PRESENTATION ON CW DOPPLER RADAR

1. PRESENTATION ONCW 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. 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. PRINCIPLE

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 ft 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 IF OSCILLATOR TRANSMITTER MIXER 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 • 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. REFRENCES COMMUNICATION SYSTEMS GEORGE KENNEDY www.answer.com

12. THANK YOU