Twin traveling-wave tube amplifiers driven by a relativistic backward-wave oscillator

Experiments demonstrate stable frequency and relative-phase angle output from twin traveling-wave tube (TWT) amplifiers driven with the redirected signal from a high-power backward-wave oscillator (BWO). The experimental X-band apparatus employs a single generator to produce three independent electron beams which simultaneously drive the BWO and TWT sources. The BWO spontaneously generates up to 14.1 MW peak, 25 to 15-ns long pulses over a current-tunable bandwidth of 9.6%. The BWO power extracted upstream is split and redirected into twin TWT´s for amplification. The TWT´s produce up to 9.0 MW pulses over an 800 MHz instantaneous bandwidth. Across the amplifier´s full-width half-maximum pulse duration of 10 to 20 ns, a relative-phase angle of better than 15° is maintained between TWT´s for an 11.0 to 11.7 GHz range. Experiments characterize the gain, relative-phase angle, and efficiency of twin-TWT output as a function of RF-drive frequency and beam current. These experiments are the first to demonstrate the feasibility of relativistic TWT´s for phased-array applications, and increase the limited data base documenting relativistic-TWT operation