外文原文：
Preface
The continuing popularity of Microwave Engineering is gratifying. I have received many letters and emails from students and teachers from around the world with positive comments and suggestions. I think one reason for its success is the emphasis on the fundamentals of electromagnetics, wave propagation, network analysis, and design principles as applied to modern RF and microwave engineering. As I have stated in earlier editions, I have tried to avoid the handbook approach in which a large amount of information is presented with little or no explanation or context, but a considerable amount of material in this book is related to the design of specific microwave circuits and components, for both practical and motivational value. I have tried to base the analysis and logic behind these designs on first principles, so the reader can see and understand the process of applying fundamental concepts to arrive at useful results. The engineer who has a firm grasp of the basic concepts and principles of microwave engineering and knows how these can be applied toward practical problems is the engineer who is the most likely to be rewarded with a creative and productive career.
For this new edition I again solicited detailed feedback from teachers and readers for their thoughts about how the book should be revised. The most common requests were for more material on active circuits, noise, nonlinear effects, and wireless systems. This edition, therefore, now has separate chapters on noise and nonlinear distortion, and active devices. In Chapter 10, the coverage of noise has been expanded, along with more material on intermodulation distortion and related nonlinear effects. For Chapter 11, on active devices, I have added updated material on bipolar junction and field effect transistors, including data for a number of commercial devices (Schottky and PIN diodes, and Si, GaAs, GaN, and SiGe transistors), and these sections have been reorganized and rewritten. Chapters 12 and 13 treat active circuit design, and discussions of differential amplifiers, inductive degeneration for nMOS amplifiers, and differential FET and Gilbert cell mixers have been added. In Chapter 14, on RF and microwave systems, I have updated and added new material on wireless communications systems, including link budget, link margin, digital modulation methods, and bit error rates. The section on radiation hazards has been updated and rewritten. Other new material includes a section on transients on transmission lines (material that was originally in the first edition, cut from later editions, and now brought back by popular demand), the theory of power waves, a discussion of higher order modes and frequency effects for microstrip line, and a discussion of how to determine unloaded Q from resonator measurements. This edition also has numerous new or revised problems and examples, including several questions of the “open-ended” variety. Material that has been cut from this edition includes the quasi-static numerical analysis of microstrip line and some material related to microwave tubes. Finally, working from the original source files, I have made hundreds of corrections and rewrites of the original text.
Today, microwave and RF technology is more pervasive than ever. This is especially true in the commercial sector, where modern applications include cellular telephones, smartphones, 3G and WiFi wireless networking, millimeter wave collision sensors for vehicles, direct broadcast satellites for radio, television, and networking, global positioning systems, radio frequency identification tagging, ultra wideband radio and radar systems, and microwave remote sensing systems for the environment. Defense systems continue to rely heavily on microwave technology for passive and active sensing, communications, and weapons control systems. There should be no shortage of challenging problems in RF and microwave engineering in the foreseeable future, and there will be a clear need for engineers having both an understanding of the fundamentals of microwave engineering and the creativity to apply this knowledge to problems of practical interest.
Modern RF and microwave engineering predominantly involves distributed circuit analysis and design, in contrast to the waveguide and field theory orientation of earlier generations. The majority of microwave engineers today design planar components and integrated circuits without direct recourse to electromagnetic analysis. Microwave computeraided design (CAD) software and network analyzers are the essential tools of today’s microwave engineer, and microwave engineering education must respond to this shift in emphasis to network analysis, planar circuits and components, and active circuit design. Microwave engineering will always involve electromagnetics (many of the more sophisticated microwave CAD packages implement rigorous field theory solutions), and students will still benefit from an exposure to subjects such as waveguide modes and coupling through apertures, but the change in emphasis to microwave circuit analysis and design is clear.
This text is written for a two-semester course in RF and microwave engineering for seniors or first-year graduate students. It is possible to use Microwave Engineering with or without an electromagnetics emphasis. Many instructors today prefer to focus on circuit analysis and design, and there is more than enough material in Chapters 2, 4–8, and 10–14 for such a program with minimal or no field theory requirement. Some instructors may wish to begin their course with Chapter 14 on systems in order to provide some motivational context for the study of microwave circuit theory and components. This can be done, but some basic material on noise from Chapter 10 may be required.
Two important items that should be included in a successful course on microwave engineering are the use of CAD simulation software and a microwave laboratory experience. Providing students with access to CAD software allows them to verify results of the design-oriented problems in the text, giving immediate feedback that builds confidence and makes the effort more rewarding. Because the drudgery of repetitive calculation is eliminated, students can easily try alternative approaches and explore problems in more detail. The effect of line losses, for example, is explored in several examples and problems; this would be effectively impossible without the use of modern CAD tools. In addition, classroom exposure to CAD tools provides useful experience upon graduation. Most of the commercially available microwave CAD tools are very expensive, but several manufacturers provide academic discounts or free “student versions” of their products. Feedback from reviewers was almost unanimous, however, that the text should not emphasize a particular software product in the text or in supplementary materials.
A hands-on microwave instructional laboratory is expensive to equip but provides the best way for students to develop an intuition and physical feeling for microwave phenomena. A laboratory with the first semester of the course might cover the measurement of microwave power, frequency, standing wave ratio, impedance, and scattering parameters, as well as the characterization of basic microwave components such as tuners, couplers, resonators, loads, circulators, and filters. Important practical knowledge about connectors, waveguides, and microwave test equipment will be acquired in this way. A more advanced laboratory session can consider topics such as noise figure, intermodulation distortion, and mixing. Naturally, the type of experiments that can be offered is heavily dependent on the test equipment that is available.
Additional resources for students and instructors are available on the Wiley website. These include PowerPoint slides, a suggested laboratory manual, and an online solution manual for all problems in the text (available to qualified instructors, who may apply for access at the website http://he-cda.wiley.com/wileycda/).
外文翻译：
前言
微波工程的继续流行是令人欣喜的。我收到了来自世界各地的学生和教师的许多信件和电子邮件，积极的评论和建议。我认为其成功的一个原因是强调电磁学，波传播，网络分析和应用于现代RF和微波工程的设计原理的基本原理。正如我在早期版本中所述，我试图避免手册方法，其中提供大量的信息，很少或没有解释或上下文，但本书中相当多的材料与特定微波的设计有关电路和组件，用于实际和动机价值。我试图将这些设计背后的分析和逻辑放在第一个原则上，以便读者可以看到并理解应用基本概念以获得有用结果的过程。熟练掌握微波工程的基本概念和原理，知道如何应用这些技术应用于实际问题的工程师是最有可能获得创造性和生产性职业奖励的工程师。对于这个新版本，我再次征求教师和读者对他们关于如何修订这本书的想法的详细反馈。最常见的要求是有源电路，噪声，非线性效应和无线系统的更多材料。
因此，本版本现在有关于噪声和非线性失真的单独章节，以及有源器件。在第10章中，噪声的覆盖范围已扩大，以及更多关于互调失真和相关非线性效应的材料。对于第11章，在有源器件上，我添加了双极结和场效应晶体管的更新材料，包括许多商业器件（肖特基和PIN二极管，Si，GaAs，GaN和SiGe晶体管）的数据，这些部分已经重组和重写。第12章和第13章讨论了有源电路设计，并且增加了差分放大器，nMOS放大器的电感退化以及差分FET和吉尔伯特单元混频器的讨论。在第14章，关于射频和微波系统，我已经更新和添加了无线通信系统的新材料，包括链路预算，链路余量，数字调制方法和误码率。关于辐射危害的部分已经更新和重写。其他新材料包括传输线上的瞬变部分（原始在第一版中的材料，从以后的版本中切割出来，现在由普遍需求带回），功率波理论，高阶模和频率效应的讨论用于微带线，以及如何从谐振器测量确定无载Q的讨论。此版本还有许多新的或修订的问题和例子，包括几个问题的“开放式”品种。从这一版本剪切的材料包括微带线的准静态数值分析和一些与微波管有关的材料。最后，从原始源文件，我做了数百的更正和重写的原始文本。
今天，微波和射频技术比以往任何时候都更加普遍。这在商业部门尤其如此，其中现代应用包括蜂窝电话，智能电话，3G和WiFi无线网络，用于车辆的毫米波碰撞传感器，用于无线电，电视和网络的直接广播卫星，全球定位系统，射频识别标记，超宽带无线电和雷达系统，以及用于环境的微波遥感系统。国防系统继续严重依赖微波技术用于被动和主动传感，通信和武器控制系统。
在可预见的未来，在RF和微波工程中应该不缺乏具有挑战性的问题，并且将清楚地需要具有对微波工程的基本原理的理解的工程师和将该知识应用于实际感兴趣的问题的创造性。现代RF和微波工程主要涉及分布式电路分析和设计，与前几代的波导和场理论取向相反。大多数微波工程师现在设计平面元件和集成电路，而不直接求助于电磁分析。微波计算机网络设计（CAD）软件和网络分析仪是当今微波工程师的必备工具，微波工程教育必须对网络分析，平面电路和元件以及有源电路设计的重点作出反应。微波工程总是涉及电磁学（许多更复杂的微波CAD软件包实现严格的场理论解决方案），学生仍然可以从暴露于诸如波导模式和耦合通孔的主题，但是重点改变到微波电路分析设计清晰。
本文是针对老年人或第一年研究生的RF和微波工程两学期课程编写的。可以使用具有或不具有电磁体强调的微波工程。许多教师今天更喜欢专注于电路分析和设计，在第2，4-8和10-14章有足够的材料，这样的程序具有最小或没有现场理论要求。一些教师可能希望开始他们的课程与第14章系统，以便为微波电路理论和组件的研究提供一些动机的背景。这可以做到，但是可能需要一些关于第10章噪音的基本材料。
一个成功的微波工程课程应该包括两个重要的项目是使用CAD模拟软件和微波实验室经验。为学生提供CAD软件的访问权限，使他们能够验证文本中面向设计的问题的结果，立即提供反馈，建立信任并使工作更有成效。因为重复计算的苦差消除了，学生可以很容易地尝试替代方法和更详细地探讨问题。例如，在几个例子和问题中探讨了线路损耗的影响;如果不使用现代CAD工具，这将是不可能的。此外，课堂暴露于CAD工具在毕业时提供有用的经验。大多数市售微波CAD工具非常昂贵，但是几个制造商提供学术折扣或其产品的免费“学生版本”。然而，评论者的反馈几乎是一致的，文本不应强调文本或补充材料中的特定软件产品。一个实际操作的微波教学实验室装备昂贵，但为学生提供了微波现象的直觉和物理感觉的最佳方式。具有课程第一学期的实验室可以涵盖微波功率，频率，驻波比，阻抗和散射参数的测量，以及诸如调谐器，耦合器，谐振器，负载，循环器等基本微波部件的表征。和过滤器。以这种方式将获得关于连接器，波导和微波测试设备的重要的实践知识。更高级的实验室课程可以考虑诸如噪声系数，互调失真和混合等主题。自然地，可以提供的实验类型严重依赖于可用的测试设备。
