X-band tandem oscillator-amplifier

Summary form only given. Experiments using a BWO-TWT (backward-wave-oscillator-traveling-wave-tube) tandem driven by a common annular relativistic electron beam were conducted. Two versions of this configuration exist: (1) both the electromagnetic wave and the space-charge wave carried on the beam are coupled from the BWO to the TWT through the connecting aperture and (2) the hole in the coupling aperture is cut off to the electromagnetic wave, so that only the space-charge wave carries microwave signals to the TWT. In the first configuration, it is possible for signals in the TWT region to return to the BWO section, providing feedback. When the two sections operate in different normal modes (for example. TM₀₂ and TM₀₃) that have coincident frequency and wavenumber, the overall gain of the system is maximum at that frequency and oscillation occurs there. In the second version, reflections cannot return to the BWO, which chooses its own frequency, modulating the beam to provide an input signal for the ITWT