谈谈电视微波中继设备维护中的几个技术问题

一、反射速调管反射极电压电路在反射速调管电源中,为满足速调管的最佳工作状态,对反射极电压的调节范围有一定的要求。K-201速调管阴极电压U_K=-750伏时,最佳工作区中心点出现在反射极电压U_R=     

三角晶格金属柱PBG谐振腔的设计

随着回旋管向高频发展,高次谐波互作用研究成为重要方向。当普通回旋管工作在高次谐波时,效率很低,尤其是模式竞争问题很难解决。因此,必须改进结构,才能有效地实现高次谐波互作用。而光子晶体结构恰恰能对非工作模式实现有效的抑制。介绍了一种新的光子晶体谐振腔设计方法并成功设计出一个工作于高次模式下单模传输（TM01）的三角晶格金属柱PBG谐振腔。进一步改进后得到了一个工作在Ka波段的光子晶体谐振腔。该结构能应用于目前项目研究,具有工程价值。     

栅控反射极反射速调管

一、引言反射速调管的反射极调制灵敏度可由以下繁琐形式来表示: Δf/ΔV_R=πNf_0/(Q_L-πN)(V_B+|V_R|) 式中: N为反射极电压模式,即2 3/4,3 3/4……。 f_0为工作频率。 Q_L为谐振腔的有载品质因素。 V_B为电子注或谐振腔电压。 |V_R|为反射极电压的绝对值。上式证明,当采用高的谐振腔有载品质因素或运用高的电子注电压和最低可应用的反     

W 波段平面线形排列多注速调管谐振腔的研究

本文通过三维仿真软件CST-MSW 建立了W 波段平面线形排列多注速调管五间隙谐振腔的物理模型,分析了其 某些参数尺寸变化对场形的影响,并与带状注五间隙谐振腔相关特性进行了对比分析,验证了该模型相对于带状注速调 管谐振腔在场形稳定性方面的优点。该型谐振腔在传统带状注速调管谐振腔的基础上发展而来,在避免了带状注速调管 电子注传输过程中的缺陷的同时,又继承了带状注速调管相对于传统单注速调管的一些优点。     

Ka波段AlGaN/GaN HEMT栅结构仿真研究

为了研究适合Ka波段AlGaN/GaN HEMT的栅结构尺寸,借助二维器件仿真软件Silvaco Atlas,在完善仿真模型的基础上研究了Γ型栅各部分对AlGaN/GaN HEMT特性的影响,包括栅长与短沟道效应的关系、栅与沟道距离对短沟道效应和饱和漏电流的影响,以及栅金属厚度对fmax,栅场板对fT、fmax和内部电场的影响。根据典型器件结构和材料参数的仿真表明,为了提高频率并减轻短沟道效应,栅长应取0.15～0.25μm;减小栅与沟道的距离可略微改善短沟道效应,但会明显降低器件的饱和漏电流,综合考虑栅调制能力、饱和漏电流、短沟道效应三个方面,栅与沟道距离应取10～20nm;为了提高fmax,栅金属厚度应大于0.4μm;缩小栅场板长度可有效提高器件的频率,兼顾Ka波段应用和提高击穿电压,栅场板长度应在0.3～0.4μm左右。仿真得出的器件性能随结构参数的变化趋势以及尺寸数据对于Ka波段AlGaN/GaN HEMT的研究具有参考意义。     

W波段带状注速调管多间隙腔高频结构及其特性

通过对W波段带状注速调管的哑铃型谐振腔特性进行分析,利用三维高频仿真设计软件CST-MSW建立了单间隙、三间隙、五间隙腔的物理模型,详细分析了不同结构尺寸对于高频系统相关冷参数的影响,优化得到了相应的高频结构及其特性参数,以此作为开发的二维注波互作用程序SBK.2D快速计算的高频输入参数.同时,为了结合注波互作用系统的热参数三维仿真设计,采用MAGIC-3D对多间隙腔的高频特性及参数进行了仿真计算,得到的结果与CST冷参数设计基本一致,为W波段带状注速调管注波互作用系统的设计提供了重要参数和依据.     

Ka波段GaN HEMT栅结构仿真研究

为了研究适合Ka波段GaN HEMT的栅结构尺寸,借助二维器件仿真软件Silvaco Atlas,在完善仿真模型的基础上研究了T型栅各部分对GaN HEMT特性的影响,包括栅长与短沟道效应的关系、栅与沟道距离对短沟道效应和饱和漏电流的影响,以及栅金属厚度对最大震荡频率,栅场板对截止频率、最大震荡频率和内部电场的影响。根据典型器件结构和材料参数的仿真表明,为了提高频率并减轻短沟道效应,栅长应取0.15~0.25um;减小栅与沟道的距离可略微改善短沟道效应,但会明显降低器件的饱和漏电流,综合考虑栅调制能力、饱和漏电流、短沟道效应三个方面,栅与沟道距离应取10~20nm;为了提高最大振荡频率,栅金属厚度应大于0.4um;缩小栅场板长度可有效提高器件的频率,兼顾Ka波段应用和提高击穿电压,栅场板长度应在0.3~0.4um左右。仿真得出的器件性能随结构参数的变化趋势以及尺寸数据对于Ka波段GaN HEMT的研究具有参考意义。     

Ka波段一体化收发信机设计

Ka波段一体化收发信机是无线通信系统中的重要电路,它对整个系统的噪声系数,灵敏度等关键指标起决定性作用。文中对Ka波段一体化收发信机的工作原理进行了阐述,同时给出了整机功能实现框图,分析了接收通道单元、本振单元、发射通道单元和电源控制单元共4个单元的设计方案,并给出了仿真结果与测试结果。试验结果表明,Ka波段一体化收发信机接收机噪声系数≤2.2 dB、增益≥60 dB、输入输出驻波、相位噪声杂散、镜像抑制等指标均满足技术要求。发射机1 dB压缩点功率≥30 dBm,增益≥50 dB,三阶交调,杂波抑制等均满足实用技术要求,并根据测试结果对Ka波段一体化收发信机的部分技术指标提出了进一步优化的方案。     

强耦合式带状注速调管多间隙输出腔的设计

提出了一种强耦合式带状注速调管多间隙输出腔, 并将之应用于Ka波段带状注速调管输出腔的设计. 此设计可以获得更好的输出耦合特性和理想的场形. 更重要的是, 这种结构的漂移管允许被设计为对工作频率的截止状态, 从而可以获得更理想的电场场形以利于注波互作用. 从表面电流的角度分析了这种设计的理论依据. 通过使用粒子模拟软件进行仿真, 在中心频率获得了稳定的功率输出, 互作用效率达到50%以上, 3dB带宽约75MHz.     

等离子填充扩展互作用振荡器研究

对等离子体填充扩展互作用振荡器进行了研究,通过CST软件研究了填充不同密度等离子体对Ka波段矩形耦合腔扩展互作用振荡器高频特性的影响,得到了通过改变等离子体密度与工作电压实现调节扩展互作用振荡器工作频率的方案.利用CST粒子工作室对其进行了粒子模拟分析,结果表明通过电子束电压和等离子体密度的共同调节,可使Ka波段扩展互作用振荡器实现34.14～37.99 GHz的调谐.     

Analysis of a frequency-modulated reflex klystron with minimum incidental amplitude modulation

Simultaneous modulation of the reflector and beam voltages of a reflex klystron will produce frequency modulation with minimum incidental amplitude modulation. The required variation of reflector voltage with beam voltage, for constant output power, is derived from the fundamental equations of the reflex klystron. Experimental verification of this analysis is presented. Reflex klystron oscillators which can be frequency modulated with minimum incidental amplitude modulation find application in FM Doppler radars, communications systems, and as signal sources for microwave testing.     

Discontinuities Appear in the Repeller Current of a Reflex Klystron Detector

It is known that reflex klystrons are usable as microwave detectors. When the repeller current was plotted against acceleration grid (which is anode) voltage, Koctienko, Deviatkov, and Lebed found discontinuities. Whitford did not find these discontinuities for the 726A reflex klystron. Koctienko, et al., explained that the discontinuities were attributed to the appearance and disappearance of the virtual cathode when the klystron began or stopped oscillation. Whitford explained that the beam current density of the 726A reflex klystron was sufficiently high to maintain the virtual cathode at all times.     

A low voltage one centimeter retarding-field oscillator

The retarding-field oscillator is similar in operation and applications to the reflex klystron but is simpler in structure. In this paper a new low-voltage design is described and some of its experimental characteristics are presented. These include a power output in excess of 40 milliwatts in the wavelength range 0.9-1.1 cm with an anode potential of 400 volts and a beam current of 26 milliamperes. A brief comparison is made between this low voltage retarding-field oscillator and known available reflex klystrons.     

Noise Figures of Reflex Klystron Amplifiers

The noise figure of the 2K25 reflex klystron amplifier was investigated. The noise figure of the reflex klystron amplifier depends on operating frequency, electronic impedance, circuit impedance, and operating electronic mode. Experimental results show that a noise figure of 5 db is possible under particularly carefully adjusted conditions. In order to obtain the low-noise figure, careful electronic tuning and the impedance adjustments are particularly important. Generally, relatively low noise figures were obtained when the electronic tuning was good. Noise figures of cascaded reflex klystron amplifiers were also investigated experimentally. Noise figures of the cascaded amplifier were generally higher than that of the single stage amplifier, but still low enough to use this reflex klystron amplifiers as a preamplifier of a microwave receiver to increase the sensitivity of the receiving system.     

Investigation of Millimeter Wave Reflex Klystron Amplifiers (Correspondence)

It has been shown that reflex klystrons are usable for microwave and millimeter wave amplification. The purpose of this communication is to report that a VA-99 fixed-cavity reflex klystron performed well as a negative-resistance amplifier in the "difficult" millimeter wave region and that the amplifier was operated not by loading it so that it was incapable of oscillation as has been previously reported,but by adjusting voltages and impedances so that it was on the edge of a mode of oscillation. All measurements were made using the setup shown in Fig. 1. In the amplifier section, the reflex klystron was connected to the main waveguide line with an H-plane tee with an EH tuner, each at the input and output end of the colinear arm of the H-plane tee. The repeller and anode voltages, and the circuit impedance were adjusted so that the oscillation stopped at the signal frequency.     

X波段同轴多注相对论速调管放大器模拟研究

 设计了工作在X波段的同轴多注相对论速调管放大器,建立了带输入、输出波导结构的三维整管模型,采用三维电磁粒子模拟软件对其高频特性进行了优化设计,对电子束经过输入腔后的束流调制、注入微波吸收情况、中间腔对束流的调制以及输出腔的微波提取情况进行了模拟研究.在输入微波功率为70kW,电子束束压为600kV,束流为5kA,轴向引导磁感应强度为0.6T的条件下,输出微波功率达到了1.3GW,效率为43%,增益为42dB,在较低的输入微波功率和较小的轴向引导磁感应强度的情况下,模拟实现了X波段RKAGW级的微波功率输出.     

Three-dimensional evaluation of energy extraction in output cavities of klystron amplifiers

An accurate three-dimensional analysis of the performance of output gaps in klystron amplifiers was carried out. The parameters investigated were: beam radius, perveance, output gap angle, output gap peak voltage, RF phase, magnetic field, and beam interception. A new, accurate method for computing space-charge forces between axially and radially deformable rings was developed. Rigorous expressions for electric and magnetic fields in the tunnel and the gap were used. The highest computed efficiency for an optimally bunched beam was 80.3 percent with 6 percent "ideal" interception. An important conclusion is that efficiency decreases with increasing normalized tunned radiusbeta_{e}aforb/aconstant in the examined range0.4 and probably beyond. Excellent correlation in efficiency and interception between a model klystron developed by E. Lien of Varian and the authors' program was established.     

Space-charge effects in klystrons

The effects due to the dc field of the space charge in a reflex klystron have been calculated on a digital computer. It is found that the electronic efficiency may be reduced by a factor as large as 10 under space charge conditions which may exist in a typical low-voltage tube. Small signal theories which include the effects of the dc space charge are presented for the reflex klystron and two-gap klystron amplifiers and oscillators. The small signal theory is used primarily to aid in the interpretation of the computer calculations. The theory predicts that the efficiency of the two-gap oscillator may be reduced by a factor no greater than 3.7, but that the power gain of the two-cavity amplifier may be increased by as much as 13.7. It is also found that the inclusion of space charge effects will in general require different applied dc voltages for operation at the center of the various electronic modes, as compared with the infinitesimal-space-charge conditions. Upon comparing the theoretical calculations with actual reflex klystron data, it has been found that the theory adequately explains the behavior of the power output, efficiency, and electronic bandwidth as the beam current is varied, for conditions of moderate or small space charge. For conditions of large space charge the theoretical model does not represent the conditions in an actual tube with sufficient accuracy; it is pointed out how the theory may be improved and how the present work may be useful as a starting point for further calculations.     

1kW速调管放大器控保电路的设计

根据1kW速调管放大器的特点,在阐述速调管工作特性的基础上,分析了速调管的典型外围电路,详细介绍了控制与保护项目的具体要求。为了提高速调管放大器的工作可靠性,在模拟信号取样电路中采用高电压隔离放大器和多级箝位电路等抗干扰措施。1kW速调管放大器采用二次过荷保护原理进一步提高整机的抗干扰性能。利用监控软件实现二次过荷保护功能,简化了硬件电路的设计难度,大大提高了应用的灵活性。