EE200_radar_gun

EE200_radar_gun - EE 200 Lab 6 - Speed Trap 1 Introduction...

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Last Revised: 11/10/2008 1 EE 200 Lab 6 - Speed Trap 1 Introduction In this lab you will be given two raw data signals representing the signals received by a radar gun aimed at a moving object. Using the first signal you will perform Fourier analysis along with the Doppler effect to find the speed of the moving object. The second signal is similar to the first but uses a signal transmitted at a slightly different frequency. This slight shift will illustrate the concept of spectral leakage. 2 What you will learn You will learn to use Fourier analysis (frequency domain) methods and understand their properties to extract useful information from a signal. In addition, basic concepts of modulation (in this lab we only focus on amplitude modulation rather than FM or other methods) will be introduced. 3 Background Information and Notes Radar Guns and the Doppler Effect : Radar guns emit a signal at a particular frequency, then capture the echo returned by an object. The Doppler-effect describes the phenomenon that a frequency shift takes place when the signal echos off of a moving object. The amount of the frequency shift depends on the velocity of the object. Using the Doppler-shift effect, we can measure the frequency shift and thus calculate how fast the object was moving. The velocity of the moving object is related to the original frequency and the frequency shift by, Here, c is the speed of light (6.71E8 miles per hour), f 0 is the original frequency of the emitted signal and Δ f is the difference in the returned echo’s frequency from the original frequency. Note in the equation above v is the component of the velocity that is head-on to the angle of the radar gun (i.e. if the object is traveling normal to the signal propagation, there will be no frequency shift. However, we will assume
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This note was uploaded on 04/05/2009 for the course EE 30446 taught by Professor Zadeh during the Spring '08 term at USC.

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EE200_radar_gun - EE 200 Lab 6 - Speed Trap 1 Introduction...

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