Developments in Antenna Analysis and Design presents recent developments in antenna design and modeling techniques for a wide variety of applications, chosen because they are contemporary in nature, have been receiving considerable attention in recent years, and are crucial for future developments. It includes topics such as body-worn antennas, that play an important role as sensors for Internet of Things (IoT), and millimeter wave antennas that are vitally important for 5G devices. It also covers a wide frequency range that includes terahertz and optical frequencies. Additionally, it discusses topics such as theoretical bounds of antennas and aspects of statistical analysis that are not readily found in the existing literature. This first volume covers the theory of characteristic modes (TCM) and characteristic bases; wideband antenna element designs; MIMO antennas; antennas for wireless communication; reconfigurable antennas employing microfluidics; flexible and body-worn antennas; and antennas using meta-atoms and artificially-engineered materials, or metamaterials (MTMs). A second volume covers the topics of: graphene-based antennas; millimeter-wave antennas; terahertz antennas; optical antennas; fundamental bounds of antennas; fast and numerically efficient techniques for analyzing antennas; statistical analysis of antennas; ultra-wideband arrays; reflectarrays; and antennas for small satellites, viz., CubeSats. The two volumes represent a unique combination of topics pertaining to antenna design and analysis, not found elsewhere. It is essential reading for the antenna community including designers, students, researchers, faculty engaged in teaching and research of antennas, and the users as well as decision makers.
Inspec keywords: broadband antennas; MIMO communication; metamaterial antennas; leaky wave antennas; mobile antennas; microstrip antennas; loop antennas; directive antennas; microwave antennas; wearable antennas
Other keywords: artificially engineered materials; complex platforms; reconfigurable leaky-wave antennas; wearable antennas; wireless communications; antenna design; MIMO antenna systems; meta-atoms engineered materials; metamaterials antennas; reconfigurable high-gain antennas; Wearable technology; human health monitoring; characteristic basis function methods; mobile platform; flexible antennas; metasurfaces antennas; characteristic mode; wideband L-probe patch antenna; microwave antennas; microfluidically reconfigurable antennas; metamaterial-based zero-phase-shift-line loop antennas; antenna analysis
Subjects: Radio links and equipment; Single antennas
In this article discusses the characteristic mode analysis was done to identify and select two eigen-modes of the antenna that are significant (MS > 0.707) and to obtain information on the phase difference of these modes. With this knowledge, antennas with circularly polarized patterns can be designed by combining the two orthogonal characteristic modes with a 90° phase difference. In the wideband antenna case, the MSs of the antenna's characteristic modes were examined to find modes that are significant over a wide bandwidth. Subsequently, the eigen-currents and the eigen-fields of the wideband modes were evaluated to find modes that possess omni-directional radiation patterns, which is an essential property of ultrawideband antennas. In the example of chassis antenna design, two significant chassis modes were excited using the same set of capacitive coupling elements. This was accomplished by understanding the MSs and the eigen-current distributions of the two desired modes, and by placing the capacitive coupling elements at the locations where the magnitudes of the eigen-currents are the weakest for these modes. Loop antennas were mainly used as inductive coupling elements to excite a desired mode of a metallic platform, and a systematic approach to enhance the bandwidth of the platform-based antenna was demonstrated. This approach employed the characteristic mode theory to examine the MSs and the eigen-current distributions of the platform modes, and to calculate the maximum available bandwidth that the desired characteristic mode could offer. The characteristic mode theory can be used as a tool to aid antenna design by allowing engineers to interpret the physical characteristics of the radiator(s).
In this chapter, we will discuss two types of antenna design strategies, tailored for two different categories of antenna design problems. First of these will address the well-known problem of designing a multiband antenna, to be mounted on a mobile phone platform, to simultaneously cover the typical communication bands, for example, LTE, GSM, Bluetooth, WiMax, etc., with only a single antenna tailored for the platform, as is usually the requirement, except for MIMO applications. Next, we will turn to the problem of designing a plurality of antennas to be located on a complex platform to achieve certain radiation characteristics deemed desirable by the user, in order to receive the desired signals while suppressing the interfering ones. While several methods for radiation pattern synthesis of antennas exist in literature, They are only applicable to specific antenna geometries and they typically do not handle complex structures. The pattern synthesis problem is of great interest in many practical applications, for example, global positioning system (GPS) antenna design, and locating multiple antennas mounted on the rooftop of a large vehicle, or on the topside of a ship.
The two related feeding techniques, namely, the L-shaped probe and meandering probe (M-probe), for broadening the bandwidth of patch antenna are reviewed. The L-probe has a simple structure and wide bandwidth whereas the M-probe has low cross polarization and a symmetric radiation pattern within the operating frequencies. Design guidelines of the two kinds of patch antennas for Wi-Fi applications are presented. All the impedance bandwidths of the antennas were optimized to standing wave ratio (SWR) less than 1.5. The performance of the patch antennas with different patch height and aspect ratio is demonstrated. The performance of a wide M-probe fed patch antenna that has an impedance bandwidth of around 44% is presented. Finally, a review of various designs for different applications is discussed.
Multiple-input-multiple-output (MIMO) technology is currently used in fourthgeneration (4G) wireless systems because they can provide higher data rates at fixed power and bandwidth levels when compared to their single-input-singleoutput conventional counterparts. MIMO-enabled systems require the integration of multiple antenna elements operating at the same band to provide higher data throughput. The design of such antenna solutions is a challenging task especially for small form factor devices where the space is limited and the antennas are placed close to one another. Such close placement of antennas with respect to one another will increase the port coupling between adjacent antennas as well as radiated field coupling, thus degrading the efficiency as well as increasing field correlation. This will affect the overall improvement in the data rates (channel capacity) expected. In this chapter, we will go over the latest advancements in MIMO antenna system designs for 4G and the anticipated 5G wireless standard and will highlight various challenges that can be encountered and provide the solutions to overcome them.
In this chapter, an overview of the recent development of reconfigurable high-gain antennas is presented. These antennas range from reconfigurable Yagi antennas, reconfigurable reflectarrays and reconfigurable transmitarrays to reconfigurable PRS antennas. It is demonstrated that PRS antennas are able to reconfigure their frequency, polarization and radiation patterns with high realized gains. Compared with RA arrays, reconfigurable reflectarrays and transmitarrays, it is much easier for reconfigurable PRS antennas to achieve various reconfigurations with a simpler biasing network. In order to fully exploit the diversities of antennas in wireless communication and radar systems, compound reconfigurations of two or three antenna parameters are highly desired. However, there have been no reported products employing such combined RAs. Since PRS antennas have more freedom of parameters (a single feeding source/feeding source arrays and a PRS structure), the above challenge could be addressed by allocating different reconfigurations to different parts. As this work progresses, there is no doubt that fully reconfigurable PRS antennas will deliver significant benefits to practical wireless systems in future.
In this chapter, an overview of the recent development of reconfigurable high-gain antennas is presented. These antennas range from reconfigurable Yagi antennas, reconfigurable reflectarrays and reconfigurable transmitarrays to reconfigurable PRS antennas. It is demonstrated that PRS antennas are able to reconfigure their frequency, polarization and radiation patterns with high realized gains. Compared with RA arrays, reconfigurable reflectarrays and transmitarrays, it is much easier for reconfigurable PRS antennas to achieve various reconfigurations with a simpler biasing network. In order to fully exploit the diversities of antennas in wireless communication and radar systems, compound reconfigurations of two or three antenna parameters are highly desired. However, there have been no reported products employing such combined RAs. Since PRS antennas have more freedom of parameters (a single feeding source/feeding source arrays and a PRS structure), the above challenge could be addressed by allocating different reconfigurations to different parts. As this work progresses, there is no doubt that fully reconfigurable PRS antennas will deliver significant benefits to practical wireless systems in future.
In this chapter is to present an overview of the microfluidically reconfigurable antennas by discussing antenna examples from the recent literature. The subsequent section briefly summarizes the fabrication and actuation techniques employed by several research groups. As a representative example, fabrication steps followed in for construction of a microfluidics-based mm-wave beam-steering antenna array. The remaining sections group the discussion on the microfluidically reconfigurable antennas under “flexible and stretchable liquid metal antennas”, “frequency-reconfigurable liquid metal antennas”, “reconfigurable antennas using dielectric liquids”, “beam-steerable liquid metal antennas”, and “reconfigurable antennas using microfluidically repositionable metallized plates”.
in this chapter discusses the planar-inverted F-antenna (PIFA) is used for the wearable application, which reduces the effect of radiation on the human body by reducing the radiated power towards the body. As the Global System for Mobile Communication (GSM) transmitted power is reduced, the battery life is increased. This performance is achieved due to matching the feed with the load that reduces the power loss because of reduction in the reflected power. A FlexPIFA antenna is designed from the flexible dielectric material for the smart clothing application. The transmission range was calculated based on Friis expression. Another PIFA antenna that is integrated with the human body for a mobile phone.
Health and long-term care is a growth area for wearable heath monitoring systems. Wearable diagnostic and therapeutic systems can contribute to timely point-of-care (POC) for patients with chronic health conditions, especially chronic neurological disorders, cardiovascular diseases and strokes that are leading causes of mortality worldwide. Diagnostics and therapeutics for patients under timely POC can save thousands of lives. However, lack of access to minimally intrusive monitoring systems makes timely diagnosis difficult and sometimes impossible. Existing ambulatory recording equipment is incapable of performing continuous remote patient monitoring (RPM) because of the inability for conventional silver-silver-chloride-gel-electrodes to perform long-term monitoring, non-reusability, lack of scalable-standardized wireless communication platforms, and user-friendly design. Recent progress in nanotextile biosensors and mobile platforms has resulted in novel wearable health monitoring systems for neurological and cardiovascular disorders. This chapter discusses nanostructured-textile-based dry electrodes that are better suited for long-term measurement of electrocardiography (ECG), electroencephalography (EEG), electrooculography (EOG), electromyography (EMG), and bioimpedance with very low baseline noise, improved sensitivity, and seamless integration into garments of daily use. It discusses bioelectromagnetic principles of origination and propagation of bioelectric signals and nanosensor functioning, which provide a unique perspective on the development of novel wearable systems that harness their potential. Combined with state-of-the-art embedded wireless network devices and printable fractal antenna to communicate with smartphone, laptop, or directly to remote server through mobile network (GSM, 4G-LTE, GPRS), they can function as wearable wireless health diagnostic systems that are more intuitive to use.
In this article chapter, we discuss different ways to mitigate some of the problems encountered with MTMs, and present strategies for artificially synthesizing dielectric materials that are broadband as well as low-loss; hence, they are useful for real-world antenna applications involving low-profile flat lenses and reflectarrays, for example. The key to circumventing the difficulties with MTM, which we have identified above, is to steer clear of the common practice of using resonant inclusions or “particles”to achieve extreme material properties, negative index; and, zero index. Our strategy is to develop antenna designs that only call for material parameters that are realistic, so that they can either be acquired off-the-shelf, or by slightly tweaking the available materials by embedding small patches or apertures, often referred to as “particles”, whose dimensions are far removed from the resonance range. This obviates the problems of dispersion, narrow bandwidths and losses that plague the MTMs, at least those that fall in the “exotic”category, for example, the doublenegative or DNG type. Although the RO approach leads to dielectric-only designs that do not need to use magnetic materials, these designs still typically require dielectric materials that may not be available off-the-shelf.
In this chapter, we focus on introducing the microwave MTM antennas and their practical applications. We demonstrate the design, realization, and measurement of several types of MTM antennas. Generally, they are categorized into two groups: the flat or curved gradient-refractive-index (GRIN) lens antennas composed of isotropic or anisotropic MTMs, and the transformation optics (TO)-based lens antennas which have distinct performances and novel functions compared with traditional antennas. In the end of the chapter, we also give a brief introduction of metasurfaces, the two-dimensional (2D) version of MTMs, and introduce some important and latest applications of metasurfaces for antenna engineering.
The metamaterial-based zero-phase-shift-line (ZPSL) structures have exhibited unique dispersion characteristic which enables the flowing current along it featuring very small phase lag. This chapter has outlined the ZSPL configurations, the dispersion characteristic analysis approaches based on electromagnetic simulation and circuit model, and the design guidelines. A number of ZPSL loop antenna designs have been exemplified for different applications. The relevant discussions are believed to benefit the antenna researchers, engineers, and students to further understand of the ZPSL structure and development new ZPSL-based antennas.