【作者】 张强；

【导师】 刘列； 袁成卫；

【作者基本信息】 国防科学技术大学 ， 电子科学与技术， 2012， 博士

【摘要】 随着高功率微波技术的发展，具有多个波段输出特性和更高输出功率水平的高功率微波系统越来越受到人们的重视，发射分系统作为其中的一个关键组成部分之一，在很大程度上决定着系统的方案选择。由于目前大部分成熟的高功率微波源多工作在单频段，且输出功率都有物理极限，一种可行的方案是，利用通道合成的方法将多个不同频段的微波源输出的微波进行合成和共天线向外辐射，一方面提高微波输出总功率，另一方面扩展系统输出微波频段。基于此，本文提出了一种利用正交型通道合成器和弯曲同轴传输线单元实现多管双波段高功率微波紧凑化辐射的方案。论文对系统中的两类正交型通道合成器、弯曲同轴传输线和具有同轴馈电结构的双波段喇叭天线进行了系统的理论分析、数值仿真和关键单元的实验研究，旨在探索多管多波段一体化辐射的有效途径，以期为高功率微波的实用化奠定基础。论文的研究内容主要包括以下几个方面：1、为了实现两路GW级、极化方向相互正交的X波段微波合成输出，对T形通道合成器进行了仿真设计和实验研究。通过在T形过模矩形波导内加载金属膜片控制线极化微波传输方向的方法，设计了T形通道合成器的基本结构，它所具有的行波场结构不仅有利于设计出具有高功率容量的器件，还具有结构紧凑、可工作在同一或不同频段等优点。在对该结构初步仿真分析的基础上，设计了工作中心频率为9.5GHz的T形通道合成器，并对其进行了详细的数值仿真和实验研究，结果表明：该合成器能够有效实现两个极化方向相互正交的矩形波导模单模隔离传输，单模传输效率超过95%的工作带宽为9.4GHz~10.0GHz，能够满足窄带高功率微波源的应用需求。实验结果和数值仿真分析基本一致，单通道实验获得了35ns、1.3GW的微波输出，双通道实验验证了该器件能够有效实现两路GW级X波段微波合成输出。2、为了实现两路GW级、极化方向相互正交的S波段微波通道合成，同时实现同轴端口输出，对十字形通道合成器进行了仿真设计和实验研究。通过分析同轴波导模式和矩形波导模式之间的对应关系，利用倒圆波导设计了一种十字形通道合成器，并在此基础上提出了一种改进结构。该结构具有同轴输出的特点和结构紧凑、单模传输特性好等优点。利用数值仿真和模式匹配理论对不同结构进行了分析，得到了一些有益的结论。设计了工作中心频率为3.6GHz的通道合成器，并对其进行了详细的仿真验证，结果表明：该合成器能够有效实现两个极化方向相互正交的同轴波导TE11模（Coa.TE11模）隔离传输，中心频率处单模传输效率均达到了98%，在3.5GHz~3.7GHz的频率范围内，单模传输效率超过了90%。考虑到现有大部分成熟的高功率微波源输出模式多为圆波导TM01模（Cir.TM01模），研究设计了适用于课题所需的圆波导TM01模矩形波导TE10模（Rec.TE10模）模式转换器，设计结果表明该模式转换器在工作中心频率处转换效率大于99%，在3.36GHz~3.96GHz的频率范围内，转换效率大于90%。对由模式转换器和十字形合成器组成的S波段通道合成器进行了单通道的实验研究，结果表明器件具有GW量级的功率容量，实现了模式转换和双路微波通道合成的有机统一，实验中单通道获得了32ns、1.1GW的微波输出。3、为实现高功率微波波束扫描，研究了双波段弯曲同轴传输线。为实现双波段高功率微波的波束扫描和空间指定方向发射，利用模式耦合理论对弯曲同轴波导进行了系统的研究，在此基础上首先设计了具有不同弯曲形状的单波段、双波段同轴波导模式转换器，这些器件在中心频率上的模式转换效率均达到了99%以上，实验冷测结果和数值仿真结果吻合较好。结合课题所需，对具有过模尺寸的弯曲同轴传输线进行了系统的研究，所设计的弯曲同轴波导在中心频率3.6GHz和9.5GHz处不同极化方向的TE11模单模传输效率均达到了99%，功率容量均在GW量级，其中水平、垂直极化的Coa.TE11模分别在3.05GHz~3.85GHz和2.80GHz~4.30GHz的频率范围内单模传输效率均超过95%；水平、垂直极化的圆波导TE11模（Cir.TE11模）分别在8.50GHz~10.02GHz和8.50GHz~10.50GHz的频率范围内单模传输效率均超过95%。为了满足更多波段传输需求，论文还进行了多同轴结构传输线的设计。利用模式耦合理论系统研究了弯曲矩形波导和变截面矩形波导，得到了许多有益的结论，为快速设计相关类型的矩形波导器件奠定了理论基础。4、利用变张角结构，设计了具有同轴馈电形式的双波段喇叭天线（馈源）。通过将同轴馈电结构和变张角型圆锥喇叭结合，设计了一个具有高功率容量的双波段喇叭天线，其中高频段以圆波导TE11模馈电，低频段以同轴TE11模馈电。考虑到喇叭结构的特殊性，利用模式匹配理论对喇叭结构中的典型单元和级联过程进行理论分析，进而采用口径场法对辐射口面处的多模远场方向图进行了计算。在此基础上，设计了工作中心频率为3.6GHz和9.5GHz的喇叭天线，数值仿真结果和理论计算结果吻合较好。结果表明：设计的双波段喇叭天线具有GW量级的功率容量，远场方向图达到了副瓣电平低、等化性较好的设计目标，满足应用要求。更多还原

【Abstract】 With the development of high power microwave (HPM) technologies, great effortshave been made on increasing the output power levels and the frequency spectrum ofthe HPM systems. As one of the most important sectors in the HPM system,transmission and radiation system mainly dertermines the whole structure of the HPMsystem. On the other hand, narrow-band HPM source usually operates at single bandand has limited output power at present. An alternative methd for enhancing the outputcapacity of HPM system is taking advantage of waveguide-based power combiningtechnologies, not only for increasing the output power levels, but also for the frequencyspectrum of the HPM systems. In this dissertation, detailed investigations were carriedout on multi-channel dual-band radiation system for HPM applications, and it mainlycontains two kinds of orthogonal waveguide-based power combiners, dual-band coaxialwaveguide bends and coaxial dual-band horn. The theoretical, numerical simulation andexperimental investigations shows that it is a promising method for realizingmulti-channel multi-band HPM integrative radiation, which is significant for HPM insome special applications.The detailed contents and innovative work include thefollowings:1. A specific T-junction waveguided-based power combiner is proposed forcombining the X/X band microwave beams.Two kinds of metal plates are inserted into an overmoded T-junction rectangularwaveguide, and they play an important role in controlling propagation direction oflinearly polarized microwave. The basic structure of the combiner is designed, and itstravelling wave structure is a promising merit for compact designment whilemaintaining high power handling capacity. Also, the T-junction combiner can workingat single frequency or dual-band. Moreover, based on preliminary analysis of thisstructure, a T-junction waveguided-based power combiner with the centre frequency of9.5GHz is designed. The detailed numerical simulation and experimental results showsthat, two linearly polarized microwave beams with perpendicular polarization directionshave realized power combination and transmission separately. In the range of9.4GHz~10.0GHz, its transmission efficiency exceeds95%and the corresponding bandwidthwith can meet the requirements for narrow-band HPM applications. In the experiment,the radiated microwave power is about1.3GW with pulse duration of35ns, and no pulseshortening or breakdown phenonmenon occurs.2. A cross-junction waveguide-based power combiner is investigated, realizingpower combination of S/S band microwave beams in coaxial waveguide.According to the characterstics of TE11coaxial waveguide mode (Coa.TE11mode)and TE10rectangualr waveguide mode (Rec.TE10mode), a doughnut-shaped waveguide is utilized to design cross-junction power combiner. Furthermore, a modifiedcross-junction is developed for convenience, which has coaxial output port, compactstructure and high power transmission efficiency. A prototype of this combiner isanalyzed systematically, including the mode conversion processes and the reflectioncharacteristics, achieving some valuabe conclusions. Based on the requirements, across-junction combiner with center frequency of3.6GHz is designed, and the detailednumerical simulations shows that this structure also has high power handling capacity,and two linearly polarized Coa.TE11modes with perpendicular polarization directionshave realized power combination and transmission separately. Its’ power transmissionefficiency reaches98%at3.6GHz, and exceeds90%in the range of3.5GHz~3.7GHz.In addition, HPM sources usually generate TM01circualr waveguide mode (Cir.TM01mode), a mode converter is designed to realize mode conversion from Cir.TM01mode toRec.TE10mode, which is necessary for cross-junction combiner applications. As anexample, a TM01TE10mode converter at3.6GHz is designed and simulated. It has highconversion efficiency of over99%at center frequency, and in the range of3.36GHz~3.96GHz, it is greater than90%. Experimental investigations are focused on powerhandling capacity and mode conversion effect, which shows that the combiner has highpower handling capacity with GW level, and it realizes integration of powercombination and mode conversion. In the experiment, the radiated microwave power isabout1.1GW with pulse duration of32ns.3. A dual-band coaxial waveguide bend is studied systematically for changingmicrowave propagation direction for certain purposes.To realize dual-band HPM directional transmission, coaxial waveguide bend isstudied systematically after taking advantage of mode coupling theory, obtaining thegeneral and explicit formulas of the coupling coefficients. Firstly, single-band anddual-band coaxial waveguide mode converters with different structures have beendesigned, all of them have high mode conversion efficiency of over99%at centerfrequency, and experiment and numerical simulations agree well with each other.Secondly, overmoded90°coaxial waveguide bend is proposed to meet specialrequirements. In this part, the designed overmoded90°coaxial waveguide bend notonly has high power handling capacity, but also has high pure transmission efficiency,and transmission efficiencies of TE11modes with perpendicular polarization directionsare over99%at3.6GHz and9.5GHz. In the range of3.05GHz~3.85GHz and2.80GHz~4.30GHz, respectively, their transmission efficiencies of horizontal and verticalpolarized Coa.TE11modes are greater than95%. In the range of8.50GHz~10.02GHzand8.50GHz~10.50GHz, respectively, their transmission efficiencies of horizontal andvertical polarized Cir.TE11modes are greater than95%.At the same time, multi-bandcoaxial waveguide bend with multi-coaxial structures is designed for specialapplications. Furthermore, rectangular waveguide bend and rectangular waveguide with variouscross sections are studied according to mode coupling theory, achieving many valuabeconclusions, which are theoretical foundation for quickly designing different passiverectangular waveguide components.4. Based on flare angle horn, a dual-band horn antenna with coaxial feed structureis designed for S/X band radiation.In this part, a new kind of dual-band horn antenna with high power handlingcapacity is proposed, which consists of coaxial feed structure and flare angle horn. Lowband microwave is fed by Coa.TE11mode, and high band microwave is fed by Cir.TE11mode. Based on the specific structure of the horn antenna, mode matching method isutilized to determine scatter matrix of each discontinuity in cross section. To obtain theoverall scatter matrix of the antenna, it is necessary to progressively cascade the scattermatrixs, and the overall scatter matrix determines the propagation properties of the hronantenna. Farfield radiation pattern of the dual-band antenna can easily get by usingmode expansion technology. Furthermore, a dual-band antenna at3.6GHz and9.5GHzis designed, and theoretical and numerical simulations agree well with each other. Itreveals that the dual-band antenna has high power handling capacity with several GWslevel, and good farfield radiation pattern at each band has been achieved.更多还原