386 Microwave Engineering
In view of Equations 11.8d and 11.10b, the gain BW product is
A g C
m m
BW /=
(11.11)
This product is not a function of frequency. Thus, for high gain, BW has to
be narrow. This restriction is applicable to resonant circuits only. In mega-
watt devices, reentrant cavities and slow wave structures help in getting a
higher gain over a wider BW.
There are several ways to overcome the limitations of conventional tubes.
Inter-electrode capacitance can be reduced by increasing the spacing between
electrodes or by reducing the size of electrodes of the tube. The increase in
spacing of electrodes increases the problems associated with transit time.
The reduction of tube size lowers the power-handling capability. Thus, none
of ...