Abstract: An apparatus using field emission techniques to limit voltage on RF transmission lines. A voltage limiter comprises a cathode and an anode housed in an airtight tube, whereby the cathode comprises a field emitter array having a plurality of field tips distributed about the surface of an insulating layer, and a microstrip transmission line overlying the insulating layer and having a predetermined width to form electrical contact with a selected group of the field tips. The microstrip transmission line enables propagation of electromagnetic microwave energy over a bandwidth of multiple octaves. The field emitters enable the generation of a flow of electrons at a predetermined breakdown threshold voltage, without the necessity for an external source to induce electron flow. Generation of the electron flow by the field tips creates a reflection wave on the transmission line that interferes with the incident electromagnetic energy to limit the voltage on the transmission line.