Transcript Phased Array Radars - University of Arizona NROTC
Phased Array Radars Naval Weapons Systems
Limitations of Mechanical Scanning Radars
Positioning Antenna is SLOW
Reduced reaction times
Blind Sided!
Mechanical error
Electronic Scanning
Increased Data Rates
Instantaneous Beam Positioning
Elimination of Mechanical Errors
Multi-mode Operation
Multi-target capability
Phased Array / SPY – 1D
Phase Concept Principle of Operation The electromagnetic energy received at a point in space from two or more closely spaced radiating elements is a maximum when the energy from each radiating element arrives at the point in phase.
Phase Relationships
Constructive Interference
Destructive Interference
Generating a Directional Main Lobe in a Phased Array Radar
Wave Fronts of Maximum Energy Boresight Axis Boresight Axis Radiating in Phase Altering the Phase to Change the Axis
Beam Positioning Point “P” where all waves arrive in phase P
Methods of Beam Steering
3 Kinds
Time Delay Scanning
Frequency Scanning
Phase Scanning
Methods of Beam Steering
Time Delay Scanning
Use of time delay to achieve the desired phase relationship
Time delay networks installed in front of each radiating element
Expensive, Complex & Heavy
Time Delay Scanning
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Methods of Beam Steering
Frequency Scanning
The physical length of the wave guide to delay the frequency interval
Vary the frequency about a base frequency
Very simple and relatively inexpensive.
AN/SPS-48
Frequency Scanning
Case #1 All Waves transmitted are in phase Case #2 Waves transmitted are phase shifted Wave guide feed horns Wave guide Wave guide
Methods of Beam Steering
Phase Scanning
Radiating elements fed by phase shifting networks (Phasers)
Phasers are electronically adjustable
More expensive than frequency scanning but cheaper than time delay
Most widely used – SPY1
SPY-1
Phase Scanning Phasers!!
Fleet Uses of Electronic Scanning
Ticonderoga
Arleigh Burke
SPS-48 Air Search
AN/SPS – 48
Angular Resolution
Cross-Range Resolution
Antenna beam width
Range
For accurate angular resolution need very long antenna (~10 km long!)
Motion of the transmitter/receiver simulates long antenna
SAR
Synthetic Aperture Array Radar * Uses the same theory of electronic scanning.
* Motion of the antenna used as the antenna aperture * Sequential instead of simultaneous * High resolution imaging from aircraft
SAR
Electronic Scanning Summary
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Multiple functions
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Search
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Track (so, TWS)
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Beam Steering Time delay, Frequency, and Phase scanning VERY BASIC LOOK AT ELECTRONIC SCANNING!
QUESTIONS?