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Phased Array Radars

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

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Phased Array Radars

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  1. Phased Array Radars Naval Weapons Systems

  2. Limitations of Mechanical Scanning Radars • Positioning Antenna is SLOW • Reduced reaction times • Blind Sided! • Mechanical error

  3. Electronic Scanning • Increased Data Rates • Instantaneous Beam Positioning • Elimination of Mechanical Errors • Multi-mode Operation • Multi-target capability

  4. Phased Array / SPY – 1D

  5. 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.

  6. Phase Relationships • Constructive Interference • Destructive Interference

  7. Wave Fronts of Maximum Energy Beam Axis Boresight Boresight Axis Axis Altering the Phase to Radiating in Phase Change the Axis Generating a Directional Main Lobe in a Phased Array Radar

  8. Beam Positioning P Point “P” where all waves arrive in phase

  9. Methods of Beam Steering • 3 Kinds • Time Delay Scanning • Frequency Scanning • Phase Scanning

  10. 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

  11. Time Delay Scanning d

  12. 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.

  13. AN/SPS-48

  14. Wave guide feed horns Case #1 All Waves transmitted Wave guide are in phase Case #2 Waves transmitted are phase Wave guide shifted Frequency Scanning

  15. 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 Methods of Beam Steering

  16. SPY-1

  17. Phase Scanning Phasers!!

  18. Fleet Uses of Electronic Scanning • Ticonderoga • Arleigh Burke • SPS-48 Air Search

  19. AN/SPS – 48

  20. 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

  21. SAR

  22. 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

  23. SAR

  24. Electronic Scanning Summary • Multiple functions • Search • Track (so, TWS) • Beam Steering • Time delay, Frequency, and Phase scanning • VERY BASIC LOOK AT ELECTRONIC SCANNING!

  25. QUESTIONS?

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