Compact magnetic field enhanced antennas for portable personal wireless device applications.

摘要

The development of electrically small antennas is integral to maintaining the performance of today's smaller personal communication devices. A new antenna for portable wireless device applications is investigated. The Transverse Bilateral Helical (TBH) Antenna provides relatively wide bandwidth and high efficiency in a compact structure. The antenna's resonant frequency exhibits low sensitivity to placement on the human body.;A survey of recent developments in small antenna design is conducted to provide insight into current developments and techniques. The properties of the normal mode helix, cylindrical dipole, and small loop antennas are discussed. Theoretical limits of the minimum Q and maximum gain of small antennas are reviewed to provide a bound on the expectations of small antenna designs. Elements of the antenna designs presented in the survey are combined to form the Transverse Bilateral Helical antenna and provide the theory of its operation. A repeatable antenna fabrication method is then discussed. Antenna design and analysis is aided through the use of Finite Element techniques. The High Frequency Structure Simulator (HFSS) from Ansoft is utilized for simulating antennas and surrounding structures.;When small antennas are placed next to a human body, significant changes in radiation performance are often observed. Key consideration is given to simulation of antennas near the human body, with the aim of minimizing the effects of body placement on antenna performance. Tissue properties and dimensions of biological phantom models are presented. The effect of radio frequency energy on biological tissue is an increasing area of research. These effects are quantified in the measurement of specific absorption rate (SAR). Simulations using biological phantoms are conducted to compare the SAR performance of the Transverse Bilateral Helical antenna to other popular small antennas. Accuracy of each simulation model is determined through the physical construction of several antenna designs. The antennas are then analyzed in typical portable wireless device applications.