Although it is easier to realize metamaterials in microwave frequency region for negative refractions, there was still little progress toward extensive practical applications. At microwave frequencies, potential applications include primarily (a) substrate materials for antenna and microwave component designs and fabrications, and (b) absorbing materials for engineering and radar applications. There are, however, still primarily fundamental issues or limitations of metamaterials at microwave frequencies: narrow bandwidth (when both negative permittivity and negative permeability fall within the same band) and high loss (due to the ohmic loss and especially radiation loss of inclusion elements), and this drawbacks become especially serious and severe when the SRR- and other inclusion-types of metamaterials are used as substrate of the patch antenna. The present talk will address these fundamental issues and thereafter brief some recent advances of the matamaterial microstrip antennas and arrays which were achieved by employing the negative permittivity and permeability concepts. With this implementation, it is to demonstrate that the bandwidth and gain of conventional microstrip antennas and their arrays can be significantly enhanced by applying the planar metamaterial patterned structures directly on the upper array elements and the bottom ground of the dielectric substrate, so that the antennas and arrays can have much high performance.

Joshua Le-Wei Li received his Ph.D. degree in Electrical Engineering from Monash University, Melbourne, Australia, in 1992. Since 1992, he has been with the Department of Electrical & Computer Engineering at the National University of Singapore where he is currently a Full Professor. In 1999-2004, he was seconded to High Performance Computations on Engineered Systems (HPCES) Programme of Singapore-MIT Alliance (SMA) as a Course Coordinator and SMA Faculty Fellow. In May-July 2002, he was a Visiting Scientist with Research Laboratory of Electronics at Massachusetts Institute of Technology; and in October 2006, he was an Invited Visiting Professor with University of Paris VI, France. He was an Invited Visiting Professor with Institute for Transmission, Waves and Photonics at Swiss Federal Institute of Technology, Lausanne (EPFL) between January and June 2008 in Switzerland. In March 2010, he also joined University of Electronic Science and Technology of China in Chengdu as a Qian-Ren Talent Scheme Chair Professor and Founding Director of Institute of Electromagnetics. His current research interests include electromagnetic theory, computational electromagnetics, radio wave propagation and scattering in various media, microwave propagation and scattering in tropical environment, and analysis and design of various antennas. In these areas, he has (co-)authored a book, Spheroidal Wave Functions in Electromagnetic Theory (New York: Wiley, 2001), 48 book chapters, over 310 international refereed journal papers, 48 regional refereed journal papers, and over 350 international conference papers. Prof. Li received a number of awards from various professional bodies or institutions. He has been a Fellow of IEEE since 2005, and a Fellow of The Electromagnetics Academy since 2007 (selected member since 1998). He also serves as a Guest Editor, an Associate Editor and an (Overseas) Editorial Board Member several international and regional archival technical journals.

In millimeter wave and sub-millimeter wave remote sensing and radio-astronomy applications, several quasi-optical (QO) reflectors are cascaded to form a feed system to the main antenna. Such Quasi-Optical antenna systems are used at increasingly high frequencies up to and into the THz-region. The latest launched Planck and Herschel telescopes operating in the frequency bands of 30-857GHz and 448 – 5.3THz, respectively, posed many challenges in designing their QO systems. This talk will give a brief overview of the Planck and Herschel missions and their related engineering challenges in radiometry at first. Then, the talk will introduce a fast design technique for analyzing complex quasi-optical systems developed at Queen Mary, University of London and Beijing University of Posts and Telecommunications. The design and analysis technique in question is a combination of two numerical methods, i.e. the Diffracted Gaussian Beam mode Analysis (DGBA) to transport signal beams between focusing reflectors while accounting for edge diffraction and the Periodic Method of Moments (PMM) to compute the emergent beam fields of either transmission and/or reflection for signal conditioning components interleaved between reflectors. The talk will also presents the experimental verification of this design and analysis technique based on a number of Quasi-optical systems, including a tri-reflector Compact Antenna Test Range (CATR) which was aimed for THz antenna system metrology.

Linear Power amplifiers become very a hot issue for the mobile communication. The performance of the unit PAs is improved significantly using GaN technology. The class E, J, F and saturated amplifiers are heavily researched. To improve the performance further, the unit amplifiers are utilized in transmitter architectures such as Doherty amplifier, Envelope Tracking, and class-S. These advanced architectures will be introduced. Finally, the digital predistortion technique will be discussed, which is the main linearization technique of the transmitters.