Review on the Design of the Isolation Techniques for UWB-MIMO Antennas

Ultra wide band - Multiple Input Multiple Output antenna technology provides higher data rates and the combination of the ultra wide band (UWB) and the multiple input multiple output (MIMO) technologies provides a solution for the demand of still higher data rates i.e. in excess of 3 Gb/sec in the future.  As the antenna technologies are improving, the size of the MIMO antenna is growing smaller and smaller. Placing the antenna elements in such close proximity increases the coupling between them. Various isolation techniques have to be introduced between the antenna elements to decrease the coupling and to improve the isolation. A study of the various isolation enhancement techniques have been made in this review. It analyses the various isolation enhancement methods such as using orthogonal polarization, parasitic elements, varied decoupling structures, defected ground structures (DGS), neutralization line (NL) and finally by using metamaterials. Metamaterials is a technology to perk up the isolation between the antenna elements. Split ring resonator (SRR) behaves as a metamaterial and it is used as an isolation mechanism in this study. The antennas are simulated and the results are compared. The method using parasitic elements gives the highest isolation of 35 dB and it is 5 dB better than the methods using orthogonal polarization and using the decoupling structure. The performance of all the antennas satisfies the conditions for minimum isolation. The envelope correlation coefficient is nearly zero in all the antennas and it implies good diversity performance. The diversity gain is also calculated for the various antennas and it satisfies good diversity performance. The bandwidth of the antennas is in the UWB frequency range and they have a fractional bandwidth above the required value of 1.09. The capacity loss for all the antennas is very low and the antennas using defected ground structure and the decoupling structure gives very low capacity loss

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

UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications

Orbital angular momentum (OAM) has aroused a widespread interest in many fields, especially in telecommunications due to its potential for unleashing new capacity in the severely congested spectrum of commercial communication systems. Beams carrying OAM have a helical phase front and a field strength with a singularity along the axial center, which can be used for information transmission, imaging and particle manipulation. The number of orthogonal OAM modes in a single beam is theoretically infinite and each mode is an element of a complete orthogonal basis that can be employed for multiplexing different signals, thus greatly improving the spectrum efficiency. In this paper, we comprehensively summarize and compare the methods for generation and detection of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications and technical challenges of OAM in communications, including free-space optical communications, optical fiber communications, radio communications and acoustic communications. To complete our survey, we also discuss the state of art of particle manipulation and target imaging with OAM beams

Low-profile and closely spaced four-element mimo antenna for wireless body area networks

A compact four-element multiple-input multiple output (MIMO) antenna is proposed for medical applications operating at a 2.4 GHz ISM band. The proposed MIMO design occupies an overall volume of 26 mm × 26 mm × 0.8 mm. This antenna exhibits a good impedance matching at the operating frequency of the ISM band, whose performance attributes include: isolation around 25 dB, envelope correlation coefficient (ECC) less than 0.02, average channel capacity loss (CCL) less than 0.3 bits/s/Hz and diversity gain (DG) of around 10 dB. The average peak realized gain of the four-element MIMO antenna is 2.4 dBi with more than 77 % radiation efficiency at the frequency of interest (ISM 2.4 GHz). The compact volume and adequate bandwidth, as well as the good achieved gain, make this antenna a strong candidate for bio-medical wearable applications

Geometry Modification Assessment and Design Optimization of Miniaturized Wideband Antennas

Maintaining small physical dimensions of antenna structures is an important consideration for contemporary wireless communication systems. Typically, antenna miniaturization is achieved through various topological modifications of the basic antenna geometries. The modifications can be applied to the ground plane, the feed line, and/or antenna radiator. Unfortunately, various topology alteration options are normally reported on a case-to-case basis. The literature is lacking systematic investigations or comparisons of different modification methods and their effects on antenna miniaturization rate as well as electrical performance. Another critical issue—apart from setting up the antenna topology—is a proper adjustment of geometry parameters of the structure so that the optimum design can be identified. Majority of researchers utilize experience-driven parameter sweeping which typically yields designs that are acceptable, but definitely not optimal. Furthermore, in many of the cases, the authors provide a cooperative progression before and after topological modifications that generally lead to a certain reduction of the antenna size, however, with appropriate parameter adjustment missing. Consequently, suitability of particular modifications in the miniaturization context is not conclusively assessed. In order to carry out such an assessment in a reliable manner, identification of the truly optimum design is necessary. This requires rigorous numerical optimization of all antenna parameters (especially in the case of complex antenna topologies) with the primary objective being size reduction, and supplementary constraints imposed on selected electrical or field characteristics. This thesis is an attempt to carry out systematic investigations concerning the relevance of geometry modifications in the context of wideband antenna miniaturization. The studies are carried out based on selected benchmark sets of wideband antennas. In order to ensure a fair comparison, all geometry parameters are rigorously tuned through EM-driven optimization to obtain the minimum footprint while maintaining acceptable electrical performance. The results demonstrate that it is possible to conclusively distinguish certain classes of topology alterations that are generally advantageous in the context of size reduction, as well as quantify the benefits of modifications applied to various parts of the antenna structure, e.g., with feed line modifications being more efficient than the ground plane and radiator ones. Several counterexamples have been discussed as well, indicating that certain modifications can be counterproductive when introduced ad hoc and without proper parameter tuning. The results of these investigations have been utilized to design several instances of novel compact wideband antennas with the focus on isolation improvement and overall antenna size reduction in multi-input-multi-output (MIMO) systems. Experimental validations confirming the numerical findings are also provided. To the best of the author’s knowledge, the presented study is the first systematic investigation of this kind in the literature and can be considered a step towards the development of better, low-cost, and more compact antennas for wireless communication systems.Fyrir þráðlaus fjarskiptakerfi er mikilvægt að tryggja að loftnet séu lítil að umfangi. Yfirleitt er smækkun loftneta náð með ýmis konar formbreytingum á grunngerðum þeirra. Formbreytingarnar geta verið á jarðtengingu, fæðilínu og / eða geislagjafa. Því miður er venjulega einungis sagt frá slíkum formbreytingum fyrir einstaka tilvik. Skortur er á kerfisbundnu mati og samanburði á mismunandi formbreytingum og hvaða áhrif þær hafa á smækkun og raffræðilega eiginleika loftneta. Annað mikilvægt atriði, fyrir utan að ákveða gerð formbreytingarinnar, er að velja stika sem lýsa nákvæmri lögun svo að bestuð hönnun geti átt sér stað. Flestir hönnuðir notast við þá aðferð að notast við stikaskimun sem byggir á reynslugögnum, en sú aðferð skilar almennt ásættanlegri hönnun, þó ekki bestaðri. Einnig er í mörgum tilvikum sagt frá samhliða þróun fyrir og eftir formbreytingu sem leiðir til smækkunar án þess að tilgreina breytingar á stikum. Fyrir vikið er erfitt að meta til hlítar ávinning af mismunandi formbreytingum. Til þess að framkvæma slíkt mat með áreiðanlegum hætti er nauðsynlegt að geta metið bestu hönnunarútfærslu nákvæmlega. Þetta kallar á ítarlega tölulega bestun allra stika sem lýsa loftnetinu (einkum fyrir loftnet flókinnar lögunnar) þar sem aðalmarkmkið bestunar er smækkun en skorður eru settar af raffræðilegum eiginleikum. Í þessari ritgerð er leitast við að kerfisbundna rannsókn á mikilvægi formbreytingna í tengslum við smækkun bandbreiðra loftneta. Rannsóknin byggir á völdum söfnum viðmiðunarloftneta. Til að tryggja rétt mat eru allir stikar er varða lögun stilltir með rafsegulfræðilegri hermun til að tryggja minnst rúmtak með ásættanlegum raffræðilegum eiginleikum. Niðurstöðurnar sýna að unnt er að greina, án vafa, ákveðna flokka formbreytinga sem eru að jafnaði til þess fallnir að smækka loftnet. Auk þessa er hægt að reikna ávinning af formbreytingum mismunandi hluta loftnetsins, t.d. að breytingar á fæðilínu eru almennt hagkvæmari en breytingar á geislagjafa eða jarðtengingu. Þá er greint frá nokkrum tilvikum þar sem tilfallandi formbreytingar geta verið til tjóns ef ekki stikaval er ekki gert með réttum hætti. Niðurstöður þessara rannsóknar hafa verið notaðar til að hanna nokkur nýstárleg breiðbandsloftnet með áherslu á smækkun og bættan aðskilnað fjölgátta (MIMO) loftneta. Töluleg hermun er sannreynd með tilraunum. Að bestu vitund höfundar er hér um fyrstu kerfisbundnu rannsókn þessarar gerðar að ræða og má reikna með að hún leiði til þróunar betri, ódýrari og smærri loftneta fyrir þráðlaus fjarskiptakerfi.The Ph.D. project was supported by the Icelandic Research Center (RANNIS) Grant 16329905

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

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