PURPOSE: To prevent an ultrasonic body detector from malfunctioning against a noise which varies in repetition period and continuance in a short time by providing a signal processing circuit which estimates variation in the repetition period and continuance of a periodic noise from a received signal pattern stored in a storage circuit and sending an ultrasonic wave in a period wherein the signal processing circuit estimates that no noise is present and body detection is possible.
CONSTITUTION: This body detector is provided with the storage circuit 4 for storing plural noises outputted by a receiving circuit 3, a comparing circuit 5 which compares the previously stored noises with a current noise to detect variation in the repetition period or continuation of the noise, and the signal processing circuit 6 which reads the variation in the repetition period or continuance of the noise from the output of the comparing circuit 5 to estimate the reception time point and continuation of the noise. The signal processing circuit 6 has a function core estimating the arrival time point and continuance of a noise expected to arrive next and estimates the period wherein there is no noise present and the body detection is possible. This signal processing circuit 6, therefore, drives a sending circuit 2 in the period wherein the circuit estimates that no noise is present and the body detection is possible, thereby sending ultrasonic wave pulses.
KATAYAMA SUSUMU
AZUMA NAOYA
YAMANE TOSHIKI
| JPS60127482A | 1985-07-08 |