IEEE Distinguished Lecturer Series
IEEE DISTINGUISHED LECTURER SERIES
Reconfigurable Multifunctional Antennas
&
RF/Photonic Antennas
By
Prof. Christos G. Christodoulou
University of New Mexico, ECE Department
• Monday,April 7,2008/13.40-15.30, FENS L048-Sabancı University-Istanbul
(Reconfigurable Multifunctional Antennas)
• Tuesday,April 8,2008/10.30-12.00, EB 208-Koc University-Istanbul
(RF/Photonic Antennas)
• Wednesday,April 9,2008/15.45-17.00, EA 409- Bilkent University-Ankara
(RF/Photonic Antennas)
• Thursday,April 10,2008/10.30-12.00, Sevim Tan Auditorium- Middle East Technical University -Ankara
(Reconfigurable Multifunctional Antennas)
Reconfigurable Multifunctional Antennas
Abstract
The requirements for increased functionality, such as direction finding, radar, control and command, within a confined volume, place a greater burden in today’s transmitting and receiving systems. A solution to this problem is the re-configurable antenna. Antennas that can be used for multiple purposes that function over several frequency bands and that can be integrated on a package for mass-production is the ultimate goals of commercial and defense investigators. Furthermore, applications of such systems in personal and satellite communications impose the requirement for elements miniaturized in size and weight.
Key-elements to obtain reconfigurability in many RF circuits are the Radio-Frequency MicroElectroMechanical Systems (RF-MEMS). Even though RF-MEMS have been used in the past to reconfigure filters, phase-shifters, capacitors and inductors, their integration in an antenna system has been limited as it faces a plethora of issues that need to be resolved. The absence of a reconfigurable RF-MEMS antenna system and the recent advances in fractal - and especially Sierpinski gasket- antennas combined with the availability of series cantilever RF-MEMS switches, sparked the pioneering idea to design a multiple-frequency antenna that will radiate on-demand the same radiation pattern at various frequencies. Such a system was designed and successfully implemented, as the first functional, fully integrated RF-MEMS reconfigurable self-similar antenna.
In this talk, several reconfigurable antennas are presented and discussed. The antennas to be presented cover a wide range of designs such as fractal antennas, triangular antennas, dipoles and monopoles with variable sleeves. All these antennas make use of MEMS switches, to make them reconfigurable. Some of the challenges that the designer has to face in biasing and integrating these switches with the antenna has are also presented and discussed.
RF/Photonic Antennas
The need for more bandwidth and capacity in wireless systems currently is the main culprit for the great interest in the development of wireless communications systems operating at millimeter wave frequencies and higher. The future needs of broad-band interactive services (1Gb/s) demand the application of optical fiber feed networks for distribution of the radio signals to and from the antennas at the various base stations. Fiber-optic technologies have reached the stage where insertions into various commercial RF systems are being considered.
Today, there are three main steps in the evolution of RF/Photonics systems for wireless communications. The first step has been in the direction of using photonics to slowly replace conventional RF components, such as, the coax that is used to interconnect the antenna to the electronics. Optical fibers, in contrast to coaxial cable, provide a more ideal medium for broadband RF communication systems. The light weight property of fibers and its immunity from other signal interference make them very critical in the development of future RF distribution systems. The second, and more challenging step, is in the seamless integration of photonics and RF wireless circuits. The challenge in this step is to use photonics and RF circuits as complementary systems and blend them together. Finally, the third step is towards the development of optically coupled antennas (RF/photonic antennas). In this step the aim is to eliminate the need of local oscillators, mixers, amplifiers and a host of other parts by directly feeding an antenna through a fiber at millimeter wave frequencies.
In this talk, several examples of RF/Photonic antennas are presented and discussed. It is essentially a marriage of microwave and optical techniques. The antennas are coupled to either RF modulator/photodetectors or to Quantum Dot lasers. The integrated units can then be used as a cellular block in more complex antenna arrays which can be controlled using field programmable gate arrays (FPGA).
Biography
Christos G. Christodoulou received his Ph.D. degree in Electrical Engineering from North Carolina State University in 1985. He served as a faculty member in the University of Central Florida, Orlando, from 1985 to 1998. In 1999, he joined the faculty of the Electrical and Computer Engineering Department of the University of New Mexico, where he served as the Chair of the Department from 1999 to 2005. He is a Fellow member of IEEE and a member of Commission B of USNC/URSI, Eta Kappa Nu and the Electromagnetics Academy. He served as the general Chair of the IEEE Antennas and Propagation Society/URSI 1999 Symposium in Orlando, Florida, as the co-chair of the IEEE 2000 Symposium on Antennas and Propagation for wireless communications, in Waltham, MA, and the co-technical chair for the IEEE Antennas and Propagation Society/URSI 2006 Symposium in Albuquerque.
Currently, he is an associate editor for the AWPL, the International Journal of RF and Microwave Computer-aided Engineering, and the IEEE Antennas and Propagation Magazine. He was appointed as an IEEE AP-S Distinguished Lecturer (2007-2009) and elected as the President for the Albuquerque IEEE Section. He served as a associate editor for the IEEE Transaction on antennas and Propagation for six years, as a guest editor for a special issue on “Applications of Neural Networks in Electromagnetics” in the Applied Computational Electromagnetics Society (ACES) journal, and as the co-editor of a the IEEE Antennas and Propagation Special issue on “Synthesis and Optimization Techniques in Electromagnetics and Antenna System Design” (March 2007). He has published about 300 papers in journals and conferences, has 11 book chapters and has co-authored 4 books.
His research interests are in the areas of modeling of electromagnetic systems, reconfigurable systems, machine learning applications in electromagnetics, and smart RF/photonic antennas.