b. Now let's see how these transmission line characteristics help us
construct a hollow metal tube that will guide RF energy.
6.
Making a guide for RF energy from two-wire line and quarter-wave stubs.
a. Part A of Figure 107 shows a quarter-wave section (stub) connected
to a two-wire transmission line. The voltage and current standing waves of
the quarter-wave stub are as shown. Now let's add a few more quarter-wave
stubs to the line as in Part B of Figure 107.
Figure 107. Hollow Trough Built From Quarter-Wave
Stubs and Two-Wire Transmission Line.
b. The voltage and current standing waves are the same for each stub.
If we keep adding quarter-wave stubs to the two-wire line, the electrical
characteristics of the line do not change, even though the line changes
physically. Finally, you can see in Part C of Figure 107 that if we keep
adding stubs to the line, we get a hollow trough with solid walls. We can
make this trough as long as we want by merely adding more quarter-wave
stubs.
7.
Connecting stubs to the other side of the line.
a. Now let's connect some quarter-wave stubs to the other side of the
two-wire transmission line. We do this as shown in Part A of Figure 108.
You can also see the voltage and current standing waves for the new section.
If we continue connecting stubs to this side of the line, we finally get the
result shown in Part B of Figure 108.
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