小型衛星搭載の合成開口レーダー用の集中型送受信システムを有する２偏波対応進行波型アンテナ

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 齋藤 宏文, 東京大学教授 橋本 樹明, 東京大学教授 保立 和夫, 東京電機大学教授 小林 岳彦, 東京工業大学教授 廣川 二郎University of Tokyo(東京大学

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

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

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Síntesis óptima de diagramas de radiación utilizando agrupaciones planas de antenas

En esta tesis se ha estudiado la síntesis de diagramas de radiación en campo lejano de agrupaciones o arrays de antenas planas. Dichas agrupaciones resultan interesantes ya que presentan claras ventajas respecto a otras configuraciones: permiten un control preciso del haz del lóbulo principal y un aumento de la ganancia, entre otras características. Con este motivo, en el desarrollo de esta tesis doctoral, se han estudiado diversos métodos de síntesis de agrupaciones de antenas, pudiendo incluso permitir controlar el contorno de la superficie a radiar mediante la creación de diagramas footprint o tipo huella. En todos los estudios llevados a cabo se ha buscado controlar no sólo el nivel de lóbulos laterales sino también el rizado (en diagramas de haz perfilado). Así mismo, se ha tenido especial cuidado en obtener relaciones de rango dinámico no demasiado elevadas y valores de directividades adecuados

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

Space-Air-Ground Integrated 6G Wireless Communication Networks: A Review of Antenna Technologies and Application Scenarios

A review of technological solutions and advances in the framework of a Vertical Heterogeneous Network (VHetNet) integrating satellite, airborne and terrestrial networks is presented. The disruptive features and challenges offered by a fruitful cooperation among these segments within a ubiquitous and seamless wireless connectivity are described. The available technologies and the key research directions for achieving global wireless coverage by considering all these layers are thoroughly discussed. Emphasis is placed on the available antenna systems in satellite, airborne and ground layers by highlighting strengths and weakness and by providing some interesting trends in research. A summary of the most suitable applicative scenarios for future 6G wireless communications are finally illustrated

Advanced Radio Frequency Antennas for Modern Communication and Medical Systems

The main objective of this book is to present novel radio frequency (RF) antennas for 5G, IOT, and medical applications. The book is divided into four sections that present the main topics of radio frequency antennas. The rapid growth in development of cellular wireless communication systems over the last twenty years has resulted in most of world population owning smartphones, smart watches, I-pads, and other RF communication devices. Efficient compact wideband antennas are crucial in RF communication devices. This book presents information on planar antennas, cavity antennas, Vivaldi antennas, phased arrays, MIMO antennas, beamforming phased array reconfigurable Pabry-Perot cavity antennas, and time modulated linear array