Design of mobile antennas and effects of handset case, battery and human head on the antenna performance

Abstract

Aesthetical design and marketing aspects have a large impact on the development of mobile phone. Therefore there is a remarkable trend to fully integrate the antenna in the mobile phone. Compared to traditional antennas it is more complicated to master the typical parameters like bandwidth, radiation pattern, and radiation gain of the antenna within the limited antenna volume. Besides, the influence of the user and handset parameters like the housing, LCD, keypad, and battery on the antenna performance causes the design procedure of antenna to be more complicated. This becomes even more critical with respect to multiband functionality which is an essential feature of modem mobile phone. To enable a rapid and efficient design some general relations concerning the physical behavior of an antenna in a small mobile have to be considered. This thesis focuses on the two most important issues in internal and external antennas for multiband operation of mobile handsets: the design technique of small broadband antenna and investigation of the housing, battery, and human head effect on the antenna performance. A broadband external antenna with tuning patch which facilitates the adjustment of the resonant frequencies and leads to a large bandwidth design is proposed, and for internal type the idea which enables the proposed antenna to operate at multiple bands is presented. Each of these antennas with compact size is built in mobile phone with battery, and by applying to head phantom the variation of the antenna characteristic due to those parameters is investigated. First of all, a triple-band stubby antenna fed by coaxial probe and the tuning technique are proposed for operating at PCS, IMT-2000, and Bluetooth bands. The proposed antenna shielded by the antenna cover consists of the two radiating elements. The impedance matching and bandwidth for the proposed antenna are mainly affected by the length of the ground patch at the bottom of small substrate. By properly ...