Development Of A New Photoelectric Security Alarming System

The safety-defending techniques are involved in most aspects of the society and they are very important in protecting the benefit and security of the people and the country. Based on the pyroelectric infrared—microwave double detecting technique, this paper designed a new photoelectric security alarming system. Double detecting technology integrates the two detecting technology, with the relation of "together" to trigger the alarming system. The infrared radiation (human body temperature) of intruders was sensed by the Pyroelectric infrared sensor and then was changed into ultra low frequency signals. The signals were amplified by the circuit and then been output. At the same time, the frequency (or phase) of echo signals which the microwave detector received was changed. The changes transformed into electric signals and then output after the circuit processing. After judging the two groups of signals which reached the logic product gate at the same time, the circuit launched alarm signal through the antenna. The alarm signals can be received by the accepting circuit or the radio.The results of the photoelectric security alarming system were measured by experiments, they are: probing range is not smaller than 10m,the microwave centre frequency is f₀ = 2000 MHz, this system can stand inthe range of 25¹000MHz frequency disturbance, and can withstand 100W interfering signals in the distance of 3m. The system can be widely used in the important departments of society, such as military installation, national power system, communication system, warehouses, and in all kinds of banks, etc.