Use of a time-variation ultrasonic signal and PIR sensors to enhance the sensing reliability of an embedded surveillance system

In this paper we design and implement an embedded surveillance system by use of a time-variation ultrasonic coding signal with multiple pyroelectric infrared sensors (PIR) to detect an intruder in a home or a storehouse. The ultrasonic sensor module consists of a transmitter and a receiver which are placed in a line direction; however, ultrasonic sensors with the same frequency are subject to interference by crosstalk with each other and have a high miss rate. To overcome these disadvantages of the ultrasonic sensor, we propose a coding mechanism to reduce both crosstalk and environmental interference and to enhance the distinguishing features of the signal. In addition we use a time-variation coding signal to make the system more reliable against the breaking of the system when the coding signals vary. Both ultrasonic sensors and PIR sensors are managed by the majority voting mechanism (MVM).