March 21, 2012

Multifunctional Structural Composites for Antenna Integration

Professor Mark Mirotznik

Bio

Professor Mark S. Mirotznik received the B.S.E.E. degree from Bradley University, Peoria, IL, in 1988 and the M.S.E.E. and Ph.D. degrees from the University of Pennsylvania, Philadelphia, in 1991and 1992, respectively.  From 1992 to 2009, he was a faculty member in the Department of Electrical Engineering at The Catholic University of America, Washington, DC.  Since 2009 he is an Associate Professor and Director of Educational Outreach in the Department of Electrical and Computer Engineering at the University of Delaware, Newark DE.  In addition to his academic positions he an associate editor of the Journal of Optical Engineering and also holds the position of Senior Research Engineer for the Naval Surface Warfare Center (NSWC), Carderock Division.  He is the recipient of the 2010 Wheeler Prize Award for Best Application Paper in the IEEE Transactions on Antennas and Propagation.  His research interests include applied electromagnetics, computational electromagnetics and multifunctional materials.networks and dielectric loading of the composite's polymer matrix.

Abstract

Woven fabric composites are a popular core building block material of many commercial and military platforms.  The composite's high strength to weight ratio, low cost and good thermal properties are among some reasons for their popularity.  Conventional composites are composed of layers of woven fabrics, usually consisting of glass, polymer or carbon fibers that are held together by a polymer matrix or resin.  Decades of military, academic and industrial research have gone into the design and manufacturing of composites whose mechanical properties are optimized.  Much more recently, material researchers have begun to investigate ways to create composites that have other attractive material properties beyond their mechanical strength, such as electromagnetic (EM) properties.  By tailoring the electromagnetic properties of structural composites it may be possible to integrate antennas, create wideband structural radomes, develop RF transparent armor, embed frequency selective surfaces as well as other electromagnetic components directly into the structural skin of future commercial and military vehicles and structures.

In this presentation Professor Mirotznik will discuss a number of computational and experimental methods used for the design and fabrication of structural composites with attractive electromagnetic properties.  Examples include texturing the composite's surface for wideband impedance matching (e.g. moth-eye approach), integration of 3D conductor networks and dielectric loading of the composite's polymer matrix.

April 17, 2012 

Heinz Wipf received his Ing. HTL diploma (BSEE) in communication and computer science from the Technikum in Winterthur Switzerland. He holds additional degrees in electromagnetic compatibility, applied statistics, technology management and economics from the Swiss Institute of Technology in Lausanne and Zurich. Since 1982 he is working with the Swiss Air Navigation Services Ltd. primarily in the fields of navigation, business development and program management both operational and technical. Before he has been with Siemens in research and development working on private branch exchanges. He is currently holding two part time position as lecturer in communication and navigation systems at the University of Applied Science in Zurich and Winterthur. He is a member of the IEEE and AIAA. He has participated in a number of international working groups. He is a patent owner and active as an expert witness on oath in Austria.

Given a fully approved flight calibration aircraft with standard instrument landing systems antennas, it can be shown that the receiving pattern of the aircraft antenna in conjunction with a standard instrument landing systems antenna array in a typical multipath environment may have a considerable impact on the data collected.

The results shown stem from realistic electromagnetic field computations on a typical flight calibration aircraft. The context is from measurements conducted on a major Swiss airport.

The 3d antenna diagrams will be compared to free space pattern. Results for some scenarios are presented. 

Arun K. Bhattacharyya received his B.Eng. degree in electronics and telecommunication engineering from Bengal Engineering College, University of Calcutta in 1980, and the M.Tech. and Ph.D. degrees from Indian Institute of Technology, Kharagpur, India, in 1982 and 1985, respectively.

From November 1985 to April 1987, he was with the University of Manitoba, Canada, as a Postdoctoral Fellow in the electrical engineering department. From May 1987 to October 1987, he worked for Til-Tek Limited, Kemptville, Ontario, Canada as a senior antenna engineer. In October 1987, he joined the University of Saskatchewan, Canada as an assistant professor of electrical engineering department and then promoted to the associate professor rank in 1990. In July 1991 he joined Boeing Satellite Systems (formerly Hughes Space and Communications), Los Angeles as a senior staff engineer, and then promoted to scientist and senior scientist ranks in 1994 and 1998, respectively. Dr. Bhattacharyya became a Technical Fellow of Boeing in 2002. In September 2003 he joined Northrop Grumman Space Technology group as a staff scientist, senior grade. He became a Distinguished Engineer which is a very rare and honored recognition in Northrop Grumman. He is the author of “Electromagnetic Fields in Multilayered Structures-Theory and Applications”, Artech House, Norwood, MA, 1994 and “Phased Array Antennas, Floquet Analysis, Synthesis, BFNs and Active Array Systems”, Hoboken, Wiley, 2006. He authored over 95 technical papers, 4 book-chapters and has 15 issued patents. His technical interests include electromagnetics, printed antennas, multilayered structures, active phased arrays and modeling of microwave components and circuits. 

Dr. Bhattacharyya became a Fellow of IEEE in 2002. He is a recipient of numerous awards including the 1996 Hughes Technical Excellence Award, 2002 Boeing Special Invention Award for his invention of High Efficiency horns, 2003 Boeing Satellite Systems Patent Awards and 2005 Tim Hannemann Annual Quality Award, Northrop Grumman Space Technology.

Professor Jin-fa Lee

Professor Jin-Fa Lee received the B.S. degree from National Taiwan University, in 1982 and the M.S. and Ph.D. degrees from Carnegie-Mellon University in 1986 and 1989, respectively, all in electrical engineering. From 1988 to 1990, he was with ANSOFT Corp. (currently a subsidiary of ANSYS Inc.), where he developed several CAD/CAE finite element programs for modeling threedimensional microwave and millimeter-wave circuits. From 1990 to 1991, he was a post-doctoral fellow at the University of Illinois at Urbana- Champaign. From 1991 to 2000, he was with Department of Electrical and Computer Engineering, Worcester Polytechnic Institute. Currently, he is a Professor at ElectroScience Lab., Dept. of Electrical and Computer Engineering, The Ohio State University. Prof. Lee becomes an IEEE Fellow on year 2005 and serves as an associate editor since 2007 for IEEE Transaction on Antenna Propagation. Moreover, he is serving as a Distinguished Lecturer, term 2011- 2013, for IEEE Antenna Propagation Society. Also, he is a member of the Board of Directors for Applied Computational Electromagnetic Society (ACES). Dr. Lee is a special appointed professor of Yuan-Ze University, Taiwan, and a visiting professor of National mUniversity of Singapore. Among the honors and awards that Dr. Lee received over the years are: a fellow of Electromagnetic Academy; a Yuan-Ze Special-Appointed Professor, Yuan-Ze University, Taiwan; the recipient of 1992 Joseph Samuel Satin Distinguished Fellow Award, WPI; the 1st International Famous Professor to Beijing Institute of Technology (BIT), 2007; the recipient of the College Engineering Lumley Research Award, Ohio State University, 2006 and 2011; the recipient of the Distinguished Scholar Award from the Ohio State University, 2012; a holder of the Chair of Excellence of Spain 2012-2013, Universidad Carlos III de Madrid, Spain; a MINDEF visiting scientist Singapore, 2010; co-author of ACES 2009 best paper award; and the supervisor of many best student papers of international symposiums and conferences.

Dr. Lee’s research interests mainly focus on numerical methods and their applications to computational electromagnetics. Current research interests include: analyses of numerical methods, fast finite element methods, fast integral equation methods, domain decomposition methods, hybrid numerical methods and high frequency techniques based on domain decomposition approach, LCD modeling, large antenna arrays, multi-physics simulations and modeling, and co-design for signal integrity and packaging

Abstract

Modern antenna engineering often involves the use of meta-materials, complex feed structures, and conformally mounting on large composite platforms. However, such antenna systems do impose significant challenges for numerical simulations. Not only do they usually in need of large-scale electromagnetic field computations, but also they tend to have many very small features in the presence of electrically large structures. Such multi-scale electromagnetic problems tax heavily on numerical methods (finite elements, finite difference, integral equation methods etc.) in terms of desired accuracy and stability of mathematical formulations.

 In this lecture, Professor Lee will present his on-going efforts in combating the multi-scale electromagnetic applications, both scattering and radiation problems through the use of non-conventional PDE methods that are non-conformal. The non-conformal numerical methods relax the constraint of needing conformal meshes throughout the entire problem domain. Consequently, the entire system can be broken into many sub-problems, each has its own characteristics length and will be meshed independently from others. Particularly, our discussions will include the following topics:

 Integral Equation Domain Decomposition Method (IE-DDM): A very significant breakthrough that has been accomplished is the IE-DDM formulation. For example, Professor Lee will show an electromagnetic plane wave scattering from a mock-up fighter jet with thin coatings at the X- and Ku-bands by dividing the platform into many closed objects, and noting that they will be touching each other through common interfaces.

 Non-Conformal DDM with Higher Order Transmission Conditions and

Corner Edge Penalty: By introducing two second-order transverse derivatives, one for TE and one for TM, the derived 2nd order TC provides convergence for both the propagating and evanescent modes. Moreover, on the corner edges sharing by more than two domains, an additional corner edge penalty term needs to be added in the variational formulation. Consequently, the robustness of the non-conformal DDMs is now firmly established theoretically and numerically.

 Multi-region/Multi-Solver DDM with Touching Regions: Many multi-scale physical problems are very difficult, if not impossible, to solve using just one of the existing CEM techniques. We have been pursuing a multi-region multi-solver domain decomposition method (MS-DDM) to effectively tackle such problems. Various CEM solvers are now integrated into a MS-DDM code and collectively, it emerges as the only alternative for solving many real-life applications that were thought un-solvable

October 5, 2012

First Seminar: Analyses of spherical antennas

Second Seminar: Development of Dielectric Resonator Antenna

Professor K W Leung

Bio

Professor K W Leung was born in Hong Kong. He received the B.Sc. degree in Electronics and Ph.D. degree in electronic engineering from the Chinese University of Hong Kong, in 1990 and 1993, respectively.

From 1990 to 1993, he was a Graduate Assistant with the Department of Electronic Engineering, the Chinese University of Hong Kong. In 1994, he joined the Department of Electronic Engineering at City University of Hong Kong (CityU) and is currently a Professor and an Assistant Head of the Department. He is also the founding Director of the Innovation Centre of the Department. From Jan. to June, 2006, he was a Visiting Professor in the Department of Electrical Engineering, The Pennsylvania State University, USA.

Professor Leung was the Chairman of the IEEE AP/MTT Hong Kong Joint Chapter for the years of 2006 and 2007. He was the Chairman of the Technical Program Committee, 2008 Asia-Pacific Microwave Conference, Hong Kong, the Co-Chair of the Technical Program Committee, 2006 IEEE TENCON, Hong Kong, and the Finance Chair of PIERS 1997, Hong Kong. His research interests include RFID tag antennas, dielectric resonator antennas, microstrip antennas, wire antennas, guided wave theory, computational electromagnetics, and mobile communications. He was an Editor for HKIE Transactions and a Guest Editor of IET Microwaves, Antennas and Propagation. Currently, he serves as an Associate Editor for IEEE Transactions on Antennas and Propagation and received Transactions Commendation Certificates twice in 2009 and 2010 for his exceptional performance. He is also an Associate Editor for IEEE Antennas and Wireless Propagation Letters. He has been appointed as a Distinguished Lecturer by the IEEE Antennas and Propagation Society for 2012-2014

Presentation 1

Presentation 2

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Abstract

First Seminar: Analyses of spherical antennas

The spherical antenna is an interesting and useful topic. For example, a spherical helical antenna can radiate circularly polarized fields over a wide beamwidth. An antenna array with its elements distributed over a spherical surface is able to determine the direction-of-arrival and polarization of an incoming wave. Further, a spherical antenna array can be used to avoid the scanning problem of a planar array at low elevation.

The spherical antenna is also important from the theoretical point of view. Since a spherical structure does not have any edge-shaped boundaries as found in cylindrical and rectangular structures, its closed-form Green’s function is obtainable. As a result, an exact solution of a spherical problem can exist, and the solution can be used as a reference for checking the accuracy of numerical or approximation techniques.

In this talk, the general solution of Helmholtz equation in the spherical coordinates will be briefly reviewed. The solution will be used to solve different spherical antenna problems, including the spherical slot antenna, spherical microstrip antenna, and grounded hemispherical dielectric resonator antenna (which is equivalently a dielectric sphere after imaging). Derivations of their exact modal Green’s functions will be described. Both electric and magnetic current sources will be considered, and their integral equations will be formulated using the Green’s functions. The method of moments (MoM) will be used to solve for the electric or magnetic current sources. From the currents, the input impedances and radiation patterns of the spherical antennas can be obtained easily.

When a field point coincides with a source point, the Green’s functions will become singular and care has to be exercised in evaluating their MoM integrals. Around a singular point, an extensive number of modal terms are needed to calculate the Green’s functions accurately. This may lead to practical problems because amplitudes of high-order Hankel functions can be too large to be handled numerically. A method that tackles the singularity problem will be presented. In this talk, integrals involving spherical Bessel functions or associate Legendre functions will be evaluated rigorously through analytical integration or their recurrence formulas. Since numerical integration is avoided, the evaluations of the integrals are computationally very efficient. Numerical convergence of the modal solutions will also be examined. Excellent agreement between theory and experiment is observed and the results will be presented in the talk. Finally, it will be shown that a spherical solution can be used to solve a planar annular problem.

only alternative for solving many real-life applications that were thought un-solvable

Second Seminar: Development of Dielectric Resonator Antenna

The fundamentals and development of dielectric resonator antenna will be discussed in this talk. For many years, dielectric resonators (DRs) have only been used as high-Q elements in microwave circuits until S. A. Long and his collaborators showed that they can also be used as efficient radiators. The studies were motivated by an observation that carrier frequencies of modern wireless systems had gradually progressed upward to the millimeter-wave region, where efficiencies of metallic antennas can be reduced significantly due to the skin effect. In contrast, DR antennas (DRAs) are purely made of dielectric materials with no conductor loss. This feature makes DRAs very suitable for millimeter-wave systems.

As compared to the microstrip antenna, the DRA has a much wider impedance bandwidth (~ 10% for dielectric constant ~ 10). This is because the microstrip antenna radiates only through two narrow radiation slots, whereas the DRA radiates through the whole DRA surface except the grounded part. Avoidance of surface waves is another attractive advantage of the DRA over the microstrip antenna. Nevertheless, the DRA and microstrip antenna have many common characteristics because both of them are resonators. For example, both of them can be made smaller in size by increasing the dielectric constant because the dielectric wavelength is smaller than the free-space wavelength. Furthermore, basically all excitation methods applicable to the microstrip antenna can be used for the DRA.

Although the DRA received attention originally for millimeter-wave applications, it is also widely investigated at microwave or even RF frequencies. It is because the DRA is a volume device that offers designers more degrees of freedom than 2D-type antennas (e.g., microstrip antennas) or 1D-type antennas (e.g., monopole antennas). Other advantages of the DRA include its light weight, low cost, low loss, and ease of excitation.

The following DRA topics will be covered in this talk:    

Basic theory
Frequency-tuning techniques
Circularly polarized DRAs
Dualband and wideband DRAs
Dualfunction DRAs
Omnidirectional DRAs
Higher-order-mode DRAs