AB Card

This card is used to create a FEM modal excitation, which is the fundamental mode of the associated, infinitely long guided wave structure of the modal port.

On the Source/Load tab, in the Sources on geometry group, click the Modal source (AB) icon.

Figure 1. The AB - Modal port excitation dialog.

Parameters:

New source

A new excitation is defined which replaces all previously defined excitations.

Add to sources

A new excitation is defined which is added to the previously defined excitations.

Name of the modal port

Label of the modal port.

Excite fundamental mode

Select this option to automatically excite the fundamental mode of the waveguide. When this option is selected, the mode type and its indices (

m

and

n

) cannot be specified since they are determined automatically.

Specify modes manually


TE-mode: If this option is checked, a $T E_{m, n}$ mode (also referred to as $H_{m, n}$ ) is used as excitation. This option is only available when Excite fundamental mode has not been selected.
TM-mode: If this option is checked, a ${TM}_{m, n}$ mode (also referred to as $E_{m, n}$ ) is used as excitation. This option is only available when Excite fundamental mode has not been selected.
TEM-mode: If this option is checked (only available for the coaxial waveguide since TEM modes don’t exist in rectangular/circular waveguides), a TEM mode is used as excitation. This option is only available when Excite fundamental mode has not been selected.

Mode index m

The index

m

of the

T E_{m, n}

{TM}_{m, n}

mode which is impressed at the port. Note that for a rectangular waveguide the index m is related to the

u_{1}

direction (for example from point S1 to S2). For a circular/coaxial waveguide,

m

denotes the angular dependency. This option is only available when Excite fundamental mode has not been selected.

Mode index n

The index

n

of the

T E_{m, n}

{TM}_{m, n}

mode which is impressed at the port. Note that for a rectangular waveguide the index

n

is related to the

u_{2}

direction (for example, from point S1 to S3). For a circular/coaxial waveguide,

n

denotes the radial dependency. This option is only available when Excite fundamental mode has not been selected.

Magnitude of impressed mode

The magnitude of the impressed mode (absolute value of the complex amplitude of the impressed mode). The transmitted power of the impressed mode equals half the input amplitude squared.

Note: If left empty or set to 0 then the modal port will act as a passive (sink) port for fields incident on the port.

Phase (degrees)

Phase of the impressed mode in degrees.

Rotation angle $φ_{0}$ (degrees)

Rotation angle in degrees, applicable to circular and coaxial waveguide port shapes only. Specifies the rotation angle in degrees by which the impressed mode is rotated anti-clockwise with respect to the transverse reference axis.