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本文描述研制在7.5—11.5千兆赫频段中最大功率约1千瓦,增益大于30分贝的脉冲行波放大管中碰到的一些困难。这一功率电平比英国过去用螺旋型管试过的要高得多。本文只介绍研制工作的一部分,一般只谈由于高功率、高频率与宽频带三者俱备而引起的困难。行波管要宽频带就必须用螺旋线电路。这就造成设计的限制,要限制工作电压以避免返波振荡。因而可以得到的最大功率受到限制,即使是在脉冲情况下,当频率增加时功率也要变小。在X频段波导耦合高功率脉冲行波管的实际设计中,发现必须保持较小的外径,这就造成较小的介质负载因数,适当选择丝径并控制玻壳壁厚可以使它增大**。已经研究出一种简单的耦合结构,在7.5—11.0千兆赫范围内给出小于1.5的电压驻波比,衰减器匹配良好,并且在同一频带中具有实际上不变的衰耗。在运用中,用远高于同步电压的工作电压,减少返波振荡的危险性。从最后的管子中,在30分贝增益时得到1千瓦的脉冲输出功率。亦会观察到高达50分贝的小信号增益。
This article describes some of the difficulties encountered in developing a pulsed traveling wave amplifier with a maximum power of about 1 kilowatt and a gain greater than 30 dB in the 7.5-11.5 GHz band. This power level is much higher than what Britain tried with spiral pipes in the past. This article describes only part of the development work, generally only due to high power, high frequency and broadband are all three difficulties caused. Traveling wave tube to the broadband must use the spiral circuit. This creates a design limitation that limits the operating voltage to avoid backwashing. Therefore, the maximum power that can be obtained is limited, even in the case of a pulse, the power becomes smaller as the frequency increases. In the actual design of the X-band waveguide-coupled high power pulsed TWT, it was found that the smaller outer diameter must be maintained, which results in a smaller dielectric loading factor. Appropriate selection of the wire diameter and control of the bulb wall thickness can increase it **. A simple coupling structure has been developed that gives a voltage standing wave ratio of less than 1.5 in the 7.5-11.0 GHz range, good attenuator matching, and virtually invariant attenuation in the same frequency band. In use, with much higher than the operating voltage of the synchronous voltage to reduce the risk of return wave oscillation. From the last tube, one kilowatt of pulsed output power was obtained at 30 dB gain. A small signal gain of up to 50 dB is also observed.