Over the past several years, one of the major directions of research at Professor Itoh’s group has been microwave applications of metamaterial structures. Metamaterials are artificially synthesized structures which exhibit unique and unusual electromagnetic properties not found in nature. Specifically, of the metamaterials, the so-called negative index materials have been of interest. Although most demonstrations of negative index materials have been based on resonant structures, Professor Itoh’s group has taken a different approach. They have introduced along with several other microwave groups the transmission line type of metamaterials which are of low loss and broad band since they do not depend on the resonance. Such properties as broadband and low loss are attractive in developing microwave components with unique features.
Specifically, Professor Itoh’s group has pioneered the transmission line type metamaterials called the Composite Right/Left Handed (CRLH) structures. This artificial structure has a periodic configuration with its unit cell consisting of equivalences of series inductance, series capacitance, shunt inductance and shunt capacitance. The dispersion relationship is nonlinear and engineerable by controlling the unit cell. At low frequencies, the CRLH exhibits negative index behavior (or backward wave) while at higher frequencies it provides positive index behavior (or forward wave propagation).
Based on this new paradigm, various microwave components and antennas with unique feature have been demonstrated. Some examples are miniaturized antennas, filters and diplexers, dual frequency components, full space scanning leaky wave antennas and infinite wavelength antennas, active antennas with high power added efficiency, and dual frequency CMOS oscillators.
Recent effort along the CRLH structures include enhanced versions of leaky wave antennas include dual and circularly polarized LWA, electronically controlled conformal LWA and active LWA with distributed amplifiers. Several versions of miniature antennas with and without CRLH concepts have been carried out. One of them is UHF and HF antennas based on periodically loaded slow wave structures while others are based on dual polarization Ku band omni-directional antennas.
More recently, the group has successfully demonstrated nondestructive testing of nano-scale mechanical vibrations by way of microwave interferometers. The method was also successful in detecting a shock wave.
The group receives strong financial support from various agencies and industries. They include Office of Naval Research, NASA, NSF, SONY, Honeywell, Panasonic, NEC, Mitsubishi, Lockheed Martin, Northrop Grumman, BossaNova, Pharad and Rayspan. Several agencies and industries provided funds for travel.
PROFESSIONAL AND INTERNATIONAL ACTIVITIES
Professor Itoh has continued to be active in professional activities, particularly IEEE Microwave Theory and Technique for which he has been a member of Administrative Committee as an Honorary Life Member. He has been involved in a number of activities such as Nominations and Appointment, Award, and ad hoc activity related to Asia Pacific Microwave Conference. He has served as Chairman of Technical Program Committee for 2007 International Microwave Symposium. He is MTT Representative to USNC of URSI. He serves as Member of General Assembly for European Microwave Association representing North America. He is a member of International Steering Committee for Asia Pacific Microwave Conference. Recently, his has established a strong tie to National Taiwan University as Special Research Chair and to Tokyo Institute of Technology as an Advisory Board member for Graduate Program. He collaborates with a number of institutes including Kyoto Institute of Technology, National Taiwan University, JAXA in Japan and INAOE in Mexico. His lab is frequently visited by short and long term visitors.
Professor Itoh received Outstanding Career Award from European Microwave Association.