Home' RTCA Documents for Review : DO-230H FRAC Contents 154
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The range cut-off is between 30 and 122 meters (100 to 400 feet).
System Limitation –
The mono-static microwave is subject to the same potential problems as other micro-wave systems.
Be aware of large fixed objects reflecting microwave energy such a fence panels.
Moving objects in the area such as vehicles can affect the detection pattern.
Provide good drainage for areas under the detection zone.
Avoid sharp drop off and ditches under the detection zone.
Grass and vegetation must be kept cut under the detection pattern to a max of 3 inches.
The testing conducted is the same as for the Bi-Static Microwave.
A microwave perimeter detection system should be capable of detecting an intruder weighing a
minimum of 35 kilograms (77 pounds) passing through the zone of detection between the
transmitter and receiver, including the area in front of both the transmitter and receiver, whether
the individual is walking, running, jumping, crawling, or rolling.
Provision should be made to ensure detection in spite of the dead spots in front of transmitters and
receivers. The beam should be modulated and the receiver should be limited to respond to selected
frequencies to decrease susceptibility to “receiver capture.”
Three tests are performed to test the performance of the system:
o Post-Climb-and-Jump test to determine if an intruder will be detected when climbing the
microwave pole and attempting to jump over the beam.
o Crawl test is performed at 10 feet intervals in a sector at a crawl speed of 4 to 6 inches per
o Run-and-Jump test is performed at 20 feet intervals from the length of the sector to verify
that an intruder cannot jump over the detection beam without being detected.
Electric Field or Capacitance
General Characteristics – An electric field or capacitance perimeter intrusion detection system is considered
terrain-following if the grade is uniform between mounting supports. Electric Field systems are volumetric
in nature and the intruder only has to enter the space, and does not have to actually physically disturb the
fence, for the alarm to be triggered. A typical system consists of field wires, a field generator, sensing wires,
a sensing filter, an amplifier, a discrimination unit, and an output for connection to an annunciation device.
An electric field sensor can be free-standing or mounted to an existing fence. Electric field systems range
from 4 to 7 wire systems, i.e., 2 sensing and 2 field wires up to 3 sensing and 4 field wires.
A person approaching the system changes the pattern of the electric field.
Sensing wires installed at different locations within the transmitted pattern detect changes occurring
in the pattern. If the changes are within the frequency bandpass of objects comparable to an
individual’s movement, a detection signal is generated.
Some systems have additional signal processing to discriminate between people and what would
otherwise be nuisance alarms (e.g. small animals or rodents.)
Electric field systems should be installed with zones that are limited to 100 meters (328 feet) or
less in order to have effective detection sensitivity for assessment and response.
System Limitation –
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