
266 Microwave Engineering
or negative by changing the stub length over a stretch of half wavelength.
Since due to physical limitations the stub length cannot be made zero, it is
often allowed to exceed the half wavelength limit. The plungers used may
be of contacting and non-contacting type. Contacting plunger (Figure 7.51a)
remains in contact with inner and outer conductors whereas in a non-con-
tacting plunger, there are gaps between plungers and the two conductors.
When matching is to be accomplished by means of single stub only, the dis-
tance between the load and the stub needs to be varied. The structure of a
variable-length section or li ...