Theory of the microelectronic traveling wave klystron amplifier with field-emission cathode array

A nonlinear theory is developed to predict the gain of a distributed vacuum amplifier employed with field-emitter arrays. Contrary to conventional expectation, it is shown that density modulation of the electrons in the emitting structure is limited by high resistive losses and electronic damping. Therefore, a modified schematic is suggested with the high-frequency modulator separated from the emitter that only dc bias voltage is applied to. Small-signal calculation shows that 15-25 dB gain (with 3 dB bandwidth over 200 GHz) at 100-400 GHz frequency band can be obtained within 1-2 cm drift space length with currently available parameters of field emitters and microstrip transmission lines. Nonlinear calculations predict promising performances of good linearity and 13-20 dBm saturated output power. The suggested distributed vacuum amplifier fully based on microelectromechanical systems technologies would open a new era for the devices operating at the border of millimeter and submillimeter bands. (C) 2007 American Institute of Physics.