Doppler Radar

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Information about Doppler Radar

Published on August 23, 2007

Author: anilachuthan


DOPPLER RADAR:  DOPPLER RADAR Anilkumar Achuthan Computer Science Department Southern University Outline:  Outline Introduction about Doppler effect. Quantitative analysis. Doppler effect as a forecasting tool. Concepts of radar gun. Cosine effect. Conclusion. Introduction:  Introduction Doppler Effect A change in the observed frequency of a wave, as of sound or light, occurring when the source and observer are in motion relative to each other, with the frequency increasing when the source and observer approach each other and decreasing when they move apart. Real Shift Apparent Shift The Doppler Effect:  The Doppler Effect Just as common a natural phenomena as echo. Occurs when sound is generated by or reflected off of a moving object. In the extreme, Doppler shift creates sonic booms! Visual Representation:  Visual Representation Quantitative Analysis:  Quantitative Analysis For waves that travel through a medium (sound, ultrasound, etc.) the relationship between observed frequency f’ and emitted frequency f is given by: Where v is the speed of waves in the medium and vS is the velocity of the source. Doppler radar as a forecasting tool:  Doppler radar as a forecasting tool Slide8:  The computer that's a part of a Doppler radar uses the frequency changes to show directions and speeds of the winds blowing around the raindrops, insects and other objects that reflected the radio waves. A Typical Radar Gun:  A Typical Radar Gun Consists of a microwave transmitter, an antenna, a receiver, and timing and control circuitry Operation: Uses a directional antenna to pulse a microwave out When the microwave hits a solid object, it reflects to the antenna on the gun where a receiver picks up the signal Quantitative principles of echoes and the Doppler Effect are then employed the calculate the speed at which the object is moving Operation of Radar Gun:  Operation of Radar Gun Stationary mode Moving mode The Cosine Effect:  The Cosine Effect If the target line is in a direct line with the police radar then measured speed will be exact. As the angle of incidence increases, if you move either right or left of this direct line, the accuracy of radar guns will decrease. The measured speed will decrease as you move off this centerline. This phenomenon is called the Cosine Effect. Contd…:  Contd… The Cosine Effect on moving mode radar is slightly more complicated and may measure target speed high under certain conditions Slide13:  Types of Radar Guns SOUND RADAR:  SOUND RADAR Is it possible to create something like a sound radar! Contd…:  Contd… But this won’t work because Sound will not travel very far in air. Every one can hear the sound. Thus..:  Thus.. Radar therefore uses radio waves instead of sound. Radio waves travel far and also invisible to humans. EXTRA:  EXTRA The television series Mythbusters has tested several methods of beating radar detectors not involving radar jammers. These methods are listed below: A person can beat police radar by waving a set of keys A person can beat police radar by hanging a disco ball from the rearview mirror A person can beat police radar by hanging CDs from the rearview mirror A person can beat police radar by covering the hubcaps in foil A person can beat police radar by covering the whole car in foil A person can jam police radar by placing LEDs on the front license plate A person can jam police radar with a Magnetron A person can beat police radar by shooting chaff behind the car A person can beat police radar by using spinning mirrors A person can beat police radar by painting the car black Slide18:  To sum up all these results, all the methods have been . . . Slide19:  BUSTED Conclusion:  Conclusion Use of traffic radar is widespread and we naturally assume that it is reliable. But there are big concerns about the accuracy. In the case of radar that is operated from a moving police vehicle the number of bad tickets may be as high as 30 percent! Police traffic radar doesn't tell its operator which object it is measuring or the direction that the object is traveling. References:  References Understanding Police Traffic Radar & Lidar (Paperback) by Les langford Method for High Precision Radar Distance Measurement and Synchronization of Wireless Units1318S. Roehr1, M. Vossiek2, P. Gulden1, 1Symeo GmbH, Munich, Germany, 2Clausthal University of Technology, Clausthal - Zellerfeld, Germany Radar Signals by Nadav Levanon, References…:  References… Weather Radar: Principles and Advanced Applications by peter meischner Information Networking: Networking Technologies for Broadband and Mobile Networks by Shigeki. Goto, Hyun-Kook Kahng Refrences….:  Refrences…. Ray Optics, Fermat's Principle, and Applications to General Relativity by Volker Perlick Optical Angular Momentum by Leslie Allen Advances in Sensing with Security Applications by Jim Byrnes Synchronization Systems in Communications and Control by William C Lindsey References ….:  References …. Introduction to Radar Systems - by Merrill Ivan Skolnik - Technology Slide25:  THANK YOU…….

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