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Phased Array RadarsPhased Array RadarsPhased Array RadarsPhased Array Radars
Naval Weapons SystemsNaval Weapons Systems
Limitations of Mechanical Limitations of Mechanical Scanning RadarsScanning Radars
Limitations of Mechanical Limitations of Mechanical Scanning RadarsScanning Radars
Positioning Antenna is SLOWPositioning Antenna is SLOW Reduced reaction timesReduced reaction times Blind Sided!Blind Sided! Mechanical errorMechanical error
Electronic ScanningElectronic ScanningElectronic ScanningElectronic Scanning
Increased Data RatesIncreased Data Rates Instantaneous Beam PositioningInstantaneous Beam PositioningElimination of Mechanical Errors Elimination of Mechanical Errors Multi-mode OperationMulti-mode OperationMulti-target capabilityMulti-target capability
Phased Array / SPY – 1DPhased Array / SPY – 1DPhased Array / SPY – 1DPhased Array / SPY – 1D
Phase ConceptPhase ConceptPhase ConceptPhase Concept
Principle of OperationPrinciple of Operation
The The electromagnetic energyelectromagnetic energy received received
at a point in space from two or more at a point in space from two or more
closely spaced radiating elements is a closely spaced radiating elements is a
maximummaximum when the energy from when the energy from
each radiating element arrives at the each radiating element arrives at the
point point in phasein phase..
Phase RelationshipsPhase RelationshipsPhase RelationshipsPhase Relationships
Constructive Constructive InterferenceInterference
Destructive Destructive InterferenceInterference
Generating a Directional Main Generating a Directional Main Lobe in a Phased Array RadarLobe in a Phased Array RadarGenerating a Directional Main Generating a Directional Main Lobe in a Phased Array RadarLobe in a Phased Array Radar
Altering the Phase to Change the Axis
Boresight Axis
Beam Axis
Radiating in Phase
Boresight Axis
Wave Fronts of Maximum Energy
Beam PositioningBeam PositioningBeam PositioningBeam Positioning
PP
Point “P” where all waves arrive in phase
Methods of Beam SteeringMethods of Beam SteeringMethods of Beam SteeringMethods of Beam Steering
3 Kinds3 KindsTime Delay ScanningTime Delay ScanningFrequency ScanningFrequency ScanningPhase ScanningPhase Scanning
Methods of Beam SteeringMethods of Beam SteeringMethods of Beam SteeringMethods of Beam Steering
Time Delay ScanningTime Delay ScanningUse of time delay to achieve the desired Use of time delay to achieve the desired
phase relationshipphase relationshipTime delay networks installed in front Time delay networks installed in front
of each radiating elementof each radiating elementExpensive, Complex & HeavyExpensive, Complex & Heavy
Time Delay Scanning Time Delay Scanning Time Delay Scanning Time Delay Scanning
dd
Methods of Beam SteeringMethods of Beam SteeringMethods of Beam SteeringMethods of Beam Steering
Frequency ScanningFrequency ScanningThe physical length of the wave guide The physical length of the wave guide
to delay the frequency intervalto delay the frequency interval
Vary the frequency about a base Vary the frequency about a base
frequencyfrequency
Very simple and relatively inexpensive.Very simple and relatively inexpensive.
AN/SPS-48AN/SPS-48AN/SPS-48AN/SPS-48
Frequency ScanningFrequency ScanningFrequency ScanningFrequency Scanning
Wave guide feed horns
Wave guide
Case #1All Wavestransmittedare in phase
Wave guide
Case #2Waves transmitted are phase shifted
Methods of Beam SteeringMethods of Beam SteeringMethods of Beam SteeringMethods of Beam Steering
Phase ScanningPhase ScanningRadiating elements fed by phase-Radiating elements fed by phase-
shifting networks (Phasers)shifting networks (Phasers)Phasers are electronically adjustable Phasers are electronically adjustable More expensive than frequency More expensive than frequency
scanning but cheaper than time delayscanning but cheaper than time delayMost widely used – SPY1Most widely used – SPY1
SPY-1SPY-1SPY-1SPY-1
Phase ScanningPhase ScanningPhase ScanningPhase Scanning
Phasers!!
Fleet Uses of Electronic Fleet Uses of Electronic ScanningScanningFleet Uses of Electronic Fleet Uses of Electronic ScanningScanning
TiconderogaTiconderogaArleigh BurkeArleigh BurkeSPS-48 Air SearchSPS-48 Air Search
AN/SPS – 48AN/SPS – 48AN/SPS – 48AN/SPS – 48
Angular ResolutionAngular ResolutionAngular ResolutionAngular Resolution
Cross-Range ResolutionCross-Range ResolutionAntenna beam widthAntenna beam widthRangeRange
For accurate angular resolution need For accurate angular resolution need very long antenna (~10 km long!)very long antenna (~10 km long!)Motion of the transmitter/receiver Motion of the transmitter/receiver
simulates long antennasimulates long antenna
SARSARSARSAR
Synthetic Aperture Array Synthetic Aperture Array RadarRadarSynthetic Aperture Array Synthetic Aperture Array RadarRadar
* Uses the same theory of electronic scanning.* Uses the same theory of electronic scanning.
* Motion of the antenna used as the* Motion of the antenna used as the antenna aperture antenna aperture
* Sequential instead of simultaneous* Sequential instead of simultaneous
* High resolution imaging from aircraft* High resolution imaging from aircraft
SAR
Electronic Scanning SummaryElectronic Scanning SummaryElectronic Scanning SummaryElectronic Scanning Summary
• Multiple functionsMultiple functions• SearchSearch• Track (so, TWS)Track (so, TWS)• Beam SteeringBeam Steering
• Time delay, Frequency, and Phase Time delay, Frequency, and Phase scanningscanning
• VERY BASICVERY BASIC LOOK AT LOOK AT ELECTRONIC SCANNING!ELECTRONIC SCANNING!
QUESTIONS?QUESTIONS?QUESTIONS?QUESTIONS?