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RADARRADARRadio DetectionRadio Detectionand Rangingand Ranging

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Excellence ThroughExcellence ThroughTeam WorkTeam Work

Pranav Bhadra 01Pranav Bhadra 01

Nirav Hemani 19Nirav Hemani 19

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What isWhat isRADAR ?RADAR ? Electromagnetic Device to detect and determine theElectromagnetic Device to detect and determine the

various parameters of the target .various parameters of the target .

Works on the principle of bouncing back the radioWorks on the principle of bouncing back the radiowaves from the target and the receiver of Radarwaves from the target and the receiver of Radarprocesses the required information.processes the required information.

Finds applications in Air Traffic Control, Navigation,Finds applications in Air Traffic Control, Navigation,

Military Surveillance, Ship and Vehicular Movements.Military Surveillance, Ship and Vehicular Movements.

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Parameters CalculatedParameters Calculated

by Radarby Radar Distance MeasurementDistance Measurement Speed MeasurementSpeed Measurement Location of the target with GPSLocation of the target with GPS

CoCo--ordinatesordinates Range of target with respect to groundRange of target with respect to ground Wind speedWind speed

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The Doppler EffectThe Doppler EffectChange in frequency ofChange in frequency of

the wave with respect tothe wave with respect to

a stationary observer anda stationary observer andmoving object.moving object.

Variation of frequency also depends onVariation of frequency also depends onthe direction the wave source is movingthe direction the wave source is movingwith respect to the observerwith respect to the observer..

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Block Diagram ofBlock Diagram of

Doppler RadarDoppler RadarThe transmitter transmitsThe transmitter transmits

a pulse of frequency fo.a pulse of frequency fo.

Receiver receives signalReceiver receives signalwith frequency of fo+fd.with frequency of fo+fd.

Receiver/mixer mixes signalReceiver/mixer mixes signalfrom STALO and receivedfrom STALO and receivedsignal.signal.

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Spread Spectrum TechniqueSpread Spectrum Technique

Technique by which the signal is spread in frequencyTechnique by which the signal is spread in frequencydomain, resulting in signal with wider bandwidth.domain, resulting in signal with wider bandwidth.

Method very effective in curbing distortion, jammingMethod very effective in curbing distortion, jammingand natural interference.and natural interference.

DSDS--SS and FHSS and FH--SS are methods involving SpreadSS are methods involving SpreadSpectrum technique.Spectrum technique.

Sharing of a single channel among multiple users.Sharing of a single channel among multiple users.

Reduced signal/backgroundReduced signal/background--noise level hampersnoise level hampersinterception.interception.

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Principle ofPrinciple ofOperationOperation The radar device transmits a wave whose band isThe radar device transmits a wave whose band isspread by a PN code from a PN generator, receivesspread by a PN code from a PN generator, receives

the reflected wave.the reflected wave. In this radar device, the received signal is spread to aIn this radar device, the received signal is spread to a

wide range is converted to a lowwide range is converted to a low--frequency bandfrequency bandwhich is easy to be measured by a down converter.which is easy to be measured by a down converter. The RADAR detects correlation between theThe RADAR detects correlation between the

received signal and the PN code.received signal and the PN code.

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Spread Spectrum RADARSpread Spectrum RADAR

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Explanation of the Block DiagramExplanation of the Block Diagram

oo Carrier GenerationCarrier Generation: Microwave Carrier is generated.: Microwave Carrier is generated.oo Transmit Code GenerationTransmit Code Generation: PN random bit stream of 1023 bits.: PN random bit stream of 1023 bits.oo BiBi--phase Modulationphase Modulation: Modulation of MW Carrier and PN bit: Modulation of MW Carrier and PN bit

stream via level shifter.stream via level shifter.

oo TransmissionTransmission: Modulated Wave transmitted through Antenna.: Modulated Wave transmitted through Antenna.oo Wave DemodulationWave Demodulation: Transmitting wave mixed with: Transmitting wave mixed with

demodulated.demodulated.oo Leak CancellationLeak Cancellation: Base Band domain instead of RF domain.: Base Band domain instead of RF domain.

oo CorrelationCorrelation: The correlation process has the net effect of: The correlation process has the net effect ofsuppressing all return signals that are of time delay differentsuppressing all return signals that are of time delay differentfrom that of the receive code by more than one clock period.from that of the receive code by more than one clock period.

oo Return signal analysisReturn signal analysis: The output of the correlator: The output of the correlator is a sum ofis a sum ofsinusoidal waveforms each resulting from the reflection of asinusoidal waveforms each resulting from the reflection of a

target.target.

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Determination of Target ParametersDetermination of Target Parameters: Target existence and speed: Target existence and speedin each range bin can be determined by the following process:in each range bin can be determined by the following process:

1. Set the time delay of the receive code relative to the transmit code according1. Set the time delay of the receive code relative to the transmit code accordingto the range bin of interest by the method as described in the correlationto the range bin of interest by the method as described in the correlationsection.section.

2. Apply spectrum analysis to return signal after a finite dwell time The2. Apply spectrum analysis to return signal after a finite dwell time The

theoretical minimum dwell time per range bin is dependent on the minimumtheoretical minimum dwell time per range bin is dependent on the minimumspeed of interest for the intended target type. In general, the dwell time perspeed of interest for the intended target type. In general, the dwell time perrange bin should be no less that one period of the Doppler Frequency ofrange bin should be no less that one period of the Doppler Frequency ofinterest.interest.

3. Determine the speed of target inside the range bin of interest according to its3. Determine the speed of target inside the range bin of interest according to its

Doppler frequency.Doppler frequency.

The direction of target movement cannot be derived from its DopplerThe direction of target movement cannot be derived from its Dopplerfrequency. It is possible to determine target direction of movement from thefrequency. It is possible to determine target direction of movement from theresult of successive skip scan and analyzing the pattern of target occupation ofresult of successive skip scan and analyzing the pattern of target occupation of

range bins. In this process the speed of each target can be tracked and used as itsrange bins. In this process the speed of each target can be tracked and used as itsidentifying parameter for tracking its movement.identifying parameter for tracking its movement.

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Block Diagram ofBlock Diagram of

DSDS--SS RadarSS RadarSoftware forSoftware forMeasurementMeasurementof Signalof Signal

StrengthStrength

SpreadingSpreading ScramblingScrambling RFRF

TransmitterTransmitter

Software forSoftware forMeasurementMeasurementof Signalof SignalStrengthStrength

DespreadingDespreading DescramblingDescrambling RFRF ReceiverReceiver

TargetTarget

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Brief Theory AboutBrief Theory About

Spread Spectrum RadarSpread Spectrum RadarSometimes pulse compression Radars have been calledSometimes pulse compression Radars have been calledspread spectrum Radars.spread spectrum Radars.

The baseband signal d(t), having bit rate of fb (= 1/Tb),The baseband signal d(t), having bit rate of fb (= 1/Tb),is first modulated in PSK modulator.is first modulated in PSK modulator.

Now this signal is spreaded (modulated again) byNow this signal is spreaded (modulated again) bypseudo noise (PN) signal having chip rate fc (= 1/Tc).pseudo noise (PN) signal having chip rate fc (= 1/Tc).

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The equation for spread spectrum signal isThe equation for spread spectrum signal is

V (t) = g(t)s(t) =(2Psg(t)d(t) cosV (t) = g(t)s(t) =(2Psg(t)d(t) cos t).t).

The spread spectrum signal is now up converted andThe spread spectrum signal is now up converted andtransmitted through transmitter antenna.transmitted through transmitter antenna.

At the receiver end the signal can be down converted, deAt the receiver end the signal can be down converted, de--spreaded and demodulated.spreaded and demodulated.

The deThe de--spreading is done through correlation process.spreading is done through correlation process.

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Patented RADAR technologies are now available that hasmajor advantages eliminating the most of the disadvantages ofeither pulse or continuous wave approaches.

These are based on the use of a digital pseudo-random binarycode, similar to the spread spectrum technology in wirelessmobile communications.

The technology uses DSSS signals to create noise like

modulation, making the transmitted signal virtuallyundetectable.

Spread spectrum radio has long been used in militarycommunications because of this advantage.

Overview of Spread Spectrum RADAROverview of Spread Spectrum RADAR

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Pulse Compression RadarPulse Compression RadarThe pulse compression nature of spread spectrum signalprocessing provides significant protection againstnormal Interference.

oHigh level of Multipath rejection.

oHigher reliability/efficiency and low power

consumption due to coding of the baseband pulses.

oLocal suppression of interference due to codedRADAR waveform and correlation of the receivedcode.

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Inefficiency ofInefficiency of

Conventional RadarConventional Radar Low frequency region of RADAR operation.Low frequency region of RADAR operation.

The problem of clutters.The problem of clutters.

Multipath & Interference.Multipath & Interference.

Inaccuracy in measurement of parameters.Inaccuracy in measurement of parameters.

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PN SequencePN Sequence It is a sequence of binaryIt is a sequence of binary

numbers, generating 0,1numbers, generating 0,1which appears to bewhich appears to berandom; but is in factrandom; but is in fact

perfectly deterministic.perfectly deterministic.

This property may be usedThis property may be used

for interdevice signaling,for interdevice signaling,shiftshift--register memoryregister memory--address identification, andaddress identification, andposition measurement inposition measurement inmachinery control, used inmachinery control, used in

Spread Spectrum Radar.Spread Spectrum Radar.

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Advantages ofAdvantages of

PN SequencePN Sequence Anti jammingAnti jamming Multipath Protection through BandwidthMultipath Protection through Bandwidth Multiple AccessMultiple Access Message Privacy: PseudorandomMessage Privacy: Pseudorandom

Selective CallingSelective Calling IdentificationIdentification NavigationNavigation Low Radiated Flux DensityLow Radiated Flux Density

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Applications ofApplications of

RADARRADAR Navigation.Navigation. To locate aircrafts, missiles.To locate aircrafts, missiles. Marine Radars to locate targets onMarine Radars to locate targets on

water.water. Police forces usePolice forces use radar gunsradar guns to monitorto monitor

vehicle speeds on the roads.vehicle speeds on the roads. Weather Forecasting.Weather Forecasting. Geologists using Ground PenetratingGeologists using Ground Penetrating

Radar.Radar.

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Microwave RADAR TechnologyMicrowave RADAR TechnologyInitial usage of microwave RADAR was for collision warningapplications on commercial vehicles, such as ambulances, busesand trucks.

The advantage of RADAR sensors, is that they perform equallywell during the day, the night, and in most weather conditions.

RADAR can also be used for target identification and fordetecting road conditions by making use of scatteringsignature information.

Most likely the RADAR sensors will be an integral partof any multiple sensor system, or sensor fusion, used toachieve a true autonomous vehicle.

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ConclusionConclusionThe Spread Spectrum RadarThe Spread Spectrum RadarIs far more efficient thanIs far more efficient than

the conventional Dopplerthe conventional DopplerRadar.Radar.

The use of PN Sequence inThe use of PN Sequence inDSDS--SS Radar improves theSS Radar improves theoverall performance inoverall performance in

functioning of Radar.functioning of Radar.