Research Of Millimeter Wave Extended Interaction Devices’ Slow Wave Resonant System

The electromagnetic wave with range of 30GHz-300 GHz is millimeter wave, which is among microwave, infrared, light waves. It has some peculiarities: first, narrow beam; second, the very wide bandwidth; third, the size of the millimeter wave device is relatively much smaller than microwave devices; fourth, compared with the laser, its propagation characteristics is influenced smally by the climate, close to all-weather features.Extended interaction devices(EID) is a kind of millimeter wave vacuum electronics developed in the 1960 s with interaction mechanism base on traveling wave tube and klystron, which mainly contains extended interaction klystron oscillator(EIK) and extended interaction(EIO). Compared with traveling wave tube and klystron, extended interaction devices can achieve higher gain, higher efficiency and large enough bandwidth, whose slow wave resonant system combines the advantages of traveling wave tube and klystron.EID working at millimeter wave and submillimeter frequency has great development potential, on account of its characteristics of compact structure, light weight, small size, wide bandwidth, low operating voltage and high power, etc. At present, EID is being increasingly applied to satellite communications, deep space topology imaging, climate observation and so on.In this article, the 0.14 THz EID’s slow wave resonant system is mainly studied. The high- frequency electromagnetic simulation software CST(Computer Simulation Technology) and CHIPIC software are respectively used for the cold simulation and hot simulation. We analyzed the influence of each structural parameter on the slow wave resonance system and get a set of optimal values to build the model. Then, the dispersion curve is calculated on the basis of the former built model. According to dispersion curve and the result of PIC simulation, we did analysis and verification to mode competition, and choosed ? mode as the operating mode, which provided reference to future design. Particle-in-cell(PIC) simulation shows that the beam-wave interaction efficiency is about 22%, and operating mode is ? mode and the microwave output average power is 1.98 kW at center frequency 149.4GHz when voltage is 18.2kV and current is 0.5A. And under the same conditions of structure parameters, electron beam cross-sectional area and density, the final simulation results show that the sheet beam EIO is superior to the pencil beam EIO. This is because the longitudinal electric field on the cross section of sheet beam is more uniform than pencil beam, resulting in that sheet beam is modulated more uniformly and has better social effect; in addition, sheet beam’s coupling impedance is larger than pencil beam.