1.引言当某些高功率行波管工作在慢波线路的满功率电平时,返波振荡是很麻烦的事情。为了避免出现这些振荡,这些管子通常要降低性能运用。已经用来改善管子效率的渐变螺旋线,也可以同时用来改变寄生的返向空间谐波。事实上,如果渐变可以大大地增加起振电流,那末, 1. Introduction When some high power TWTs work at full power level of a slow-wave line, backwave oscillation is a very troublesome thing. To avoid these oscillations, these tubes are usually used to reduce performance. Gradient helixes, which have been used to improve tube efficiency, can also be used to alter parasitic return space harmonics. In fact, if the gradient can greatly increase the starting current, then,