To provide a human body sensor including a radio sensor detecting a presence of human body by transmitting and receiving of radio wave, which never causes miss-sensing of human body in case that a water droplet falls over a radio emitting surface due to dew condensation or the like.
This human body sensor comprises a transmitting part transmitting radio wave, a receiving part receiving reflected wave, and a mixer part extracting an output signal of low frequency from a transmitting signal and a receiving signal, in which the presence of human body is sensed depending on the amplitude and duration of the output signal. In this sensor, a first output level larger than 0-level is set for comparing an output level that is the amplitude value of the output signal, and when the output signal is the first outlet level or more, and the output signal in a predetermined time before then is smaller than a noise level, it is not determined as the presence of human body.
FURUTA YUICHI
TSUJITA MASAMI
