Small and high-performance antennas are needed for mobile communication systems, such as a cellular phones and a personal handy phones, because portable radio equipment has become extremely small in recent years. However, it is difficult to design the antennas because of the effects of a human body and the portable equipment. In this study, characteristics of antennas mounted on the portable equipment near a human body are analyzed using the FD-TD method in order to clear effects of a human body on the antennas. An analysis model is composed of a human body model and the antenna mounted on a conducting box. It is confirmed from a comparison between calculated and measured results that the model is useful to analyze the characteristics of antennas and the effects of human body on the antennas can be well examined with it. Using this model, characteristics of a λ /4 monopole antenna and a planar inverted-F antenna in a frequency range of 600-1900MHz are calculated. The calculated results indicate that radiation efficiency becomes lower than 45% owing to the effects of human body model. Moreover, it becomes clear that the effects of the human body model on two types of antennas differs with each other.
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