The method of auxiliary sources applied to the analysis of adaptive transverse resonant antennas

Abstract

The beam-steering capability of compact antennas presenting transverse resonances could be employed in wireless applications. Adaptive beam-steering arrays can improve communication reliability and energy efficiency. The 2-D Method of Auxiliary Sources is employed to study the performance of a compact size transverse resonant antenna composed of wire radiators embedded in a dielectric substrate and backed by a conductive surface. In this particular case, the antenna is capable of scanning and changing the width of the main lobe of its pattern, as well as reduce the back radiated energy. Attention is paid to energy absorption by the user$ body, as well as to EMC issues with body-worn electronic devices. Problem StatementMany of the existing antennas employed in wireless communications do not satisfy requirements of coverage and efficiency dictated by the modem wireless communications applications. For instance, the quasi-omnidirectional azimuth pattern of cellular phone antennas tend to satisfy the requirements in terms of coverage, but at the same time produces a drastic reduction in efficiency due to the close proximity of the userS head. The strength of the electromagnetic field near the antenna relatively high, comprising both reactive and radiated components. In this case, there is no use in radiating RF power in all directions, when the connection of the phone with the base station is established [l]. The directional radiation is enough for cominunication purposes, and would improve energy efficiency.In this work, we considered an antenna formed by an array of three wire radiators embedded in a substrate layer backed by a reflecting surface. The radiation beam of such directive antenna can be steered by appropriate current amplitude/phase combinations of the radiating elements. The investigation of the radiation parameters of the present antenna has been canied out using the Method of Auxiliary Sources (MAS) [2], in its 2-D formulation, applied to the structure depicted in fig. 1. It was shown that the MAS is an efficient tool for the investigation of such kind of problems.Because of strong electromagnetic interaction between the antenna and the user and the variable distance between them, it is impossible to obtain a good matching of the antenna for all operating positions. The back plane would provide a certain degree of decoupling between the antenna and the body and improve energy efficiency. The directional beam of the antenna and the steering capability would enhance a reliable connection with the base station in a typical scattering environment.