Excitation Fields

HFSS assumes that each port is connected to a uniform waveguide that has the same cross-section as the port. A waveguide supports an infinite number of modes with a given field pattern and propagation constant.

Therefore, the excitation field is one of the modes specified for a port where mode m can be expressed by:

(1)

where

• Â is the real part of a complex number or function.
• Em(x,y) is the electric field mode pattern of mode m.
• g _m=a_m + jb_m is the complex propagation constant of mode m, where
• a_m is the attenuation constant of mode m.
• b_m is the propagation constant of mode m that determines, at a given time t, how the phase angle varies with z.
• w =2pf is angular frequency of oscillation,
• j >is the imaginary unit, .

In this context, the x- and y-axes are assumed to lie in the cross-section of the port; the z-axis lies along the direction of propagation.