A hollow waveguide is a transmission line that looks like an empty metallic pipe. It supports the propagation of transverse electric (TE) and transverse magnetic (TM) modes, but not transverse electromagnetic (TEM) modes. There is an infinite number of modes that can propagate as long as the operating frequency is above the cutoff frequency of the mode. The notation
The electromagnetic analysis of a rectangular waveguide is well known, and can be easily found in the literature, like [1]. Here we list only final results that can be used to verify the simulation results.


A section of a rectangular waveguide is modeled in CST STUDIO SUITE® and the first 3 modes are calculated and their field distributions analyzed. The dimensions used are the standard for WR90 waveguide. Because the background is set to perfectly electrical conductor (PEC) material, we only need to model the vacuum inside the waveguide, with a waveguide port at each end. The boundary conditions are “electric” in all directions, and the model is simulated using the time domain solver. In this model the first 3 modes are calculated, and E and Hfield monitors are setup at 10, 13.5 and 15 GHz.
Parameter  Value  Description 
a  22.86 mm  Big edge dimension 
b  10.16 mm  Small edge dimension 
l  40 mm  Length of the waveguide 
Model Construction Watch Video
Download Model File (Student Edition) Download Model File
In Fig. 4 we show the dialog window of the Port Mode Information at 10 GHz. This can be found by rightclicking on the port in the dialog tree, and selecting “Object Information”.
In Table 2 we compare the results shown in Fig. 4 and compare with the analytical results given by the Eq. 1 – 3.




Mode  simulated  analytical  simulated  analytical  simulated  analytical 
TE 
6.54  6.56  158.46  158.05     
TE 
13.02  13.12      174.71  177.99 
TE 
14.63  14.76      223.81  227.48 
Note that for the higher modes, there is no real beta at 10 GHz. That is because those modes are below the cutoff frequency, and the propagation constant becomes entirely imaginary (alpha). As Eq. 2 demonstrates, this indicates that
In the 2D/3D Results, we can see the field patterns for each mode. Fig. 5 shows the E, H and Jfield patterns for each mode at 15 GHz. Fig 6 shows the field pattern for the TE
Your session has expired. Redirecting you to the login page...