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?