Energy Propagation in Waveguides

1-14 Figure 1-16B.—Magnetic fields on a two-wire line with half-wave frames. If the two-wire line and the half-wave frames are developed into a waveguide that is closed at both ends (as shown in figure 1-16B), the distribution of H lines will be as shown in figure 1-17. If the waveguide is extended to 1 1/2!, these H lines form complete loops at half-wave intervals with each group reversed in direction. Again, no H lines can form outside the waveguide as long as it is completely enclosed. Figure 1-17.—Magnetic field pattern in a waveguide. Figure 1-18 shows a cross-sectional view of the magnetic field pattern illustrated in figure 1-17. Note in view (A) that the field is strongest at the edges of the waveguide where the current is highest. The minimum field strength occurs at the zero-current points. View (B) shows the field pattern as it appears !/4 from the end view of the waveguide. As with the previously discussed E fields, the H fields shown in figures 1-17 and 1-18 represent a condition that exists at only one instant in time. During the peak of the next half cycle of the input current, all field directions are reversed and the field will continue to change with changes in the input.