Line The High Frequency Characteristics Of The Nonlinear Theory Of Traveling Wave Tube

Traveling Wave Tube (TWT) is one of the most important types ofmicrowave/millimeter wave vacuum tubes. Due to its high power, high gain, highefficiency and broadband, TWT is widely used in telecommunications, radars andelectronic warfare applications. In this dissertation, a theoretical research on the RF(Radio Frequency) characteristics of a helical Slow Wave Structure (SWS) is made.Basing on the tape-helix model, we give quantitative explanations of the effect ofdielectric loss on RF characteristics and an analysis of the attenuator-coated helicalSWS. We also implement and improve the simulated annealing algorithm into 1DCHRISTINE to optimize the electronic efficiency in a helix TWT in which the helixpitch varies.The work and innovations of this dissertation are listed as follows:1. A general theory is developed to account for the effect of the dielectric lossarising from discrete rods on the RF characteristics in an actual helical slow wavestructure (SWS). The effect of the lossy dielectric rods has been studied on severalpropagation parameters, namely, phase propagation constant, interaction impedance andattenuation constant at different operating frequencies.2. An electromagnetic analysis of the RF characteristics of a helix withattenuator-coated dielectric supports is made. Basing on the rigorous tape-helix modeltaking into account the space harmonics, the analysis improves an earlier study on ahelix fitting in a continuous dielectric tube in an overall metal envelope and predicts theattenuation constant, the phase propagation constant, and the interaction impedanceversus the coating surface resistivity at different operating frequencies. The resultsobtained by the present tape-helix model also are validated against typical reportedexperimental results, however, with reference to the special case of no attenuatorcoating. In the meantime, a new attenuation models is set up to input the RFcharacteristics of the helical SWS in the attenuator region into a nonlinear simulation ofa helix TWT to predict the performance of the TWT more accurately.3. Simulated Annealing Algorithm which is a global optimization algorithm for functions of multi continuous variables is introduced. In order to optimize the electronicefficiency of a helix traveling-wave tube in which the helix pitch varies, we implementand improve the simulated annealing algorithm into 1D CHRISTINE, which is aparametric helix TWT code, and optimization results are shown, too.