带状螺旋线研究中的坐标变换

Coordinate transformation in the study of tape helix

分析了带状螺旋线行波管中电磁场分量在柱坐标系下的Floquet形式,证明适当的坐标变换是电磁场分量写成变量分离形式的充分条件.螺旋带平面展开后,应用坐标变换得到的电磁场分量变量分离形式是去除面电流分布假设的理论基础.计算并分析了一个典型结构的色散和耦合阻抗,计算结果与实验结果有很好的一致.

The Floquet form of electromagnetic field in travelling wave tubes with tape helix is analyzed in the cylindrical coordinates frame. The study showed that appropriate coordinate transformation is the sufficient condition for separation of variables of electromagnetic field. The separation of variables under the coordinate transformation is the basis of the theory in which the assumption about the surface current density distribution of the tape is avoided. The dispersion and coupling impedance of a typical structure are calculated. The computed and measured results agree with high accuracy.