Compact-Size Wideband Antennas and Arrays for Wireless Communications

Polarization is an important parameter for characterizing antenna systems. Dual-polarized and circularly-polarized wideband antennas with compact size are very useful for mobile communications and satellite communications. Due to the multipath propagation and shadowing in urban environment, radio signals received by mobile terminals can become very weak. Dual-polarized antennas can achieve better signal quality in mobile communications by using polarization diversity. Wideband circularly polarized antennas are very important for mobile satellite communications as circularly polarized signals are immune to Faraday rotation effects. Circular polarization also enables mobile satellite communications without strict alignment between transmit and receive antennas. Therefore, dual-polarized antennas and circularly polarized antennas have been drawn increasing popularity in the wireless communication systems. In this thesis, several novel designs of compact, wideband, and specially functioned antennas and arrays are developed for wireless communication applications. First, wideband antennas and arrays are investigated for base station applications with different appealing features, such as compact radiator size, enhanced upper out-of-band suppression, or low pattern sidelobes. They are designed with different novel design concept, such as shared-dipole, electromagnetic dipoles, shorted dipoles, and fourth-order coupling structure. Then, to directly match to the newly emerged differential circuit systems, several wideband differentially fed dual-polarized antennas are proposed for base station applications. They are designed for high common mode suppression, high harmonic suppression, or compact radiator size by using the idea of orthogonal six-port power divider, multi-resonance structure, and crossed open loop resonators. The final designs are two circularly polarized antennas, which have the wide overlapped impedance and axial ratio bandwidth, or dual circularly polarized radiations realized by using crossed open slot-pairs, orthogonal power diver, and phase shift unit cells. The working principles of these different antennas are extensively illustrated with the relevant design theories and detailed structure studies. The performances of these antennas and arrays are evaluated first by the full-wave electromagnetics simulations, and followed by the measurements of the corresponding fabricated prototypes. Good agreements between the simulated and measured results are obtained. With these different features to accommodate different requirements, these antennas and arrays can be the good candidates for the wireless communication systems

Antenna Designs for 5G/IoT and Space Applications

This book is intended to shed some light on recent advances in antenna design for these new emerging applications and identify further research areas in this exciting field of communications technologies. Considering the specificity of the operational environment, e.g., huge distance, moving support (satellite), huge temperature drift, small dimension with respect to the distance, etc, antennas, are the fundamental device allowing to maintain a constant interoperability between ground station and satellite, or different satellites. High gain, stable (in temperature, and time) performances, long lifecycle are some of the requirements that necessitates special attention with respect to standard designs. The chapters of this book discuss various aspects of the above-mentioned list presenting the view of the authors. Some of the contributors are working strictly in the field (space), so they have a very targeted view on the subjects, while others with a more academic background, proposes futuristic solutions. We hope that interested reader, will find a fertile source of information, that combined with their interest/background will allow efficiently exploiting the combination of these two perspectives

Antenna Design for 5G and Beyond

With the rapid evolution of the wireless communications, fifth-generation (5G) communication has received much attention from both academia and industry, with many reported efforts and research outputs and significant improvements in different aspects, such as data rate speed and resolution, mobility, latency, etc. In some countries, the commercialization of 5G communication has already started as well as initial research of beyond technologies such as 6G.MIMO technology with multiple antennas is a promising technology to obtain the requirements of 5G/6G communications. It can significantly enhance the system capacity and resist multipath fading, and has become a hot spot in the field of wireless communications. This technology is a key component and probably the most established to truly reach the promised transfer data rates of future communication systems. In MIMO systems, multiple antennas are deployed at both the transmitter and receiver sides. The greater number of antennas can make the system more resistant to intentional jamming and interference. Massive MIMO with an especially high number of antennas can reduce energy consumption by targeting signals to individual users utilizing beamforming.Apart from sub-6 GHz frequency bands, 5G/6G devices are also expected to cover millimeter-wave (mmWave) and terahertz (THz) spectra. However, moving to higher bands will bring new challenges and will certainly require careful consideration of the antenna design for smart devices. Compact antennas arranged as conformal, planar, and linear arrays can be employed at different portions of base stations and user equipment to form phased arrays with high gain and directional radiation beams. The objective of this Special Issue is to cover all aspects of antenna designs used in existing or future wireless communication systems. The aim is to highlight recent advances, current trends, and possible future developments of 5G/6G antennas

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

Artificial Magnetic Conductor Integrated Textile Monopole Antenna

Wearable antenna is a fast growing field in application-oriented research, which introduced a new generation of garments capable of monitoring wear health, as well as environmental states. This thesis is concerned with the design and fabrication of a compact textile wearable antenna at operating frequency within the Industrial, Scientific and Medical (ISM) band, intended for integration into a flight jacket of the astronaut inside the habitat. The antenna is integrated with artificial material known as High Impedance Surface (HIS) for performance enhancement. The purpose of the system is to constantly monitor vital signals of the astronauts. The entire design cycle of wearable Co-Planar Waveguide (CPW) fed monopole antenna, starting from simulation-based design to fabricated prototype and antenna testing under different conditions was carried out in this thesis. Because of the lossy nature of human body tissues, the radiation efficiency of the antenna will be reduced due to the absorption of the radiated energy. Hence, changes in the radiation characteristics of the wearable antenna like operating frequency, gain and impedance bandwidth will take place. To overcome these challenges, HIS has been suggested and integrated with the monopole antenna to isolate the antenna from the ambient environments. This wearable antenna was tested under real operating conditions such as bending and crumpling conditions. Moreover, as the antenna operates near human body tissues, Specific Absorption Rate (SAR) assessment is required to consider the safety concerns of the antenna system. SAR analysis based on simulation results has been carried out in this thesis to show a significant reduction in SAR with the usage of HIS in the antenna system

Impedance Transformers

Non

Novel High Isolation Antennas for Simultaneous Transmit and Receive (STAR) Applications

Radio frequency (RF) spectrum congestion is a major challenge for the growing need of wireless bandwidth. Notably, in 2015, the Federal Communications Commission (FCC) auctioned just 65 MHz (a bandwidth smaller than that used for WiFi) for more than $40 billion, indicating the high value of the microwave spectrum. Current radios use one-half of their bandwidth resource for transmission, and the other half for reception. Therefore, by enabling radios to transmit and receive across their entire bandwidth allocation, spectral efficiency is doubled. Concurrently, data rates for wireless links also double. This technology leads to a new class of radios and RF frontends. Current full-duplex techniques resort to either time- or frequency-division duplexing (TDD and FDD respectively) to partition the transmit and receive functions across time and frequency, respectively, to avoid self-interference. But these approaches do not translate to spectral efficiency. Simultaneous transmit and receive (STAR) radios must isolate the transmitter from the receiver to avoid self-interference (SI). This SI prevents reception and must therefore be cancelled. Self-interference may be cancelled with one or more stages involving the antenna, RF or analog circuits, or digital filters. With this in mind, the antenna stage is the most critical to reduce the SI level and avoid circuit saturation and total system failure. This dissertation presents techniques for achieving STAR radios. The initial sections of the dissertation provide the general approach of stage to stage cancellation to achieve as much as 100 dB isolation between the receiver and transmitter. The subsequent chapters focus on different antennas to achieve strong transmit/receive isolation. As much as 35 dB isolation is shown using a new spiral antenna array with operation across a 2:1 bandwidth. Also, a new antenna feed is presented showing 42 dB isolation across a 250 MHz bandwidth. Reflections in the presence of a dynamic environment are also considered

Some studies on designs of planar antennas for UWB applications

In Ultra-Wideband (UWB) wireless system, considerable research efforts have been put into the design of UWB antennas and communication systems. These UWB antennas are essential for providing wireless wideband communications based on the use of very narrow pulses on the order of nanoseconds, covering a very wide bandwidth in the frequency domain and over very short distance at very low power densities. Also it is well known that, in traditional narrow-band communications, multiple antenna systems offer attractive aspects in wireless communication by means of Multiple-Input Multiple-Output (MIMO) techniques. These techniques either give out high channel capacities through spatial multiplexing, or offer an increase of link robustness. The present work deals with four new compact broadband antennas, suitable for portable applications are designed and characterized, namely-octagon shaped monopole, semicircular disk monopole, semi-octagon shaped diversity, semi-circular diversity. The performances of these designs have been studied using standard simulation tools used in industry or academy and experimentally verified. One of the major contributions of the thesis lies in the analysis of the frequency and time-domain response of the designed UWB antennas to confirm their suitability for portable pulsed-UWB system. A technique to avoid narrow band interference by etching narrow slot resonators on the antenna is also proposed and their effects on a nano-second pulse have been investigated

Reconfigurable Antennas

In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed

Antenna Design for 5G and Beyond

This book is a reprint of the Special Issue Antenna Design for 5G and Beyond that was published in Sensors