
436 Microwave Engineering
conductance representing the copper losses, G
B
is the beam loading and G
L
represents the load conductance.
Effective conductance of this circuit is related to the effective shunt resis-
tance R
sh
as
G = G
C
+ G
B
+ G
L
= 1/R
sh
(12.58)
The necessary condition for oscillations in the cavity is
|−G
e
| ≥ G (12.59)
The electronic admittance Y
e
given by Equation 12.57 can be written in the
rectangular form as
Y
e
= G
e
+ jB
e
(12.60)
where G
e
and B
e
are the real and imaginary parts of Y
e
.
The phase of Y
e
is
π
/2 when
θ
0
′ is zero. The rectangular plot of Y
e
is a spiral
as shown in Figure 12.15. Any value of
′
0
for which the spiral ...