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从设计返波管的观点出发,螺旋线结构上的返波阻抗是Em~2/2Bm~2P。介绍了单螺旋线及双螺旋线的阻抗一ka(周界与自由空间波长之比)曲线。讨论了薄带与圆导线二种情况。阻抗曲线是根据导体表面高频电流实际分布的近似式来计算的,所用的近似式在跟特定的ka值之精确解作比较后得到证明。文中提出了一个证据,它证明了假使一个螺旋带(tape helix)的间隙等于另一个螺旋带的带宽,则两者的返波阻抗相等。推导了介质支持器对返波的阻抗和速度之影响的表示式。
From the viewpoint of designing the back-wave tube, the return wave impedance on the helical structure is Em ~ 2 / 2Bm ~ 2P. The curves of the impedance of a single helix and double helix (a ratio of perimeter to free space wavelength) are introduced. Discussed both the ribbon and the round wire. The impedance curve is based on an approximation of the actual distribution of the high-frequency current on the surface of the conductor. The approximation used is evidenced by comparison with the exact solution of the specific ka value. In this paper, we present a proof that the back-wave impedances of the two are equal, provided that the gap of one helical band equals the one of the other helical band. The expression of the influence of the media holder on the impedance and speed of the return wave is deduced.