Abstract Accessories in antennas can be seen as devices adapted to radiating or receiving electromagnetic wave structures. Their main purpose is to create means for the perfect operation of antennas. The accessories interconnect these antennas to the transmission and reception systems in an efficient and safe way. An electromagnetic coupling generally exists between the antennas and the accessories, and one can explore them to improve antenna performance. In this way, the accessories are as fundamental as the antenna proper, whose behavior is dependent on the appropriate connections. Several kinds of accessories, are used more frequently: attenuators, baluns, chokes, coaxial (coax) lines, insulators, lightning arresters, planar structures, phase shifters, and twin‐lead devices. These components will be described in the following sections.

Abstract This chapter gives an overview of the technology and design of radiofrequency (RF)‐integrated circuits in silicon technology. These circuits have transformed the field of wireless communications, forming the heart of sophisticated multiple‐input, multiple‐output RF transceivers for use in cellular handsets. The technology is now starting to transform new fields in the millimeter‐wave frequency range, enabling it to be used for new consumer applications such as radars for autonomous cars. The chapter describes the key active device technologies and passive components before going on to describe the state of the art in circuit design techniques. There are separate sections dedicated to the design of amplifiers, oscillators, mixers and modulators, and integrated transceivers. A final section gives an introduction to the importance of taking the packaging into account at the chip design and layout stage, as well as describing the rapidly emerging field of RF system‐in‐package technology, where sophisticated millimeter‐wave antenna arrays can be integrated with active circuits. The chapter includes 180 references to research papers describing advanced techniques developed in both industry and academia.

Abstract Microwave components, antennas, and systems that meet the tight requirements of today's advanced wireless terrestrial and satellite‐based communication systems—in particular concerning increased specifications and performance—demand fast EM‐based computer‐aided design (CAD) tools yielding accurate, highly optimized components within adequately short design times. This goal makes flexible and efficient hybrid solutions desirable, which typically go beyond the design capabilities of the involved single methods. The chapter presents an overview of the state of the art of hybrid CAD mode‐matching (MM)/finite‐element (FE)/method‐of‐moments (MoM) techniques applied for the rigorous, fast CAD and optimization of waveguide components, antennas and arrays and describes recent advances. The hybrid techniques presented combine advantageously the efficiency of the MM method with the flexibility of the FE method and the efficiency and flexibility of MoM for radiating structures. Typical application examples illustrate the versatility and high efficiency of these hybrid techniques.

Abstract Antenna measurements have a wide range of end uses; in many cases, the need is to verify as‐built performance against the evermore sophisticated design tools. These electromagnetic design tools now include details on surface roughness and dielectric loading with computational speeds that make these problem easily completed on engineering workstation that would have required supercomputers a decade ago. In addition, the resulting simulations can be tied from RF (radio frequency) fields into detailed physics associated with power handling due to heat, corona breakdown, saturation, and multipaction. Properly verifying the performance has hence become more complex as the margins continue to be reduced on as‐built designs, and the antennas have more embedded electronics. Antenna measurements have thus become more detailed with the increasing complexity of antennas. In the 1950s, the phase or quadrature response of the antenna was not required for many systems, only power detection was necessary. As the systems started to use techniques of phase and frequency modulation, the measurement of phase became more essential to characterizing system performance and improving polarization data also. Next, the need for knowledge extended to frequency and eventually time domain as increasingly the antenna became another electronic component in the microwave designers' tool kit. In the 2000s, the antenna has evolved into a shaped multibeam, polarization, and frequency agile device, not just for the military but for communications systems as well. In application, the next generation, from the 2020s onward, will see the concept of an antenna become blurred as the digital realm begins to reach down into the final layers of RF devices to the antenna itself. Not all antenna testing is providing measurements of fields, but for this article, the author will not investigate testing that is not unique to antennas, such as temperature, vibration, shock, humidity, stress, wind, and other possibilities. Unless the RF properties are part of the performance evaluated during these other types of tests, the testing methods would be the same as for any black box taken to an environmental test facility.

Abstract This article reviews and summarizes the research and development work conducted in the area of complex media, with emphasis on (1) model clarifications of anisotropic and bianisotropic media and (2) typical simulation methods. Many application examples are included to address issues in the complex media, where partial solutions are provided as well.

Abstract This article reviews considerations related to exposure assessment and biological effects of radiofrequency energy with emphasis on health and safety. The rationale for two major exposure limits is described. Major areas of controversy about health effects of low‐level radiofrequency energy are described, both as related to uncertainties in the scientific data and in large variations in exposure limits around the world.

Abstract This chapter reviews the basic principles of transient circuit analysis, which is a long‐established branch of circuit theory with a wide range of applications. It examines transient behavior in linear circuits and explains the type of behavior that can occur in these circuits. It shows how this behavior can be analyzed by solving appropriate differential equations or by applying the Laplace transform. A brief discussion of transient simulation for nonlinear radio frequency (RF) circuits is also provided, showing how arbitrary frequency‐defined models may be handled via a rational model and time‐domain convolution.

Abstract Explosion of the multitude of current and future wireless services has motivated the search for more efficient ways to allocate spectrum than fixed channel allocations enforced by regulatory agencies. In particular, dynamic spectrum‐sharing techniques allow spectrum to be assigned or selected for use based on the users and demand in a given geographic region. In this chapter, we consider collaborative spectrum sharing (CSS), in which users or networks share information about their spectrum needs and usage to facilitate efficient use of spectrum resources. We provide an ontology of CSS approaches and give an overview of previous CSS research. Then, we provide a more in‐depth discussion of the roles of CSS in two different example systems. The first is the Citizen Broadband Radio Service (CBRS), which is a system established by the Federal Communications Commission (FCC) in the United States, and which uses a centralized, hierarchical approach to CSS. The second is the Spectrum Collaboration Challenge (SC2), which was a competition run by the Defense Advanced Research Projects Agency (DARPA) in the United States to develop intelligent radios systems for CSS. In contrast to CBRS, the SC2 enforces a distributed, unified approach to CSS. The chapter concludes with a brief discussion of the progress and challenges in implementing CSS.

Abstract High‐power microwave (HPM) sources are at the heart of an HPM‐directed energy weapons (DEWs) system. Based on recent defense news articles seen in online magazines such as The Warzone , it is becoming more and more apparent that in the future the survival of a nation may depend on its DEW capability. This chapter provides a brief synopsis of a wide range of microwave tubes which are used for the generation of HPM signals. The chapter starts with a brief introduction on DEWs and their applications followed by a discussion on the basic building blocks of an HPM system. The sections that follow contain generalized physics of operation, frequency range, and output power capability of the following HPM tubes: magnetrons, backward wave oscillators (BWOs), klystrons, traveling wave tubes (TWTs), gyrotrons, virtual cathode oscillators (VCOs), magnetically insulated line oscillators (MILOs), transit time oscillators (TTOs), split cavity oscillators (SCOs), and reltrons. Of all the microwave tubes, the magnetron has been discussed in a little more detail because of its rich history. References have been provided for readers who wish to gain further knowledge in each area.

Abstract Electromagnetic modeling is a critical analysis and design methodology in various fields such as radio‐frequency (RF) and microwave engineering, antennas, radar, remote sensing, medical diagnostics, bio‐electromagnetics, physics and radio astronomy, and electromagnetic compatibility (EMC) and interference. It formulates and solves electromagnetic field problems using mathematical, physical, or computational models that relate the electromagnetic functionality of devices to their geometrical and material parameters or predict how electromagnetic fields interact with physical objects and materials. This chapter presents the most common methods for modeling electromagnetic scenarios in the frequency, the spectral, and the time domain, as well as their hybrid combinations. They are introduced as projective approximations of field solutions using the method of weighted residuals (MWR). This unified perspective best illustrates their properties, differences, and their suitability for solving a particular electromagnetic problem, thus helping the reader to appreciate the connections, similarities, and differences among the various methods. It also reflects historical and methodological developments and aims to provide a foundational understanding of current electromagnetic modeling methods.