Research On RF Characteristics And Nonlinear Beam-Wave Interaction In Helix TWTs

In this dissertation the RF characteristics and nonlinear beam-wave interaction of the helix Traveling-Wave Tubes (TWT) are studied by theoretical calculation, computer simulation and experiments. Multi-Objective Genetic Algorithms (MOGA) are applied in the parameters optimization of the helix. These achievements serve as a platform for the design of the helix TWT. According to the intrinsic order, the organization of this dissertation is as follows. Firstly, the basic theory of helix slow-wave structure (SWS) are studied. The reliable Cold-Test parameters supplied for Large-Signal Simulation are also obtained by computer simulation and experiments. Secondly, the nonlinear field theory is given and the parameter code is developed. They are applied to the practical design of L-band, C-band and Ku-band Space TWTs. The results of calculation and experiment agree to good accuracy. Finally, Multi-Objective Optimization Algorithms are introduced into the design, and some improvements on these algorithms are achieved. The important and creative results are listed as follows.1. The coordinate transformation of tape helix with finite width is studied indetail. The special meaning of the complex variableK_Hz - θ is pointed out, and it isdemonstrated that the appropriate coordinate transformation is the sufficient condition for separation of variable form of electromagnetic field. Making use of impedance matrix, the boundary conditions on the helix is expressed by the electric field components. It is the mathematic basis of the theory that the surface current density distribution on the tape is expanded in Chebyshev polynomials.2. For the profile of surface current on the helix tape is not measurable, the...