Antenna for portable radio device

摘要

A finger-ring-type radio device is worn by a person to wirelessly transmit his physical data such as blood pressure or pulsation. The radio device is composed of a finger ring having a slot antenna as a magnetic-field-mode antenna and a flat plate having a patterned antenna as an electric-field-mode antenna. A transmission circuit for generating high frequency signals representing the physical data is also mounted on the flat plate. Both antennas having respective characteristics and radiation directivities are combined to form a composite antenna from which the high frequency signals are radiated. The radiation efficiency of the composite antenna is improved by combining both antennas. The slot length of the slot antenna is extended by forming it in a zigzag shape, so that the slot length properly corresponds to the high frequency to be radiated and the antenna efficiency is improved. A ground surface of the transmission circuit mounted on the flat plate may be utilized as the electric-field-mode antenna in place of the patterned antenna by coupling the ground surface with an electric-field-mode component included in the slot antenna.