在高增益、高效率的螺旋线型行波管的研制中,需要有电压驻波此极低的短衰减器。例如,若具有60分贝小信号增益的行波管的热电压驻波比必须保持在2:1以下,则此管用的衰减器的电压驻波比不得超过1.02:1。通过下述方法达到一个极低的衰减器电压驻波此是没有困难的:将碳涂在螺旋线的支持杆上,涂 In the development of high gain and high efficiency helical traveling wave tube, there is a need for a very low short attenuator with voltage standing wave. For example, if the TWTC of a TWT with a small signal gain of 60 dB has to be kept below 2: 1, the voltage standing-wave ratio of this attenuator should not exceed 1.02: 1. It is not difficult to achieve an extremely low attenuator voltage standing wave by applying carbon to the spiral support rod