface of the tangential component of the magnetic field, , to be related to a surface current density, :

where is the unit normal of the surface. The surface current density can be expressed as where is the magnitude and is the unit vector in the direction of current flow.

The unit vector is in the direction of the user defined current flow direction line. The magnitude is obtained by first assuming that the surface is a rectangle such that the width, w, is equal to the area divided by the length of the current flow direction line. The magnitude is set equal to the total current specified by the user divided by w. Note that any source surface is allowed but considering the definition of the surface current density it is recommended to only use a planar rectangular surface.

A current source cannot be used to extract S-parameters. For S-parameter computations of an HFSS design involving a mixture of ports and current sources, all the current sources are kept opened by treating the current source surface as a natural boundary condition where no special behavior of the electric field is explicitly enforced.