Traffic radar uses Doppler radar to detect the speed of vehicles. It works by emitting a constant microwave beam down the road. When the beam bounces off a vehicle, the radar antenna detects the reflection and uses the Doppler principle to calculate the vehicle's speed based on the difference between the transmitted and reflected frequencies. Traffic radar is small enough to fit in a police cruiser and does not require a sweeping beam or radar screen like other types of radar. It was developed in the 1940s for military use and was first adopted by police in the late 1940s to issue speeding tickets.

1. ‫الرحيم‬‫الرحمن‬‫هللا‬‫بسم‬

2. Introduction:
 There are many kinds of radar:
Military radar, weather radar, and
air-traffic control radar.
 Traffic radar is quite different and falls
into its own category.
 Traffic radar, by contrast, is very simple.
• It must be simple because it can be no
larger than what will fit on the dashboard of
a mid-size cruiser.

3. History:
1947 radar gun was
developed for military
during world war 2.
1948 starting by police to
issue speeding records.
That was used in garden
--city & new york.
Christian Doppler who
proposed Doppler
principle in 1842 .

4. How Traffic Radar Works:
 Traffic radar does not sweep:
 The area under surveillance by traffic
radar is quite limited.
 Traffic radar does not use a modulated
beam.
 It uses a constant beam.
 Traffic radar does not have a radar screen.

5. Traffic Radar “The Basic Idea”:
 Traffic radar's constant beam acts very
much like a searchlight, They travel in
straight lines and they are easily
reflected. Metallic objects like cars…etc
 Traffic radar works by shining its
microwave searchlight down the road.
 When you come in range, the beam
bounces off your car, and the radar
antenna looks for the reflections.
 Radar range depends upon two things:
power of the radar and reflectivity of the
target.

6. How Traffic Radar Measures Your
Speed:
 It uses a phenomenon of physics know as
the Doppler principle.
 Doppler principle works with sound waves.
The classic example is heard along railroad
tracks. As the train approaches, you hear
the sound at a fixed pitch.
 It compares the shifted frequency of the
reflection to the original frequency of the
beam it sent out and from the difference it
calculates speed, which it then displays on
its digital readout. That's all there is to
traffic radar.