【作者】 陆德坚；

【导师】 刘濮鲲； 王自成；

【作者基本信息】 中国科学院研究生院（电子学研究所） ， 物理电子学， 2007， 硕士

【摘要】 本论文结合中国科学院电子学研究所正在开展的Ka波段毫米波行波管项目，从输能装置、慢波系统的色散和耦合阻抗特性、返波振荡及计算机模拟方法等方面较为系统地研究了Ka波段毫米波行波管的高频结构及其特性，并设计了Ka波段宽带输能装置和新型反绕双螺旋线慢波系统，为毫米波行波管高频结构的研究及工程实现提供可行的方案和方法支持。论文的主要工作如下：一、Ka波段毫米波行波管宽带输能装置的分析与设计。结合工程实际，分析了该输能装置设计中因结构尺寸小而遇到的问题，接着从理论上作了初步设计，提出了同轴转脊型波导转矩形波导的方案，并用HFSS对该输能装置进行仿真分析及对参数优化，以降低带宽内的驻波系数，同时兼顾降低工艺的难度，以方便工程实现，结果在26.5-40GHz带宽内驻波系数小于1.75，实现了宽带传输。二、慢波系统高频特性的仿真研究。总结并比较了理论计算、实验和计算机模拟等主要的高频特性研究方法。对计算机模拟的谐振法、准周期边界条件法、微扰法及直接场提取法等进行比较并总结其实施方法，指出直接场提取法在空间谐波和返波振荡的研究中有着独特的优点，其计算效率和精度也优于其他方法。最后用螺旋线慢波系统和休斯型耦合腔慢波结构两个例子证明了直接场提取法的准确性。三、新型反绕双螺旋线慢波系统的分析与设计。基于降低工艺难度的目的，本论文提出了一种正绕和反绕螺旋线半径不相等的新型反绕双螺旋线慢波系统，并仿真分析了结构参数对色散特性及耦合阻抗特性的影响。结果表明：耦合阻抗在螺旋带内半径较大时没有明显下降；减小螺旋线宽度有利于降低相速度和提高耦合阻抗；在一定范围内，相速度随螺距的减小而增大。在这基础上，为8 mm行波管设计了新型反绕双螺旋线慢波系统，达到了降低工艺难度，提高基波耦合阻抗，增强抑制返波振荡的能力，展宽带宽及降低对电子光学系统的要求等目的。四、毫米波行波管返波振荡的仿真研究。研究了Ka波段毫米波行波管的螺旋线、反绕双螺旋线、新型反绕双螺旋线及Ferruleless型耦合腔等典型慢波系统的返波振荡问题。结果表明：(1)由于夹持杆和纵向翼片加载的影响，螺旋对称性受到破坏，螺旋线慢波系统中出现非常明显的角向谐波次数和轴向谐波次数不相等的空间谐波分量；(2)螺旋线慢波系统万模对应的归一化频率(kα)较小，在π模附近，有产生返波振荡的危险；(3)反绕双螺旋线慢波系统抑制返波振荡的能力大大增强，在Ka波段基波耦合阻抗提高约54％，负一次返波阻抗减小，可以工作的归一化频率(kα)提高了约一倍，而新型反绕双螺旋线慢波系统的返波振荡抑制能力与反绕双螺旋线的基本一致；(4)为了避免返波振荡，Ferruleless型耦合腔慢波系统的工作频带的选择应远离单腔相移为π，2π的频点。五、准周期边界条件法在耦合腔结构高频特性研究中的应用。指出准周期边界条件法在耦合腔高频特性研究的应用中会出现的伪解，提出相移法和能量法对伪解进行辨别，并初步探讨了产生伪解的原因，然后提出了去除伪解的理论分析法和相移法，其中相移法具有普遍性。最后给出了休斯型耦合腔的算例作为例证。为准周期边界条件法在耦合腔高频特性研究中的应用铺平了道路。更多还原

【Abstract】 In this dissertation, the RF characteristics of Ka-band millimeter-waveTraveling-Wave Tubes (TWT) are studied systematically on the topic of dispersionand impedance of Slow-Wave System (SWS), Backward Oscillation (BWO) andcomputer simulation investigation method. Also, the wide-band output coupler ofKa-band millimeter-wave TWT and novel contrawound helix SWS have beeninvestigated and designed in this dissertation. The research provides supports to theinvestigation and project implement of millimeter-wave TWT. The important andcreative results are listed as follows.1. Investigation and design of wide-band output coupler of Ka bandmillimeter-wave TWT. The difficult of the design of output coupler which causes bythe small dimension is analyzed, according to the need of project implement. Then,first design was finished in theoretical, presenting the design of coaxial cable todouble ridge waveguide to rectangle waveguide, and HFSS was used to optimize andinvestigate the dimension of the structure for minimizing VSWR. The results showthat VSWR＜1.75 in the band 26.5-40GHz, and the requirement on technologicprecision is brought down. The goal of wide-band transform is accomplished.2. Simulation investigation of RF characteristics of the SWS. The researchmethods on RF characteristics, including theory calculation, experiment and computersimulation, are summarized and compared. Then the resonance method, quasi-periodboundary method, perturbation method and direct field extraction method of computersimulation methods for RF characteristics are compared and summarized, pointing outthat direct field extraction method is convenient to get the whole RF field of SWS, which plays a key role in the investigation of BWO and space harmonics,3. Investigation and design of novel contrawound helix SWS. A novelcontrawound helix slow-wave system with different helix radius is presented toreduce the difficulty of manufacture. CST MWS is used to simulate and investigatethe influence of dimension on the dispersion and interaction impedance. The resultsshow that the radius of contrawound helix can be larger than that of helical withoutcausing a sharp decrease of interaction impedance and the decrease of tape width helpbring down the phase velocity and improve the interaction impedance. The resultsalso indicate that, in certain range, the reduction of pitch increase the phase velocity.Finally, a design of the SWS is done for 8 mm millimeter-wave TWT, the interactionimpedance is improved, and the risk of BWO is low. Also, the requirement on electronoptics system is brought down because of large electron path radius, and theintroduction of longitudinal vane loads is a great help for the band-wide of the TWT.4. Simulation investigation of backward wave oscillation of millimeter-waveTWT. HFSS was used to simulate helical, contrawound helix, novel contrawoundhelix and ferruleless coupled-cavity slow-wave system, which work in Ka-band, toinvestigate the backward oscillation of millimeter-wave traveling-wave tube. Theresults show that, in helical slow-wave system, space harmonics, which axial spaceharmonic number and azimuth space harmonic number are unequal, are evident, andthe SWS runs the risk of backward oscillation around theπmode. Relatively,contrawound helix and novel contrawound helix show excellent ability in restrainbackward oscillation by improving interaction impedance and the normalizedfrequency which can work without the risk of BWO. And ferruleless coupled-cavitycircuit will run the risk of BWO when phase shifts per cavity areπor 2π.5. The application of quasi-period boundary method on the study of RFcharacteristics of coupled-cavity structure. The dissertation points out that the fakesolutions appear when the quasi-period boundary method is applied on thecoupled-cavity structure. Phase method and energy method were presented to identifythe fake solutions. Then, the cause of fake solutions is made out. Theory analysis andphase method were presented to eliminate the fake solutions. Finally, the application of the method on Huges coupled-cavity structure was carried out as an example. Thestudy is a great help for the application of the method on RF characteristics ofcoupled-cavity structure.更多还原