MAFIA计算螺旋型回旋行波管色散特性

 为了给回旋行波放大器中螺旋管的设计提供一种简单易行的计算和优化方法，构建了特定的螺旋型回旋管模型，并用色散特性方程和MAFIA软件计算了其色散特性。采用MAFIA软件计算时，由于周期条件，相移从-180°到180°，每30°计算一次，对应的传递常数从-0.837 8 cm ^-1 变化到0.837 8 cm ^-1 。由于在准周期条件中相应的相移对应相应的传递常数，求解出对应的基模频率，通过模式识别，得出耦合以后的模式频率，即可以得出色散曲线。结果表明：在8.3～10.6 GHz的工作频率范围内，两者的计算结果吻合较好，相对偏差小于0.5%。色散曲线趋于斜率为正的直线，该特性说明了螺旋型回旋行波管具有较高的工作效率和较宽的带宽。

Computation for dispersion of gyro-TWT with a helical waveguide by MAFIA

This paper provides a simple technique to design and optimize the spiral waveguide of Gyro-TWT. The dispersion characteristics of helical waveguide was given out. The structure of waveguide was modeled by CAD and it′s dispersion curve was calculated by MAFIA using quasi-periodic boundary condition. The modes were calculated alternation 30° phaseshift from -180° to 180°. This method leads to a good agreement with the result of dispersion equation over 8.3~10.6 GHz, and the maximum relative deviation is below 0.5%. For a rather broad frequency band around the point where the longitudinal wavenumber is equal to zero, the slope of the dispersion curve trends to a positive constant. As a micro-wave amplifier, Gyro-TWT using spiral waveguide has a good potential in improving its effectiveness and increasing its bandwidth.