Radar Signal 1

8/12/2019 Radar Signal 1

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A SeminarOn

Radar Introduction and basic concepts

By

Arti D. ShindeMsc CS-IRoll No. 13120


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Outline

Introduction to radar Radar history

Radar principles

Radar System

Applications

Classification of Radar System

Radar Parameters

Two important concepts Ambiguity Function

Matched filter


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Radar history

First radar test (1904) German high frequency engineer Christian Hulsmeyer

Traffic supervision on water: he measures the running time ofelectro-magnetic waves to a metal ship and back

World War II Radar development underwent a strong push during W. W. II.

Radar was developed for military purposes during W.W. II.

The British used to radars to detect incoming bombers, locate

ships and airplanes During the war, radar operators found annoying blips continually

appearing on the radar screen. Scientists had not known thatradar would be sensitive enough to detect precipitations

Today, radar is an essential tool for predicting and analyzing the weather.


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Radar Principles

A radar does nothing but measures theround-trip time delaythe range R = c t / 2

radar: radio detection and ranging


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The radar beam can be focused to a specificdirectionazimuth and elevation

Radars work in high frequencies High resolution (small wavelengthsmall object)

Small antenna size

Mechanical rotation /phased-array


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Frequency ranges

Over the horizon(high power, lowresolution)

Airborne radar(small size, shirt range,high resolution)

GHz


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Radar System

All RADAR systems measure target characteristics, includingposition by transmitting electromagnetic energy and processing thereflected energy.

The major components of RADAR are the antenna, the trackingcomputer and the signal processor.

Qu. Explain the block diagram of modern RADAR system?


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Applications

The radar was actually built for military application and itfinds use in many applications in this field.

Mainly it is used in aircrafts, missiles, artillery projectiles,ships, land vehicles and satellites.

the radar is also use to control missiles to guide them to theirtarget.

The radar now is put to use in diverse applications and fieldslike weather monitoring, disaster control and monitoring andmany other applications.

This motivated us to understand the working of a modernradar system and more specifically, where and how DSP is putto use in.

Qu. Write a short note on Radar System and Radar applications?


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Classification of radar systems


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Radar Parameters

1. Antenna Aperture and Wavelength: The formula for antenna beam width is given by

where bis beamwidth, is wavelength, andDis antenna width. If the antenna geometry is symmetric, as in a parabolic reflector, then

same in both horizontal(azimuth) and vertical(elevation) dimensions.

2. Range and Range Resolution: The maximum unambiguous rangeRmaxis given by,

where c is velocity of light and Tis the pulse repetition interval. If Tis decreased, targets at ranges greater thanRmaxwill appear

after the next radar pulse has been transmitted causing anambiguity in the interpretation of measured range

Db

2max

cT

R


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Radar Parameters

3. Doppler Filtering:

Radars use Doppler frequency to extract target radial velocity (rangerate), as well as to distinguish between moving and stationary targets orobjects such as clutter.

wheref0is the carrier frequency, vis the target velocity, is thewavelength (c=f0), and fis the resultant shift in the received

frequency.

220 f

cf


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Ambiguity Functions

Radar signal design is directed toward achieving the best range and

velocity measurement on the one or more targets.

The ambiguity function is an idealized mathematical model of the system.

)1(nTs )(ts )(2)( tfjets )(2)(

nTsfjs enTs

Fig: Block diagram of the radar model leading the ambiguity function

Qu. Draw and explain the block diagram of radar model leading to AF?


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Ambiguity Functions

Ambiguity function A(,) is a two-dimensional function of delay andDoppler frequency that measures the correlation between a waveformand its Doppler distorted version:

The ambiguity function along the zero-Doppler axis (= 0) is theautocorrelation function of the waveform:


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Matched filter

Probability of detection is more related to SNRrather than the exact shape of the waveform

A matched filter maximizes SNR at the output of the filter


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Equality holds if and only if

Matched filter output:

Auto-correlation function


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The matched filter

Its impulse response is linearly related to the time-inverted complex-conjugate signal

When the input to the matched filter is the correctsignal plus white noise, the peak output is linearly

related to the signal's energy. At the peak output, the SNR is the highest attainable,

which is 2E / N0

The response is described by the autocorrelation

function of the signal


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MF response to Doppler-shifted signals

The AF describes the output of a matched filter when the inputsignal is delayed by tau and Doppler shifted by nu relative tonominal values for which the matched filter was designed.

Ambiguity function


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References

Theory And Application of digital signal processing

www.wikipedia.com
http://www.wikipedia.com/http://www.wikipedia.com/


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Thank you

Radar Signal 1

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