Secmotron—A new kind of high efficient micro wave tube

Secmotron (sector beam deflection modulation tube) is a new kind of high efficient microwave tube which is developed on the basis of gyrocon, The principle of gyrocon has been analyzed and it manifests that to increase circuit efficiency is necessary for improving the properties of gyrocon. One of the key points is to increase its perveance. An idea about sector beam is proposed to reduce the effect of space charge. Also the concept and construction of transforming a column beam to a thin sector beam are presented. The numerical calculation of some specific structure demonstrates that the above idea is realizable. This project is supported by NSFC     

扇调管一种新型高效率微波管

扇调管(扇形电子束偏转调制管)是在偏调管(gyrocon)基础上发展起来的一种高效率微波管。木文分析了偏调管的基本原理及其限制,指出改善偏调管的性能必须提高其线路效率。本文论述了提高导流系数是其关键之一,从而引出了扇形束的设想以减弱空间电荷效应,并提出了使普通圆柱形电子束变成扁平的扇形束的基本概念和结构。最后给出了对具体结构进行数值计算的结果,表明以上设想是可行的。     

扇调管输出环形腔的研究

扇调管是在偏调管基础上发展起来的一种高效率微波管。它的导流系数比偏调管的高,有可能工作于较低的束电压。相应地,它的输出腔则采用有双脊截面的环形腔。本文采用近似方法对这种环形腔进行了分析,详细介绍了它的设计及优化方法。最后,给出了模型腔的测试结果。它与理论计算基本吻合。     

一种实波束扫描雷达回波建模方法

提出一种实波束扫描雷达前视成像回波建模方法。使用实波束扫描实现雷达平台正前视区域二维高分辨成像。根据雷达波束掠过成像扇区的时间先后关系,将成像扇区方位向回波数据表征为天线主瓣波束采样序列与目标反射率分布函数沿成像扇区方位向采样序列之间卷积的形式。最后,通过仿真数据验证了本建模方法的有效性。     

铜蒸气激光器的热设计

本文系统阐述了铜蒸气激光器的设计过程.在大量实验资料的基础上,给出了激光器放电管尺寸、输入功率密度的选择原则,通过分析放电管内气体温度分布、激光管径向热导损耗,建立了一套确定保温层厚度的方法.分析了光束"黑心"的原因,进而提出了解决途径.以上的设计思想在我们新近研制5W器件上得到验证.     

Small-signal analysis of the helitron oscillator

In this paper, a small-signal analysis of a microwave oscillator discussed by Watkins and Wada¹is presented. This tube, the helitron, has an electron beam describing the trajectory of a helix between two concentric cylinders. Interaction is with a TEM mode supported on the inner cylinder, and the beam is focused by having a potential difference between the cylinders. This has been termed anE-type tube. TheE-type tube had originally been conceived as a device for exchanging electron potential energy of an electrostatically focused beam for RF energy. In this manner, one would expect to obtain the high efficiencies associated with anM-type tube, without requiring a magnetic field. Watkins and Wada presented experimental results in their paper, and they indicated that the theory that had been developed did not predict the observed behavior. In particular, it was stated that if the propagation constants were those of anM-type tube, the measured starting current would be one-fiftieth of the theoretical starting current. The small-signal analysis of theE-type tube developed in the main body of this paper has yielded two interesting results: 1) The electrons bunch along the direction of rotation, and lose kinetic energy. In this sense theE-type tube behaves similar to theO-type oscillator. Electron motion transverse to the dc path, which is important in theM-type tube, is not important forE-type operation. 2) Space charge forces tend to increase the bunching along the direction of rotation. This results in a negative value for the space-charge parameter, and an attendant reduction in starting current. Growing waves can exist on an electron beam that is electrostatically focused between two conducting cylinders, even without the presence of a circuit field. In this sense theE-type oscillator is similar to theM-type tube.     

Effect of electron lenses on beam noise

Some types or electron guns used to form the beam of a low-noise beam type microwave amplifier (e.g. traveling-wave tube) impress sharp potential discontinuities or velocity jumps on this beam. These discontinuities produce strong electrostatic lenses. This paper presents a theory supported by experimental results, showing that the effect of such lenses is to increase the beam noise. Further, axial magnetic fields are shown to reduce this undesirable effect.     

迴旋管和相对论性器件在苏联的新发展

本文介绍了迴旋管和相对论性器件在苏联的发展趋势和目前达到的水平。文中较详细地介绍了相对论性速调管、切伦柯夫振荡器、偏调管和迴旋管等目前达到的新水平以及它们的应用     

Effects of high-velocity secondary electrons in traveling-wave tubes

The presence of a beam of high-speed secondary electrons in a traveling-wave tube affects the amplification and cross-modulation characteristics of the tube. When primary electrons strike the collector electrode, secondary electrons are produced. The high-speed secondary electrons have a velocity approximately equal to the primary electrons and can form a reverse beam which serves as a feedback mechanism within the traveling-wave tube. Coupling of the signal to the reverse beam and the influence of the reverse beam on the forward amplification system are investigated. The principal effects of this secondary beam are that a second-order fluctuation is superimposed on the usual variation of gain as the helix voltage is varied, and that the cross-modulation characteristics of the tube are materially altered, with the possible production of "negative" cross modulation. Experimental results demonstrate the existence of these effects and indicate that they are absent when the secondary beam is eliminated.     

E波段折叠矩形槽波导行波管的研究

分析了一种适用于E波段81~86 GHz空间行波管的新型慢波结构——折叠矩形槽波导.折叠矩形槽波导来源于传统的矩形槽波导,将E面沿其纵向来回弯曲而形成.利用电磁场仿真软件Ansoft HFSS设计优化并最终确定了E波段折叠矩形槽波导的关键几何尺寸.同时,模拟仿真出了折叠矩形槽波导在中心频率f=83.5 GHz处的耦合阻抗沿x和y方向上的变化趋势,得出其可通过加载带状电子注获得更高的平均耦合阻抗.利用CST粒子工作室模拟得出:折叠矩形槽波导行波管在中心频点83.5 GHz处输出功率为210 W,电子效率达到8.05%.     

A Novel Wideband Subarray Technique for Shaped Pattern Generation and Adaptively Interference Rejection

In this article, a simple and efficient technique for the wideband shaped beam and sector beam pattern generation with their adaptive interference rejection is proposed. A microcontroller controlled and time delay based beam forming network for simultaneously generating multiple beams, shaped beam and sector beam is conceptualized. The antenna patterns considered here is formed by linear array of isotropic elements grouped as subarray. The shaped and sector beam synthesis procedure is practically simplified by simultaneous adding the constituents beams from the subarrays, was theoretically established by Woodward and Lawson (Proc. IEE. 95(1):362–370, 1948). Apart from the shaped beam generation a technique for adaptive interference rejection in shaped patterns using combination of time delay and phase shifter is discussed. This topic promises good prospect for wideband pattern generation and interference rejection.     

激光推进环聚焦数值模拟研究

设计了激光推进环聚焦系统,在考虑入射激光束与光船聚焦系统主轴偏离情况下,建立研究环聚焦性能的数学模型,并数值模拟研究了环形"点火"线的形状、大小、能流密度以及点火区域空间特性.数值分析结果表明:环聚焦系统在喷管内产生半径约为49 mm的环状点火区域,比点聚焦产生的点状点火区域要大一个数量级,从而使吸收室内工质加热更加均匀;当激光束从垂直入射到偏离入射变化时,聚焦能量不再均匀地分布在圆形环线上,而是向x轴聚积,整个点火区域呈扁环状,因此,近椭圆柱状喷管设计将极大地提高激光能量转换效率.     

Prebunched beam traveling-wave tube studies

A traveling-wave tube with a prebunched beam is found to have a considerably higher efficiency than the same tube without prebunching. For the particular tube tested the efficiency is increased from 20 to over 35 per cent at a gain of 8. Computer calculations using a discrete disk model give similar results. The beam is bunched tightly in energy at the position of highest efficiency, indicating that very high efficiency could be obtained with a depressed collector. Both current and velocity modulation are required for prebunching, and are obtained by means of a current grid followed by an inductively tuned velocity modulation cavity. The requirements of the current grid are not great so that operation should be possible at frequencies well above the normal operating region of a microwave triode. The operation of the tube is sensitive to the output match, and it appears to be difficult to obtain a good match with the beam on.     

Large signal behavior of high power traveling-wave amplifiers

The results of an experimental investigation on the large signal behavior of a kilowatt power level helix type traveling-wave amplifier tube are presented. Operation with and without attenuators was investigated using a movable electromagnetic probe to measure power level along the tube. Quite different effects of drive power and beam voltage on the saturation level were found for operation with and without attenuators. The maximum power level is lower for attenuator operation. Also, power levels do not continue to increase with increasing beam voltage and drive power. In contrast, attenuator-less operation produces the highest efficiency, and the power levels continue to rise with increasing beam voltage and drive power. Conversion efficiencies as high as 25 per cent are obtained with an attenuator and as high as 40 per cent without an attenuator. Efficiency calculations based on small-signal theory can be made to agree reasonably well with the experimental attenuator-less operation efficiencies by assuming an appropriate ratio of the ac component of beam current to the dc component of beam current, i/I0.     

Soft X-ray effects upon silicon-diode arrays aged in camera tubes

The rate of dark current increase of silicon-diode-array camera- tube targets has been found to be as high as 10 nA/h when operated with electrode potentials as high as 1000 volts. Irradiation of the target by soft X-rays is shown to cause the fast-state density at the silicon-silicon dioxide interface to increase. The increased fast-state density is largely responsible for the increased dark current. The X-rays are generated by the impact of the returning electron beam upon high-potential tube electrodes. Several means for reducing the X-ray flux at the target are discussed. The most effective means is a reduction in tube electrode potentials to low values where dark current aging rates as small as 0.001 nA/h have been achieved.     

The cycloidotron, a proposed crossed-field, fast wave millimeter tube

In general, the electrons of an electron beam in crossed electric and magnetic fields move in cycloids. The possibility of using such a beam in harmonic operation of a periodic-beam fast-wave tube has been explored. The most promising tube of tiffs type for a millimeter generator is one in which the ac motion occurs along the dc magnetic field and consequently is transverse to the dc motion. The small signal analysis of this tube is given, neglecting space charge, and it is shown that for reasonable beam currents backward wave oscillations at twice or even three times the cyclotron frequency can be obtained. The analysis is made particularly simple through the use of the small signal power theorem. Some of the practical problems associated with this tube are briefly considered.     

磁选态和光抽运铯束管特性的对比

简述了磁选态和光抽运铯束管的工作原理，在频率准确度、短期稳定度、长期稳定度三个方面将两者对频标性能的作用影响进行了计算对比。结果表明磁选态管准确度和长稳较好，短稳有限；光抽运管可使优值系数F增大数倍，短稳有优势，但光频移影响了准确度及长稳，应尽力减小。两者各有长处与不足，未来发展趋势将是一方面继续改进磁选态管，另一方面应发展完善光抽运管。     

面向无人机毫米波高效波束搜索的码本优化设计

针对无人机(UAV)动态环境下,波束无法实时匹配这一问题,结合毫米波数字-模拟混合波束形成系统,提出采用一种低复杂度的码本设计方法,以提高波束搜索效率。该方法首先建立了分层波束搜索模型并提出以扇形波束作为训练波束;其次将扇形波束的阵列响应改写为傅里叶级数形式,并利用傅里叶反变换得到扇形波束的理想数字码本;最后通过几何贪婪(Greedy Geometric, GG) 算法设计数字基带预编码器和射频预编码器,得到了具有快速搜索能力的优化波束。仿真结果表明,该码本优化方法具有较低的复杂度,有效地提高了波束搜索效率,满足了无人机实时波束匹配需求。     

Velocity and current distributions in the spent beam of the backward-wave oscillator

Results are presented of an experimental study of the spent beam of a backward-wave oscillator. The instantaneous velocity and current of the spent beam are measured using a velocity analyzer built onto the collector of a scaled 80-mc backward-wave oscillator. The tube employs a sheet beam and interdigital line, 12 feet long. It is designed to be representative of large-space-charge tubes. The measured trajectories of the spent beam are examined to deduce the mechanism of interaction between the beam and the circuit along the whole length of the tube. It is deduced that the level of oscillation is determined by nonlinear effects in the convection current. Finally, the RF output efficiency saturation at high beam currents is found to be caused by electrons which fall back in phase from a retarding to an accelerating circuit field.     

Experimental Investigation of a Novel Circuit for Millimeter-Wave TWTs

A novel folded waveguide circuit that features thick iron pole pieces with hollow centers was built as part of a periodic-permanent-magnet-focused W-band single-stage test-vehicle traveling-wave tube (TWT). These hollow centers, which comprise part of the slow wave circuit, increase the rms axial field and significantly reduce the unwanted transverse field imbalance. For this TWT, a tetrode gun that creates an ultralaminar 20-kV 0.25-A nominal electron beam was used. It was demonstrated that this gun and magnetic structure can provide greater than 97% beam transmission for peak beam power levels as high as 9.25 kW (25 kV, 0.37 A). The unplated circuit, operating around 91 GHz on the edge of a passband, exhibits between 10 dB and 12 dB gain that compares favorably with results of device modeling utilizing the 3D particle-in-cell code Magic3D. Using a feedback approach to characterize large-signal operation, the tube generated 40 W of regenerative oscillator power. Design-optimized versions of this circuit show promise of enabling W-band TWT amplifiers that provide up to 300 W of peak RF output power