Theoretical and Cold-Test Investigation of a Four-Port High-Frequency System for a 0.14-THz Dual-Sheet-Beam Backward-Wave Oscillator

A four-port high-frequency system for a 0.14-THz dual-sheet-beam hole-grating backward-wave oscillator (BWO) is presented in this paper. The hole-grating slow-wave structure consists of two back-to-back gratings and a diaphragm with a two-hole array, which ensures the electric fields in two electron beam tunnels symmetrical. S-parameter results indicate the four-port system has good transmission characteristics, which could demonstrate the coupling effect of the hole array and the symmetrical properties of the electric fields at two output/input ports. Particle-in-cell simulations show that this high-frequency system could produce stable output signals as long as the current density of one electron beam is higher than the minimum starting current density. It indicates that the four-port high-frequency system can help to reduce the requirement of the dual-beam electron gun and increase the feasibility of the dual-beam hole-grating BWO. The proof-of-principle experiment shows an excellent transmission performance of the system, which agrees well with the theoretical results. All analyses reveal that the four-port hole-grating system could be a feasible high-frequency system of a subterahertz backward-wave radiation source.