Installation Guide

AIMS Fast-Scan Radar v3.22 Installation and Operations Manual
DMT, LLC • DMT-M200-311 • 08/2009
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detection range will be less than the maximum rated performance. So for our example, a
crawling human will be detected at ranges less than 1.5 km for a 1.5 km radar.
If the person is walking behind a building or wall, the radar will not detect that object. In
addition, a person partially obstructed will have a lower RCS and will also be detected at shorter
ranges than a walking human. An example of this is thick vegetation. If a person walks in
thick brush up to his/her waist, then the maximum detection range for this person is likely to be
reduced to 75 to 80% of the range of a fully illuminated person.
There are 4 methods, however, for increasing the detection range of the radar:
- Increasing the GAIN setting of the radar;
- Decreasing the SENSITIVITY setting of the radar;
- Increasing the DOP RESOLUTION setting of the radar;
- Slowing the spin rate of the radar.
With the exception of the spin rate, these controls are all found on the Radar Tab.
Increasing Gain actually increases the transmitted pulsewidth of the radar. The greater the
pulsewidth, the greater the average power output of the radar. This, in turn, will increase the
detection range against all intruders.
Decreasing the Sensitivity setting actually lowers the threshold of the radar. Lowering the
threshold of the radar will permit the weaker signals from distance objects to be detected at
further ranges. However, lowering the Sensitivity control too low will cause more false alarms
from near-in objects.
Increasing the Dop Resolution control value actually increases the number of pulses integrated
by the radar. The more integrated pulses, the greater the effective signal strength for coherent
objects (like people and cars). The greater the effective signal strength, the longer the detection
range. Unfortunately, the price is paid by longer processing times. This often translates to
slower spin rates.
Slowing the spin rate of the radar enables more energy to return to the radar receiver from the
“sweet spot” of the antenna. The “sweet spot” (or inner 1-dB of the antenna’s main lobe)
supplies the greatest amount of available power on the object of interest. There is a point of
diminishing returns. Spinning the radar too slow will provide no additional performance boosts
and can cause the radar to miss seeing an intruder due to the low revisit rate. Currently, the spin
rate can only be set on the radar server code.
6.5 How do I use Sensitivity and Gain?
The Sensitivity control on the Radar Tab is a measure of the required signal strength needed to
declare an alarm. The AIMS radar calculates the average signal strength using the outer cell
slices of the Doppler Spectrum for every range bin. This value plus the Sensitivity setting value
is compared to the peak Doppler response for every range bin. This procedure reduces false
alarms by ensuring that the threshold is applied consistently above the average signal for every
range bin. Figure illustrates the point. The red curve is the average Doppler spectra level versus
range. The blue curve adds the threshold (Sensitivity) value to the red curve. It is this blue