Vacuum Electronic Two-Beam Oscillator–Amplifier

This paper describes a new technique to improve the efficiency of conventional vacuum electronic backward-wave oscillator (BWO) by combining the operations of both oscillator and amplifier in a single slow-wave structure (SWS). The conventional backward-wave oscillator is modified by introducing an additional electron beam which is synchronized with the fundamental forward-wave space harmonic and provides amplification like a traveling-wave tube amplifier. As proof of concept, the technique is illustrated using a circular helix SWS and three different beam configurations. The performance of the proposed oscillator-amplifier is simulated at Ku-band and compared with that of the conventional BWO. Presented results show that the new technique improves the DC-to-RF conversion efficiency of the conventional BWO by a factor ranging from three to six, depending on the beam configuration while keeping the length of the SWS unchanged. At the same time, the technique provides greater than 39% electronic frequency tunability. Simulations indicate a maximum DC-RF conversion efficiency of 16.77% and peak output power of 624.5 W from this device. The proposed technique has good potential for applications due to significant improvement in the efficiency compared to a conventional low-voltage BWO.