Patent ID: 7626498

Claim:
A sensor node having a radio-communication circuit and a sensor, for transmitting data obtained by the sensor by radio communication, comprising: a chip-type dielectric antenna which is connected to the radio-communication circuit; a first board which has a first surface on which the antenna is placed and a second surface opposed to the first surface; a case for containing the first board; and a band attached to the case to fix the case to a skin of a human wrist, wherein a power supply layer and a ground layer are provided in the first board, wherein the case is fixed to the skin by the band to position the second surface closer than the first surface to the skin and the antenna in an upper portion of the case in a 12 o'clock direction of a wristwatch when placed on the human wrist, and wherein an area surrounding the antenna is set on the first board and no conductive plane is provided in the power supply layer and the ground layer inside the area.