Zhu Xiaofang

Application and validation of the TWTCAD integrated framework

TWTCAD integrated framework is a suite of helix TWT design software. It is composed of five software and interface specification between software. It includes: FemGun, a 2D gun software based on finite element method; HelixCT, a 2D helix circuit cold test software; BWI, 1D & 2D & 3D large signal software; MDCollector, a 2D multistage depressed collector design software; fPPM, magnet design software. It has been validated against some TWTs and applied in microwave tube industry.

A Correction Method for Analysis of Inhomogenously-Loaded Helical Slow-Wave Structures

In the theoretical analysis of cold-test characteristics for inhomogenenously-loaded helical slow-wave structures, a correction method is suggested to compensate the field non-uniformity during one helix period, in which an effective helix outer radius is adopted instead of the real helix outer radius. The theoretical predictions with and without correction are both compared with MAFIA simulation results and the illustrations have proved the validity of the correction method

Tests of HFCS-I on calculation of attenuation characteristics of high-frequency circuits

Using HFCS-I and MAFIA, a cubic resonator and a typical helical slow-wave structure are simulated and the quality factor of the cubic resonator and the attenuation constant of the helical slow-wave structure are stressed. The results from HFCS-I and MAFIA simulation are compared in detail and they are found to be in quite agreement. Therefore, the capability of HFCS-I on calculation of high-frequency parameters, especially the attenuation characteristics of high-frequency circuits is proved.

A 2D Electron Optics System Code for Millimeter Wave Traveling-Wave Tubes

To improve the performance of the electron optics system for millimeter wave traveling-wave tubes, we developed a two-dimensional electron optics system design tool. It includes UESTCGun, UESTCPPM and UESTCMDC to model and simulate electron guns, periodic permanent magnetic focusing systems and multi-stage depressed collectors respectively. The physics models and implements of UESTCGun code, UESTCPPM code and UESTCMDC code will be presented.

A 1-D Multifrequency Non-Linear Model and Simulation for MMW Helix TWTs

A 1D multifrequency non-linear model of the beam-wave interaction in a millimeter wave helix TWT is described. Taking consideration of the voltage depression, this model has been implemented in a code which contains the functions of scanning beam voltage and input power, convenient for the simulation of the interaction of beam and wave. A MMW TWT interaction is simulated by the code, the results from the code and the comparison with measurements are shown favorably.

Study of Novel Helical Slow-Wave Circuits for Millimeter Wave TWTs

Using simulation code MAFIA, three novel helical slow-wave structures (HSWSs) with diamond as support material are studied and then are suggested to improve the performance of a Ka-band millimeter wave TWT. The nonlinear analysis is carried through using BWI module in TWTCAD integral framework and the results have been found to be consistent with the expectation

Recent Developments to TWTCAD Integrated Framework

Recent developments to TWT Integrated Framework, a 2D modeling and simulation code suite for traveling wave tube, are presented. Two codes, UESTCPPM and UESTCDB, are added to TWTCAD. Existed another four codes are improved. TWTCAD is applying and validating in microwave industry

Parallel computing for helix TWT

Designing an octave bandwidth helix TWT for phase and gain matched operation in the EHF region presents many obstacles, the dimensional controls which must be imposed in the design and fabrication of parallel operating are difficult. Parallel computing offers the possibility to evaluate the effect that slow-wave structure parameter and operating parameter variations, such as manufacturing tolerances, this enables manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT. Computation of beam and wave nonlinearly interaction should cost many time. For analyzing the gain and phase matched characteristic, parallel computing is necessary.