Anti-theft system with perimeter protection environment: the microwave barriers

The active barrier microwave detector is one of the most 'safe and reliable use in perimeter protection for outdoor use. A barrier is formed by a transmitter device and a receiver device. The transmitter emits an electromagnetic radiation whose frequency is around 10 GHz, which is directed, by means of an 'antenna, towards the receiver device. The receiver, too 'it with its antenna can be placed from a few meters up to 250 meters away. The microwave beam that is established between the transmitter and the receiver, when there are no obstacles in the middle, allows to obtain in output of the analysis circuit of the receiver, a signal level proportional to the 'amplitude of the received signal.


This condition is interpreted by the control unit as a condition of rest. An intruder who attempts to cross this beam, produces a perturbation that is interpreted by the receiver as a change in amplitude of the received signal.


This variation is analyzed by the receiver circuit and subsequently processed to determine whether or not the notification of an alarm condition. A very important factor for the successful operation of a microwave barrier is that the signal level is kept constant in time. Upon the occurrence of a disturbance in the 'operating environment of the barrier (fog, rain, hail), the signal level may gradually decline. The analysis circuit of the receiver device is responsible to bring the received signal level to the level of a rest condition. The sudden variations of the received signal, with respect to this condition of rest, determine the produce of an alarm message by the receiver. The microwave barriers are used to protect the external perimeter, boundary walls and gardens. It 'a type of detector is very difficult to sabotage and has a low susceptibility to false alarms, which is why this type of protection is often used in high-risk applications.





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