# Symmetry Planes

Geometric symmetry, electric symmetry and magnetic planes of symmetry in a model can be exploited to reduce runtime and memory requirements.

Symmetry in a model applies to the method of moments (MoM) and all hybrid techniques where the MoM is involved, but not in conjunction with the multilevel fast multipole method (MLFMM).

A symmetric model without geometric symmetry defined is not guaranteed to have a symmetric mesh. Such a setup leads to non-symmetric current distributions on the structure.

## Geometric Symmetry

The structure must be symmetric concerning the symmetry plane, while the sources may be arbitrarily located.

## Electric Symmetry

To define an electric symmetry plane, the following must be true:
• The model must be geometric symmetry at the plane.
• The electric current density must be anti-symmetric.
• The magnetic current density must be symmetric.
For example, a physical interpretation of an electric symmetry plane is a plane which can be replaced by a perfect electric conductor (PEC) wall without changing the field distribution. The tangential component of the electric field and the normal component of the magnetic field are zero at such a plane.

## Magnetic Symmetry

To define a magnetic symmetry plane, the following must be true:
• The model must be geometric symmetry at the plane.
• The electric current density must be symmetric.
• The magnetic current density must be anti-symmetric.
For example, a physical interpretation of a magnetic symmetry plane is a plane which can be replaced by a perfect magnetic conductor (PMC) wall without changing the field distribution. The normal component of the electric field and the tangential component of the magnetic field are zero at such a plane.