Study On The V-band Folded Waveguide TWT And Novel Structures

V band is an important atmospheric attenuation window.V-band traveling-wave tube(TWT)prevails nowadays around the world as amplifier device for the near field security communication,satellite communication and electronic countermeasures.With respect to Europe,America,Japan and other countries,domestic development and utilization of the V band is lagging behind.At present,a 20 W V-band TWT with helix slow-wave structure is in prototype stage,but when the frequency rises to this band,the helix becomes very small,which restricts the power capacity,precision machining,heat dissipation,reliability and environmental adaptability.Therefore,study on the other types of slow-wave structures becomes urgent to improve our level in the V band TWT application.As the core part where the electron beam and EM wave interact for energy transmission,Slow-wave structure(SWS)determines the performance of a TWT.The research started from some all-metal and simple slow-wave structures,mainly introduced open rectangular waveguide grating and folded waveguide(FW),then chose the FW TWT and the novel structures to be research objects according to the practicability,feasibility,development and technology accumulation.The FW TWT has advantages for the high power capacity,simple structure,low-cost and precise fabrication,robust performance,fine heat dissipation and so on.It is also propitious to work from centimetre wave band to THz band by scaled design,which can be applied in space communication,electronic countermeasures,radar,and remote sensing as the broadband,high power and miniature amplifier.Based on the theoretical research,a sample tube was designed and made.Then,we finished the experiment study,including small signal test such as standing-wave ratio and large signal test such as power and bandwidth.In order to promote the total efficiency up to 10%,we designed and fabricated a three-stage depressed collector for the TWT.To obtain higher performance,we have designed three practical novel FW structures and carried out the little signal and large signal studies,which provide supports for the development of improved FW TWT.Compared to the normal structure,the novel structures promote the output power notably and restain the bandwidth.The main work and innovations of this dissertation are as follows:1.Based on the theoretical research,we designed and fabricated a V-band FW TWT and then finished the cold and hot test.Above 30 W output power and 5 GHz bandwidth of V band was obtained,which is a leading level in china.2.In order to promote the total efficiency up to more than 10%,we designed and fabricated a three-stage depressed collector for the TWT,which overcome the insulation proplem for the over 10 kV multiple miniature collectors.Based on the software simulation and manufacturing experience,the total efficiency achieved 12.9% by calculation.3.In order to improve the output power,we designed a right-angle rectangular groove loaded FW.With RF characteristics and large signal beam-wave interaction research,we found that the new structure not only increases the power by 30% through the 5 GHz bandwidth but also reduces the circuit length by 20%.It is capable of 5 GHz bandwidth and 50 W power,which is suitable for higher power and broadband V-band TWT.4.In order to reduce the operating voltage,increase the reliability and simplify the structure for processing,we designed an outer-rectangular groove loaded FW SWS of 10.5 k V operating voltage.With small and large signal study,we found that the new structure improves the power,gain,and provides 5 GHz bandwidth together with 30 W power,which is suitable for the low-voltage and broadband V-band TWT.5.In order to improve the output power more notably,we designed an inner-rectangular groove loaded FW.With small and large signal study,we found that the new structure can improve the performance at higer frequency in the working band because the interaction impedance doesn’t continuely decrease as frequency going up.It is capable of 70 W output power in V band with 4 GHz bandwidth or 50 W with 5 GHz bandwidth using only 66% of the normal circuit length,which is suitable for miniatured higher power and broadband V-band TWT.