RF phase control in a high-power high-efficiency klystron-like relativistic backward wave oscillator

The klystron-like relativistic backward wave oscillator (RBWO) with a dual-cavity extractor has demonstrated 10 GW output power with 48% efficiency in recent simulations. To realize radio-frequency (RF) phase control for the purpose of coherent power combining, a high-power high-efficiency klystron-like RBWO with an input signal is presented. In the device, an independent input cavity is introduced before the resonant reflector to reduce the leakage power from the input port, and the applied RF signal is injected into the input cavity through a mode convertor and a coaxial waveguide along the magnet, which avoids separating the magnet by the injection waveguide, and suppresses the asymmetric modes excited in the input cavity. For a frequency difference of 15 MHz between the input signal and free-running klystron-like RBWO, an input power of 10 MW is sufficient to control the phase of 10 GW output microwave. (C) 2011 American Institute of Physics. [doi:10.1063/1.3601522]