Let's start with the load. With the same
25Ω
25
Ω
resistor for the load, and plot its
admittance
Y
L
Y
0
=2
Y
L
Y
0
2
. If we start moving away from the load towards the
generator, in about
0.10λ
0.10
λ
we again run into the circle which represents
ReYs
Y
0
=1
Y
s
Y
0
1
. This is such an important circle is has gained its own
name, and it is frequently called the matching
circle Figure 1.
Note that to find out how far we had to move, we had to
start at relative position
0.25λ
0.25
λ
as our zero, or reference location. Point "B" seems to
be at about
0.35λ
0.35
λ
on the scale, and since we started at
0.25λ
0.25
λ
, the distance is
0.35−0.25=0.10
0.35
0.25
0.10
. At "B",
Y
s
Y
0
=-1.0+0.7j
Y
s
Y
0
-1.00.7
. Thus, if we add a susceptance
jB
B
with a value of
j0.014Ω-1
0.014
Ω
-1
we would again match the line. Positive susceptance
comes from a capacitor as well, and so
Figure 2
shows how we match.
Note that we are not
required to go to
point "B". Any point on the matching circle that we can get to
is fair game. Another such point is "C" in
Figure 1. This is at a distance of about
0.40λ
0.40
λ
from the load. At "C",
Y
s
Y
0
=1.0+0.7j
Y
s
Y
0
1.00.7
and so we would put in an inductor, with a susceptance
1jωL=−(j0.014Ω-1)
1
ω
L
0.014
Ω
-1
Figure 3.
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