Pan Pacific Symposium Conference Proceedings


Authors: A. Gandelli, D. Monopoli, A. Pirisi and R. E. Zich
Company: Politecnico di Milano, Dipartimento di Elettrotecnica
Date Published: 1/24/2008   Conference: Pan Pacific Symposium

Abstract: With the advancement of wireless communication systems, low cost, minimal weight, compact and low profile antennas are in great demand for both commercial and military applications. Furthermore, as the size of wireless hand-held devices shrinks, it is desirable to integrate the antenna directly on the chip package to cut down cost and provide flexible integration. Conformal low-profile antennas, such as printed dipoles, rectangular patches and slots, are widely used in large arrays on ground based, vehicular, air-borne and shipboard applications. Microstrip patches are usually used as radiating elements also in arrays and planar reflector antennas. These traditional resonant structures are typically half a wavelength in the critical dimensions and have relatively narrow bandwidth. In order to overcome these limitations, circular and annular shaped microstrip elements can be used, where the resonant dimension is related to half the circumference. This leads to a more compact solution, since for the same frequency the size of the patch is smaller. Another advantage of this solution is the possibility of working with double polarization. This paper investigates the performances of microstrip elements with circular annular shapes and suitable additional geometrical features, such as slots, to control the resonance behavior. Especially, a study of efficiency of the antenna has been done. The idea is to use a ring of EBG (electromagnetic band gap) material in order to reduce the surface wave and therefore to increase the antenna efficiency in terms of both received and radiated power by the whole antenna.

The analysis process is done in three steps. First, we characterized the patch in term of an equivalent circuit model. Then we investigated the mutual coupling of an array of patches. Finally we developed a suitable EBG ring in order to increase the efficiency of the antenna. The last operation is important for the optimization and design process.

Keywords: Wireless Sensor Network, Annular Antenna, Phase Control, Reflect array

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