Reseach On V-band Microstrip Slow-wave Structure

Traveling-wave tube(TWT) which is widely used in many fields such as radar and communication relay has wide bandwidth, high output power, low noise, long life and high RF efficiency. The conventional slow-wave structures(SWS) which contain helix structure, folded waveguide and ladder are popular used in TWTs. With the rapid development of modern electronic technologies, the high frequency and miniaturization direction become the two significant directions in the field of vacuum electronics. The fabrication techniques of microstrip meander-line can employ microelectro-mechanical systems(MEMS) which include a kind of microfabrication techniques such as wet chemical etching, deep reactive ion etching, ion beam milling, laser ablation, Galanoformung and Abformung.As a 2-D structure, the fabrication technique of MEMS is more reliability, uncomplicated and repeatability than that of 3-D. Moreover, the microstrip meander-line SWS for TWT has many outstanding features such as wide-bandwidth and low-voltage. Microstrip line slow-wave structure can be a good match with solid state circuitry. So it can be used for microstrip lines TWT final stage millimeter-wave power module power pusher. The research work slow-wave structure of the microstrip line TWT has an important role to direction of the millimeter-wave and terahertz. These microstrip slow-wave structures have the characteristics of low the normalized phase velocity value. The main characteristics of the microstrip slow-wave structure have dispersion, interaction impedance, transmission and beam-wave interaction. The main contents and innovations are as follows:1. The variant N-shaped microstrip slow-wave structure is proposed for V-band TWT. The three dimensional models of attenuator and input and output structure are established by using the CST. The dispersion characteristic, interaction impedance, transmission characteristic and beam-wave interaction are simulated by utilizing the HFSS and CST. The results showed that: the output power of variable N-shaped microstrip lines TWT can be 87 W, corresponding to gain of 29.4d B and average efficiency of 12.2%, respectively.2. In order to improve the interaction impedance, the Ω-shaped microstrip slow-wave structure is proposed. Compared to the variant N-shaped microstrip slow-wave structure, the Ω-shaped microstrip slow-wave structure has higher interaction impedance.3. The simulations of high frequency characteristic, transmission characteristic and beam-wave interaction of Ω-shaped structure are accomplished by using the simulation software HFSS and CST. The results showed that: peak output power of Ω-shaped microstrip line TWT is 115 W, corresponding to gain of 30.6dB and average efficiency of 14.3%, respectively.