1-23
Q-23. What term is used to identify the forward progress velocity of wavefronts in a waveguide?
Waveguide Modes of Operation
The waveguide analyzed in the previous paragraphs yields an electric field configuration known as
the half-sine electric distribution. This configuration, called a MODE OF OPERATION, is shown in
figure 1-29. Recall that the strength of the field is indicated by the spacing of the lines; that is, the closer
the lines, the stronger the field. The regions of maximum voltage in this field move continuously down
the waveguide in a sine-wave pattern. To meet boundary conditions, the field must always be zero at the
"b" walls.
The half-sine field is only one of many field configurations, or modes, that can exist in a rectangular
waveguide. A full-sine field can also exist in a rectangular waveguide because, as shown in figure 1-30,
the field is zero at the "b" walls.
Similarly, a 1 1/2 sine-wave field can exist in a rectangular waveguide because this field also meets
the boundary conditions. As shown in figure 1-31, the field is perpendicular to any conducting surface it
touches and is zero along the "b" walls.
Figure 1-29.—Half-sine E field distribution.
Figure 1-30.—Full-sine E field distribution.
