| Traveling wave tube(TWT) is one kind of Microwave vacuum electronic device, which is widely used in electronic warfare, radar and communication system. Helix traveling wave tube is a kind of TWT, which is the most common in medium and small power field. In order to deal with the challenges of small size, light weight and high reliability of the solid state device, and to meet the requirement of the development of MPM, the TWT needs to be more miniaturized. At the same time, the modern military and communication systems need to cover more frequency, so it is necessary to expand the bandwidth of the TWT. Miniaturization and broadband have become the two main directions of the development of TWT. This paper simulates and designs a miniature broadband Helix TWT which works in 2-6GHz. The main work is as follows:1.Some key technologies of the miniature broadband Helix TWT are described, including dispersion shaping technology for miniaturization and broadband backward wave oscillation suppression technology, attenuation and cutting off technology, pitch jump technology, depressed collector, etc.2.The slow wave structure of 2-6GHz miniature broadband Helix TWT is designed by using the 3D electromagnetic simulation software HFSS. Based on the dispersion shaping technology of miniature broadband Helix TWT, this structure uses the T type rod and the fan-shaped ridge loading. The influence of the distance between the helix and the tube, the size of the metal ridge and the dielectric rod on the high frequency characteristics of the slow wave structure is studied, and these parameters are optimized. The low and weak anomalous dispersion curve which miniature broadband helix slow wave structure requires, the high coupling impedance and low loss characteristics are obtained. In order to suppress the backward wave oscillation, the backward wave oscillation frequency of the slow wave structure is also analyzed, and it is concluded that the coupling impedance of the slow wave structure at the backward wave oscillation frequency is very small,so the backward wave oscillation will not occur.3.The process of beam wave interaction of the 2-6GHz miniature broadband Helix TWT is calculated and optimized by using the two dimensional large signal program ORION. In particular, to suppress the reflection oscillation, a cut is used and a tapered attenuator is arranged at the cut ends. On the basis of this, several slow wave circuit with pitch jump is designed, which includes uniform pitch, negative jump pitch, positive jump pitch, negative- positive jump pitch. Compared with other pitch settings, the effect of negative- positive pitch change is best. At the voltage of 4900 V and the current of 550 mA, the interaction length from 340 mm usually is shortened to 200 mm, in full band, the saturate output power is above 600 W, the saturate gain is above 30 dB, the corresponding electronic efficiency is above 22%, and the two harmonic ratio is less than-6dB.4.By using the two-dimensional large signal program ORION, a three stage depressed collector of the 2-6GHz miniature broadband Helix TWT is simulated and designed to improve the total efficiency of the TWT. In the design process, three methods were adopted to optimize the voltage of electrodes, and the emission coefficient of secondary electron is optimized. In the end, within the 2-6GHz frequency band, the collector efficiency is more than 80%, and the total efficiency is more than 65%, which reaches the requirement for efficiency of the miniature traveling wave tube. |
PDF Full Text Request