4. INTRODUCTION
RADAR -- Radio Detection and Ranging
Radio– Radio waves are used
Detection-- To identify the target
Ranging– To find the distance or position of the
target
Founder – First practical radar
-- British Physicist Sir Robert Watson
Watt in 1935
Father of Radar – Heinrich Hertz -- German
Physicist
5. Basic Principle
The electronic principle on which radar
operates is very similar to the principle of
sound-wave reflection.
If you shout in the direction of a sound-
reflecting object (like a rocky canyon or cave),
you will hear an echo.
If you know the speed of sound in air, you can
then estimate the distance and general
direction of the object
8. IMPORTANT TERMS
Range
Pulse Repetition Frequency
Maximum Unambiguous Range
Minimum Range
Clutters
9. Range
The distance between Radar and target is called
Range of the target or simply range, R
Speed = Distance /Time
Distance = Speed × Time
2R = c × T
R = c × T/2
10. Pulse Repetition Frequency
The time interval between the successive clock
pulses is called pulse repetition time, TP .The
reciprocal of pulse repetition time is called pulse
repetition frequency, fP
Mathematically, it can be represented as
fP = 1/Tp
11. Maximum Unambiguous Range
we have to select the duration between the two
clock pulses in such a way that the echo signal
corresponding to present clock pulse will be
received before the next clock pulse starts. Then,
we will get the true range of the target and it is
also called maximum unambiguous range of the
target or simply, maximum unambiguous range.
Run =
12. Minimum Range
We will get the minimum range of the target,
when we consider the time required for the echo
signal to receive at Radar after the signal being
transmitted from the Radar as pulse width. It is
also called the shortest range of the target.
Rmin =c τ/ 2
13. Clutters – Unwanted echoes
- unwanted received signals
21. DOPPLER EFFECT
If the target is not stationary, then there will be a
change in the frequency of the signal that is
transmitted from the Radar and that is received
by the Radar. This effect is known as the Doppler
effect.
According to the Doppler effect, we will get the
following two possible cases −
The frequency of the received signal will
increase, when the target moves towards the
direction of the Radar.
The frequency of the received signal will
decrease, when the target moves away from the
Radar.
22. fd = 2 vr / λ
fd = Doppler frequency shift
vr = Velocity of the target
λ = Wave length
23. ft --- Transmitted wave frequency
( ft - fd )-- Received wave frequency if the target
is moving away from radar
( ft + fd )-- Received wave frequency if the target
is approaching towards radar
26. WEATHER RADAR
The Doppler radar used in weather forecasting
measures the direction and speed, or velocity, of
objects such as drops of precipitation. This is
called the Doppler Effect and is used to
determine whether movement in the atmosphere
is horizontally toward or away from the radar,
which aides in weather forecasting.
29. POLICE RADAR
Police RADAR.
RADAR speed detectors bounce microwave
radiation off of moving vehicles and detect the
reflected waves. These waves are shifted in
frequency by the Doppler effect, and the beat
frequency between the directed and reflected
waves provides a measure of the vehicle speed.
31. FUTURE RADARS
TV Signals Can be Used in Radar Capacity: TV signals’ behavior is
similar to radar, but they operate at different ends of the radio spectrum.
New technology has emerged using receivers tailored to these signals,
and successfully tracked 30 airplanes at a range of 10,000 feet.
And where some radar can confuse wind turbine activity with aircraft,the
TV signals encountered much less interference. TV signal “radar” takes
advantage of broadcast networks that already disseminate the signals.
Using TV signals could mean a radar-like technology that is more cost-
effective than traditional radar to develop and use.
PASSIVE RADAR IN DEVELOPMENT, EXPECTED TO BE A GAME
CHANGER
Passive radar, a different type of radar technology, is set to be the next
big thing in military radar applications. It operates almost in reverse to
existing radar—while radar puts out electromagnetic signals to function,
passive radar takes in existing electromagnetic signals from the
atmosphere to support imaging and tracking capabilities. Passive radar
is less expensive to operate and is more covert than traditional radar.
The global passive radar market is expected to hit $10 Billion USD in
annual spending by 2023.
32. 3D radar provides for radar coverage in three
dimensions; unlike the more common 2D radar
which provides range and bearing, the 3D radar
also provides elevation. Applications include
weather monitoring, air defense, and surveillance.
