Transmission Line Mode Theory for Small Antennas

Keisuke Noguchi
Kanazawa Institute of Technology

Tuesday, August 24, 2010 at 10:00am
Engr IV Faraday Room 67-124

Abstract

As development of built-in technology is in great demand in wireless communication systems, small antennas mounted in terminals with multiband/wideband characteristics are increasingly required. In order to realize small antennas with multiband/wideband characteristics, antennas consisting of several wires, strip conductors and slots are designed. Design of these antennas consisting of multiconductor depends on EM simulator because of complicated mutual coupling between conductors. EM simulator is certainly powerful for antennas design, however, trial and error is needed and it takes a long time to obtain desirable antenna characteristics. Therefore, a simple initial design concept is strongly recommended for effective design of multiband/wideband small antennas.

Theory of multiwire transmission line was developed by L. M. Wedepohl, and it is well known in the field of power electronics. The theory based on matrix method and orthogonal modes with eigenvalue is applied for analysis of multiwire transmission line systems. Antennas with multiwire have also been analyzed by H. Uchida, whose proposed antennas include from two to four conductors. In this presentation, matrix method based on orthogonal modes, the transmission line mode theory, is discussed theoretically which can be used for applications like facilitating small antenna design.

Expansion of the above theories simplifies the design of multiband/wideband small antennas. The recent articles using the theory of characteristic modes proposed by M. Cabedo-Fabres help in designing multiresonant antennas. However, a simpler approach is required to design modern multiband/wideband small antennas. As a representative example, an E-shaped patch antenna is characterized as a multiband/wideband antenna with orthogonal modes. Three basic modes exist for an E-shaped patch (one radiation mode and two transmission line modes). The antenna is analyzed based on current distributions in modes. The impedance characteristics are analyzed and a practical design for multiband/wideband characteristics is attempted.

Biography
Prof. Keisuke Noguchi received the B.E. and D.Eng. degrees in electrical engineering from the Kanazawa Institute of Technology, Ishikawa, Japan, in 1990 and 1998, respectively, and the M.E. degree in electrical engineering from Tohoku University, Sendai, Japan, in 1992. From 1992 to 1995, he worked with the Central Research Laboratory of Hitachi, Ltd. Since 1995, he has been with the Department of Information and Communication Engineering at Kanazawa Institute of Technology, where he is presently a Professor. His main research interests include antennas and propagation for personal communication applications. In particular, his research has focused on small antennas such as helical, meander-line and dielectric resonator antennas. He is a member of the IEEE and the Institute of Electrical, Information and Communication Engineers (IEICE) of Japan.