Resistive arc protection for field-emitter-array cold cathodes used in X-band inductive output amplifiers

Field-emitter arrays (FEAs) are desirable for use as cold cathodes for X-band inductive output amplifiers because they can provide higher efficiency and faster turn-on than their thermionic counterparts. Their major drawback is premature failure due to arcing. Display manufacturers have solved this problem by incorporating a resistive layer under the emitters, which limits the current at each tip. However, this high series resistance limits the frequency at which the gate-to-emitter voltage can be modulated, making it undesirable for RF applications. Fortunately, because the resistors under the tips are effectively in parallel, the total emitter series impedance of the array can be reduced by increasing the number of tips in the array. With proper design, the highly resistive layer can provide enough capacitance to act as a bypass at X-band, while still allowing enough resistance at lower frequencies to suppress arc currents. This paper will present design and test results from resistively protected field emitter arrays with a range of resistive layer parameters.