A mobile antenna study of radiation efficiency in human head and hand environment

Modern wireless devices such as mobile phones have been made more compact and low profile, which drives usage of internal antennas. But radiation performance of an internal antenna often degrades a lot when the human body, such as a head and a hand are positioned against the device. In this paper, internal antenna topologies for mobile phones are discussed. Specifically, a candy bar (PDA) type of phone model is used to carry out the study. The bands to be covered are CELL band (824 MHz - 894 MHz) and PCS band (1850 MHz - 1990 MHz). In this study, the radiation performance of a single dual band antenna approach and a combination of two separate single band antennas are compared. The separate antenna topology has demonstrated better antenna efficiency in human head and hand environment. In addition, a parasitic resonator is added to improve the hand grip performance of the PCS band PIFA. Discussion has been made in the end on when this topology can be used and the tradeoff of using this resonator in an active phone.