Image Number 4 for United States Patent #6909235.
A traveling wave tube (TWT) amplifier includes a beam forming electrode (BFE) and a BFE modulator having a bias-based keyer so that the TWT amplifier signals are keyed off during periods when RF power is not to be amplified. Biasing the beam forming electrode voltage off relative to cathode voltage effectively shuts down the electron beam without shutting down the power supply minimizes power supply stress and significantly improves reliability, so that low-level RF signal input is not amplified, and no significant RF power is output. Likewise, given that no amplification has taken place, no power associated with the TWT amplification function is consumed. Thus, the only power consumed by the TWT amplifier is that associated with the cathode heater and the electronic power conditioner (EPC) used as the electron beam source.