Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.

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Electromagnetic Band Gap Structures in Antenna Engineering

Inter es de la investigaci on: En los ultimos a~nos hemos asistidoa la aparici on de aplicaciones comerciales a frecuencias elevadas,como son la parte alta de la banda de microondas y las bandas demilim etricas y submilim etricas, y se espera un incremento en lospr oximos a~nos. Esta creciente demanda exige un r apido desarrollode tecnolog a de bajo coste con buenas prestaciones a estas frecuencias,donde las tecnolog as m as comunes, como son la tecnolog amicrostrip y las gu as de onda, presentan algunas de ciencias. Enconcreto, las soluciones existentes para antenas planas de barridode alta ganancia a estas frecuencias sufren los inconvenientes dedichas tecnolog as y dan lugar a productos con un coste demasiadoalto para su producci on masiva.Objetivos: El objetivo principal de la presente tesis doctoral consisteen estudiar la viabilidad de una nueva propuesta que mejorelas soluciones existentes hasta la fecha en lo referente a antenasplanas de barrido de alta ganancia y bajo coste a frecuencias elevadas.Este objetivo global ha desembocado en otro objetivo centralde esta tesis que consiste en la investigaci on de nuevas gu ascuasi-TEM m as apropiadas que las tecnolog as actuales para la realizaci on de circuitos y componentes en estas bandas de frecuencia.Estas soluciones guiadas hacen uso de super cies peri odicas o arti -ciales con la nalidad de con nar y dirigir los campos en el interiorde estas gu as.Metodolog a: El trabajo desarrollado sigue una secuencia l ogicade tareas espec cas encaminadas a la consecuci on del objetivo principalde esta tesis. En el cap tulo 2 se presenta la soluci on guiadapropuesta y se muestra su funcionamiento num erica y experimentalmente.El dise~no optimizado de antenas de alta ganancia basadasen agrupaciones de ranuras en gu a exige el desarrollo de c odigospropios e cientes. La implementaci on y validaci on de este c odigo sepresenta en el cap tulo 3, donde se propone un nuevo m etodo parael an alisis de super cies corrugadas, y en el cap tulo 4, donde seextiende este c odigo para el an alisis de agrupaciones de ranuras engu a. El proceso de dise~no y optimizaci on de una agrupaci on bidimensionalse describe en el cap tulo 5, donde se expone tambi enuna validaci on experimental preliminar. Por otra parte, la soluci onguiada propuesta ha inspirado la aparici on de una tecnolog a guiadacon mayor ancho de banda y m as vers atil para la realizaci on de circuitosy componentes a frecuencias elevadas. El cap tulo 6 presentalas contribuciones realizadas al estudio de esta tecnolog a y a suaplicaci on en el dise~no de circuitos.Resultados: Se ha demostrado num erica y experimentalmente quelas dos estructuras guiadas estudiadas aqu , una ideada como soportede una agrupaci on de ranuras, y la otra especialmente interesantepara la realizaci on de circuitos y componentes, presentanunas caracter sticas particulares que les con eren un gran potencialpara su aplicaci on en antenas y circuitos a frecuencias elevadas. Elestudio de viabilidad culmina con el dise~no de una agrupaci on deranuras bidimensional en la gu a propuesta. Para este dise~no se haempleado un c odigo propio e ciente basado en un m etodo nuevopara el an alisis de super cies corrugadas, el cual constituye una delas aportaciones principales de este trabajo. La aplicaci on de lasegunda estructura guiada en la realizaci on de circuitos se ha demostradomediante el dise~no, fabricaci on y medida de circuitos demicroondas.

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New quasi-TEM waveguides using artificial surfaces and their application to antennas and circuits

Overview In recent years, electromagnetic band gap (EBG) structures have attracted increasing interest in the electromagnetic community. Because of their desirable electromagnetic properties, they have been widely studied for potential applications in antenna engineering. Hundreds of EBG papers have been published in various journals and conferences. To illustrate the rapid increase of research interest, a simple search using the keywords “EBG” and “antenna” was performed on IEEE Xplore on 1/18/2008 and the data are plotted in Fig. A.1 based on the available number of publications. It is clear that the number of papers has steadily increased over the years with an apparent peak of publications in 2005. Here we provide a comprehensive overview of these publications so that readers can establish a clear picture of EBG development. It will also help readers to easily find papers related to their own research interests. Since the scope of this book is EBG metamaterials, papers on double negative property, left-handed propagation, and negative refractive index are not covered in this overview. We also regret if we have missed some papers as there have been so many international conferences with sessions on this topic. To start with, we would like to emphasize several special issues organized in microwave and antenna journals that relate to EBG research. These special issues provide the readers with background and information for EBG research. They summarize the latest research progress at the time of publication, and have greatly stimulated EBG research afterwards.

Electromagnetic Band Gap Structures in Antenna Engineering: Appendix: EBG literature review

The present work focuses on the study of bandgaps of soft surfaces in the form of metal strips printed on grounded dielectric slabs when the strips are provided with a metal connection to the ground plane. We can refer to such a structure as a modern realization of cavity loaded corrugations. In particular, the dispersion properties of the surface wave are investigated in order to find the bandgap.

Numerical investigation of bandgaps of different soft surfaces: corrugations and strip loaded substrate with vias

Size reduction is one of the most important considerations for wireless personal communication system antennas In many cases, the main problem is the reduction of ground plane size Such reduction means an increase in antenna back radiation EBG (electromagnetic bandgap) surfaces have been used as ground planes Soft and hard surfaces are defined in terms of surface impedance and boundary conditions in the E- and H-planes A soft surface behaves like a PEC in the H-plane and as a PMC in the E-plane, thereby providing ideally infinite bandgaps in both E- and H-planes Therefore, they also reduce antenna back radiation in the E-plane A study of different soft surface ground planes has been made All the analyzed structures have been demonstrated to work as expected A bandwidth study is presented The results show an important conclusion: although the theoretical bandgap of these structures can be very large, this does not mean that for a particular application (in this case ground plane) the bandwidth is large as well For strip-loaded surfaces with vias, it was only possible to get very low back radiation in a narrow frequency band around the best 'soft' frequency, ie the start of the bandgap This best 'soft' frequency is slightly lower than the theoretical 'soft' frequency

Jiang Yang

Papers

Comparison between bandgaps and bandwidths of back radiation of different narrow soft ground planes