This post introduces us to one of the most
major and important device of the defense systems “RADAR”.
INTRODUCTION
Radar stands for radio detection and ranging systems.
These are devices or instruments which are used to detect the speed, range and
even the speed of the bodies. Radar transmits electromagnetic signals in air at
different wavelengths and its receiver listens for the reflected echoes that
are when the transmitted signal contacts with an object, the object reflects
the signal and the receiver of the radar listens for this reflected signal from
which it determines the speed and distance of the object.
The signal from the radar travels with the speed of
light= 3 x 108 m/sec. The radar calculates the time taken from the
instant the signal is transmitted and the time signal received and then there
is just a simple primary concept of distance= speed x time, and the distance of
the target object is calculated.
HISTORY OF RADAR
The radar has its historical importance, invented and
developed by Germany and England. It has great role to let the English win over
the Germans. The English with the help of radars detected the coming of German
aircrafts much earlier and get prepare themselves for a response attack and
even to bring down German stukas.
APPLICATIONS OF RADAR
Radar has various applications including
·
Aircraft altimeters which are used to detect
the distance of the flight from the ground
·
Whether forecasting as radars can be used to
detect the position of the clouds
·
Traffic control on roads by detecting speed
of high speed moving vehicles
·
Military purposes as they are used to detect
enemy ships and aircrafts. Also radars are used as missile guidance radars
Components of radar
Radar consists of following components:-
Transmitter: -
It creates the radio wave to be sent and modulates it, amplifies it and
transmits it at a certain high power. Various microwave devices such as
klystron, magnetron, TWT are used to generate these waves.
Receiver: - It is a very sensitive device especially
to high frequencies, it receives the signal and amplifies the weak reflected
signal.
Antenna: -
the antenna takes the radar from transmitter and puts it into air and
similarly gets the reflected signal from
air to receiver.
Duplexer: -
this is a switching device which alternately connects to transmitter and
receiver. Its purpose is to protect receiver from high power of the
transmitter.
Synchronizer:- it
coordinates the timing for range determination. it regulates the rate at which
pulses are sent
Power supply:-
it provides electrical power for all the components. The largest consumer of
power is transmitter.
Display: -
The display unit shows the various form of signals received for the operator to
understand them examples are PPI, RHI, FPD etc.
TYPES OF RADAR
Radar is generally categorized into two types according
to the type of signal they transmit.
1) Pulse
wave radar: - it transmits pulses of signals with a certain time
interval between two pulses.
2) Continuous
wave radar: - it transmits a continuous wave and looks for change
in frequency. These radars function on the principle of Doppler Effect.
Doppler Effect in detail
In our everyday life we have multiple examples of Doppler
Effect; the whistle from a moving train is an example. As a train approaches a
stationary listener , the pitch of the whistle sound gets higher and as the
train passes the stationary listener the sound of the train whistle gets
decreasing.
Scientifically, if either source of oscillation or
observer of oscillation is in motion an apparent shift in frequency takes
place.
Practical radars
The above explained till now is simply the basic radar.
But practically radars have to deal with a lot of noise. It could be noise in
the receiver possibly due to various microwave components or clutters which is
the noise generated by natural environment.
Radar below sea level
Radars cannot work underwater as radar transmits electromagnetic pulses which get attenuated or short in water as sea water is saline and a good conductor of electricity.
Hence sonars are used which instead of electromagnetic
waves uses sound waves.
A discussion on Radars in daily use is here on how RADARS are present in our cars see:-driving with RADARS
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