具有螺旋内筒和螺旋外筒的Blumlein线

提出了具有螺旋内筒和外筒的同轴Blumlein线的结构。采用横电磁波传输理论分析脉冲形成过程，该结构具有传统Blumlein线内外线独立传输的典型特征，给出了特征阻抗、慢波系数等参数的表达式；原理实验输出脉冲顶部平坦，顶宽占半宽的80%，输出辐值和半脉宽与理论计算基本一致，验证了该结构产生长脉冲的可行性；指出了该结构容易受周围环境导体的影响，外部环境导体距离越远对脉冲输出的影响越小，在螺旋外筒底部与接地导体平板之间填充铁氧体磁芯，可把两者距离从500 mm缩减至100 mm。

Coaxial Blumlein line with spiral inner and outer cylinders

A coaxial Blumlein line with a spiral inner and a spiral outer cylinders is proposed in this paper. The pulse forming process for this line is analyzed via the transmission theory of transverse electromagnetic wave. It is found that the electromagnetic wave can transmit independently in the inner line and in the outer line which is the same as that for the conventional Blumlein line. The analytical expression for the parameters such as the wave impedance and the slow-wave coefficient are presented. The proof-of-principle experiments are also conducted, which show that the top of the output pulse is flat and is about 80% of the full width at half maximum (FWHM). The experiments also show that the amplitude and the FWHM of the output pulse are in line with the theoretical values, which verifies the feasibility to produce long pulse with this type of line. The weakness of this type of line is that it tends to be affected by the peripheral environmental conductors. When the distance between the peripheral environmental conductors and the Blumlein line gets longer, this unfavorable effect is weaker. By placing a ferrite core between the bottom of the spiral outer cylinder and the ground flat conductor, the distance between them can be decreased from 500 mm to 100 mm.