Decatur Electronics GENESIS-II DIRECTIONAL, User And Installation Manual

Page: 44 / 90

GENESIS-II DIRECTIONAL ™ USER’S AND INSTALLATION MANUAL
44
Rev. 02/05
8. Performance Tips
Understanding potential radar interference and what to do
when it occurs can greatly increase the radar’s performance.
8.1 How Radar Works
Determining a vehicle’s speed, begins with the radar
antenna transmitting and directing a beam of
microwave energy (radio waves) at an approaching (or
receding) target vehicle. When energy from this beam
strikes a moving 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.
8.2 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 8.2.2 through 8.2.10.
• The Doppler tone is corrupted with noise.
• Speeds are irregular and do not provide a valid
• Erroneous speeds appear to track with the
engine speeds.