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

Presentation Outline INTRODUCTION PRINCIPLE WORKING ADVANTAGES DISADVANTAGES APPLICATION CONCLUSION

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

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.

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

WORKING The transmitter output is mixed with the output 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 TRANSMITTER MIXER IF OSCILLATOR ft +fI RECEIVER FIXER IF AMPLIFIER DETECTOR ft ±fd AUDIO AMPLIFIER ft ±fd fd

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

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

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.

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.

COMMUNICATION SYSTEMS REFRENCES COMMUNICATION SYSTEMS GEORGE KENNEDY www.answer.com

THANK YOU