Research On Helical Slow-Wave Structures Of High Efficiency Space TWTs

As a core of satellite communications, Space Traveling-Wave Tubes (STWTs)must be high efficiency and well linear. The slow-wave structure (SWS) in whichthe energy is exchanged by beam-wave interaction is related to the bandwidthand efficiency of TWT and it determine the performance of the TWT directly.It is the one approach of enhance the efficiency of TWT that improve theefficiency of beam-wave interaction of SWS; moreover, well linear is relatedto the SWS. So the research of SWS is an important aspect about enhance theefficiency of TWT. The paper researched the SWS of high efficiency STWTs andanalyzed that the dispersion and interaction impedance affected by the radicalthickness and pitch of helix. In order to improve the efficiency of STWTs,the method of improve the efficiency of beam-wave interaction of SWS,especially the re-synchronization of beam-wave, are analyzed. Using theprogram of TWTCAD, the efficiency of beam-wave of the X-band STWT is enhancedby the double-taped helical SWS. The coupling equipment of STWTs is designed by thesimulated with software and measured by the vector network analyzer.At last, the measurement of AM/PM is discussed in this paper and the methodbased on the vector network analyzer is given.The mostly work of this paper is as follow:1. The cold characteristics of SWS are simulated by using the program ofHFSS. The finite radial thickness tape helix is replaced by the samethickness vacuum layer laid in an infinite thin tape helix andresearched the effect of the radial thickness on the coldcharacteristics of SWS. The validity of equivalent of radial thicknessis proved and it provides the reasonable gist for theoretic computer. 2. Based on the arts and crafts of helical SWS, it is simulated andresearched that the pitch has had a great affect on dispersion andcoupling impedance in STWTs. The simulated results show that the effectis very small for the project if the variety of pitch of helix lessthan 4%, further more, the experiment shows that the variety of pitchof helix less than 4%.3. In order to improve the efficiency of STWTs, the method of improve theefficiency of beam-wave interaction of SWS are analyzed. Using theprogram of TWTCAD, the double-taped helical SWS of the X-hand STWT isoptimized and designed which enhanced the efficiency and improved thelinear of STWTs. This is the innovations in the paper.4. In order to improve the efficiency and linear, the coupling equipmentof X-band STWT is optimized, designed and measured. The measured resultshow that the average error is less than 2.3% in the bandwidth betweendesigned and measured. The error proves rationality and feasibilityof the method.5. In order to improve the precision of the measurement of AM/PM, themeasurement based on vector network analyzer is given, and that, theerror of measurement is analyzed.