1. PRESENTATION ON CW DOPPLER RADAR
Prepared by,
Anurag poojari
Abhijit Pujari
Harshad Rane
Chirag Rangrass
Mandar Rane

2. Presentation Outline INTRODUCTION PRINCIPLE WORKING ADVANTAGES
DISADVANTAGES
APPLICATION
CONCLUSION

3. INTRODUCTION
Basically radar are the means of gathering information about distinct objects ,or targets,by sending electromagnetic waves at them and analyzing the echoes.
In cw doppler radar consists of a transmitter and a receiver,each connected to directional antenna.
The transmitter is capable of sending
out a large UHF of microwave power through
The antenna.The receiver collects as much
energy as possible from the echoes
in its direction by the target.
cw doppler radar sends out continuous
sine waves rather than pulses.
Cw doppler radar

4. PRINCIPLE
cw doppler radar uses the doppler effect to detect the frequency change caused by a moving target,and displays this as a relative velocity.
Continuous-wave radar system is a radar system where a known stable frequency continuous wave radio energy is transmitted and then received from any reflecting objects. The return frequencies are shifted away from the transmitted frequency based on the Doppler effect if they are moving.
The Doppler effect (or Doppler shift), named after Austrian physicist Christian Doppler who proposed it in 1842, is the change in frequency and of a wave for an observer moving relative to the source of the waves. It is commonly heard when a vehicle sounding a siren approaches, passes and recedes from an observer. The received frequency is increased (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is decreased during the recession.
Doppler Shift: A frequency shift that occurs in electromagnetic
waves due to the motion of scatterers toward or away from the observer.

5. Sign conventions
The Doppler frequency is negative (lower frequency, red shift) for objects receding from the radar
The Doppler frequency is positive (higher frequency, blue shift) for objects approaching the radar
Red: Receding from radar
Blue: Toward radar

6. WORKING The transmitter output is mixed with the outputft CW
TRANSMITTER
OSCILLATOR
The transmitter output
is mixed with the output
of the local oscillator
and the sum is fed to
the receiver mixer.
This also recieves
recieves the doppler
shifted signal from its antena,
and produces output difference frequency
that is typically 30Mhz,plus or minus the
doppler frequency.The output of this mixer is
amplified and demodulated again and the
signal from the second
detector is just the doppler frequency ft fi
TRANSMITTER
MIXER IF
OSCILLATOR
ft +fI
RECEIVER
FIXER IF
AMPLIFIER
DETECTOR
ft ±fd
AUDIO
AMPLIFIER
ft ±fd fd

7. ADVANTAGES Capable of giving accurate measurements . Simple circuitry.
Small size compared to other radar.
Can measure direction of target ,
in addition to its velocity .

8. DISADVANATGES transmits.
Its is limited in the maximum power its
transmits.
It is incapable of indicating the range of the
target, it can only measure its velocity.
Can not detect moving target easily.
Can not measure range

9. APPLICATION Used in air craft navigation for speed measurements
Doppler radars are used in air defense, air
traffic control sounding satellites, police
speed guns and radiology.

10. CONCLUSION
Cw Doppler radar is a simple radar which uses the Doppler effect to detect the frequency change caused by a moving target ,& displays this as a relative velocity.

11. COMMUNICATION SYSTEMS
REFRENCES
COMMUNICATION SYSTEMS
GEORGE KENNEDY

12. THANK YOU