| Wideband and high power is a main tendency of traveling wave tube(TWT)production,no matter the challenge from semiconductor amplifying device or the development of TWT itself.With the expansion of bandwidth and the improvement of output power,not only the performance of TWT will be enhanced,but also brings great economic benefits.The article will show some researches on beam-wave interaction of ultra-wideband TWT based on the demand of output power and secondary resonance wave restrain.The content of the article contain the following aspects:1.Research of the discipline about diversification of slow wave characteristics caused by transformation of high frequency structure.Helix diameter,pitch,wing diameter and wing angle will obviously influence slow wave characteristics.Adjusting the thickness and width of helix,the outside diameter and width of support rod could slightly change dispersion and coupling impedance.2.Proposing and verifying the feasibility and high-efficiency that using the mutation of wing diameter restrain the second harmonic of ultra-wideband TWT.Applying the traditional mutation of pitch,second harmonic of most frequency point can't be restrained but the effect of mutation of wing diameter will be better.3.Researching the influence of normalized phase velocity on output power,at the same time,obtaining the value range of phase velocity at 4GHz and 18 GHz.As we all know,in order to obtain an efficient beam-wave interaction,we should let phase velocity less than the speed of electronic beam,however,there is still no accurate figure.The TWT in different frequency actually need different phase velocity.Referring to the best phase velocity at 4GHz to 18 GHz,the article will show the range of normalized phase under two different anomaly degree of dispersion to improve the output power as much as possible.4.Coming up with an efficient distribution of interaction that can improve output power of the full band.Firstly,ensuring phase velocity of frequency point at edge belong to the range of the third works,besides,in order to make electronic beam and electromagnetic wave are synchronous,dispersion should be more flat and coupling impedance should be bigger on input section.Finally,abnormality of dispersion are supposed to be more intensive on output segment to restrain second harmonic.5.Increasing electronic efficiency with mature speed synchronize again technology.To make the biggest electronic efficiency at 18 GHz,reducing pitch properly in a position in front of saturation point of output power,additionally,ensuring pitch and starting point in a right place.6.Fulfilling calculation on high frequency structure and beam-wave interaction of ultra-wideband at 4GHz to 18 GHz,which is based on the methods above and design process for wideband TWT.In the article,output power at 4GHz to 18 GHz will exceed 150 watt and electronic efficiency will exceed 15%,what is more,rejection ratio of second harmonic will less than-3.5dBc. |
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