| Summary: | 碩士 === 輔仁大學 === 電機工程學系碩士班 === 102 === In this thesis 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 not only are subject to interference by crosstalk with each other but also 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 an ideal case, the reliability of time-variation coding signal consists of bit rate, coding efficiency and error bit rate. To confirm the sensing probability of a coding signal, we find the relationship between a signal interferes with timing and reliability when an intruder passes through the detection area. In addition we use a time-variation coding signal both to make the system more reliable and to prevent of the system from crashing when the coding signals vary. Both ultrasonic sensors and PIR sensors are managed by the majority voting mechanism (MVM).
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