GENESIS-VPD™ USER’S MANUAL
24
Rev. 09/04
5. Performance Tips
Understanding potential radar interference and what to do
when it occurs can greatly increase the radar’s performance.
5.1 How Radar Works
Determining a vehicle’s speed, begins with the radar
gun transmitting and directing a beam of microwave
energy (radio waves) at an approaching (or departing)
target vehicle. When energy from this beam strikes a
vehicle, a small amount of the beam is reflected back to
the antenna. The reflected signal frequency shifts by
an amount proportional to the speed of the target
vehicle. This is known as the Doppler effect. The radar
device then determines the target vehicle speed from
the difference in frequency between the reflected and
transmitted signal.
5.2 Interference Sources and Remedies
When properly deployed and operated, Doppler radar
technology is extremely accurate and reliable.
However, variations in the environment can cause
situations and circumstances, which can cause
spurious (erratic and unusually low or high) speeds to
display. Signs that a speed is spurious can include the
following characteristics:
•
A reading appears when no target vehicle is in
the operational range of the antenna.
•
A target vehicle entering the operational
range overrides the interference signal,
causing the display speed to change
suddenly to the vehicle’s speed. This
comment applies to paragraphs 5.2.2
through 5.2.8.
•
The Doppler tone is corrupted with noise.
•
Speeds are irregular and do not provide a
valid traffic history.