Radiation and ohmic resistances in very small meander line antennas of less than 0.1 wavelength

Abstract

AbstractDemands for extremely small antennas to be used in radiofrequency identification tags for ubiquitous communication have increased. Examples of very small antennas utilizing meander line structures are seen. To date, important studies have been carried out on basic design and on improvement of the radiation efficiency by a folded configuration. Most of the structures studied have dimensions of more than 0.1 wavelength. For the demands of ultracompact antennas, this paper deals with meander line antennas whose dimensions are less than 0.1 wavelength. First, the parameters for resonant configurations are derived for antennas with dimensions of 0.1 to 0.025 wavelength. Next, the radiation resistance and the ohmic resistance are studied in the folded structures. First, through a transmission line model analysis, it is shown that the step‐up ratios of radiation and ohmic resistances in the case of folded structures are different. In addition, these resistances that are basic values of electrical performances are derived through electromagnetic simulations. Further, in order to confirm the validity of the numerical results and the realizable performance, antennas with dimensions of 0.1 and 0.05 wavelength were fabricated. Electrical characteristics are compared, and good agreements are found. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(8): 1–11, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20204