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 ä Increased Data Rates ä Instantaneous Beam Positioning ä Elimination of Mechanical Errors ä Multi-mode Operation ä 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 ä Constructive Interference ä Destructive Interference

7. Generating a Directional Main Lobe 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

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

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

10. Methods of Beam Steering ä Time Delay Scanning ä Use of time delay to achieve the desired phase relationship ä Time delay networks installed in front of each radiating element ä Expensive, Complex & Heavy

11. Time Delay Scanning d

12. Methods of Beam Steering ä Frequency Scanning ä The physical length of the wave guide to delay the frequency interval ä Vary the frequency about a base frequency ä Very simple and relatively inexpensive.

13. AN/SPS-48AN/SPS-48

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

15. Methods of Beam Steering ä Phase Scanning ä Radiating elements fed by phase- shifting networks (Phasers) ä Phasers are electronically adjustable ä More expensive than frequency scanning but cheaper than time delay ä Most widely used – SPY1

16. SPY-1SPY-1

17. Phase Scanning Phasers!!

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

19. AN/SPS – 48

20. Angular Resolution ä Cross-Range Resolution ä Antenna beam width ä Range ä For accurate angular resolution need very long antenna (~10 km long!) ä Motion of the transmitter/receiver simulates long antenna

21. SARSAR

24. Synthetic Aperture Array Radar * Uses the same theory of electronic scanning. * Motion of the antenna used as the antenna aperture antenna aperture * Sequential instead of simultaneous * High resolution imaging from aircraft

25. SAR

26. Electronic Scanning Summary Multiple functionsMultiple functions SearchSearch Track (so, TWS)Track (so, TWS) Beam SteeringBeam Steering Time delay, Frequency, and Phase scanningTime delay, Frequency, and Phase scanning VERY BASIC LOOK AT ELECTRONIC SCANNING!VERY BASIC LOOK AT ELECTRONIC SCANNING!

27. QUESTIONS?QUESTIONS?