.18-40ghz Continuous Wave Traveling-wave Tube Slow-wave Circuit Simulation

Traveling wave tubes with bandwidth, high gain, big dynamic range and low noise characteristics,have become one of important microwave electronic devices in the radar, electronic counter, relay communications satellite navigation, TV broadcasting satellites, remote telemetry and other electronic equipment, remote control. Now, traveling wave tube have been accounted for more than 50% of all the microwave tubes sales.In Traveling Wave Tubes, Slow wave structure's basic role is to provide an axial velocity close to the electron velocity and has a sufficiently strong axial electric field of high frequency electromagnetic wave (TM wave), the electromagnetic interaction with the electron beam, so that signals are amplified. The main characteristics of slow-wave circuit parameters with the wavelength dispersion characteristics and coupling impedance.This paper analyzed the structure of slow-wave circuit, and developed with the German CST company's MAFIA simulation software, on the wavelength dispersion flatness, coupling impedance holding two rods of different shape, clamping methods and loading patterns, clamping lever materials to optimize the contrast spiral size. Optimization results show that: 1) Equivalent loading rod shaped clamping effect is weak, but the shape of the coupling impedance clamping rod is much larger than the other, especially in the most obvious high-40GHz;2) Irrespective of the kind of load form of dispersion flatness greatly increased 15.37% from the maximum dispersion change down to the minimum 0.92%,and coupling impedance has dropped, with the best loading results fell 13.7%;3) 2 clampings has significantly higher clamping the coupling impedance than that of three, four clamping, while the dispersion is less;4) clamping rod material dispersion with the coupling impedance of BN were significantly higher than other kinds of materials,Analyze the difference between a small dielectric constant materials is better;5)The biggest effect on the dispersion and coupling impedance is the diameter changing of spiral;6) the maximum points of the second harmonic frequency is in the low-end; the biggest output loss is in the high-end. Finally, the best results were input the "traveling wave tube CAD" Large signal analysis module for thermal test simulation, and the output simulation results was corrected. In the end, a circuit structure with frequency range of 18-40GH, power of more than 100W, gain of more than 40dB, electronic efficiency of more than 8%, the second harmonic of the slow-wave ratio of less than-3dB was achieved. The results met the need of the research objectives of slow wave structure.