Phased Array Radars by NPA3Ui

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									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
         Think about this:
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 a
           point in phase.
    Phase Relationships


 Constructive
  Interference
 Destructive
  Interference
Generating a Directional Main
Lobe in a Phased Array Radar

      Wave Fronts of Maximu m Energy




                               Boresight                       Boresight
                                Axis                            Axis




     Radiating in Phase                    Altering the Phase to
                                            Change the Axis
Beam Positioning




                                     P


         Point “P” where all waves
         arrive in phase
 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

 
           d
  Methods of Beam Steering

 Frequency    Scanning
   The physical length ofthe wave guide
   to delay the frequency interval
           frequency about a base
   Vary the

   frequency
   Very simple and relatively inexpensive.
Frequency Scanning

                     Wave guide
                     feed horns


   Case #1
 All Waves
 transmitted
 are in phase
                  Wave guide



   Case #2
   Waves
   transmitted
   are phase
   shifted
                 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 – SPY!
    Phase Scanning




Phasers!!
  Fleet Uses of Electronic
  Scanning
 Ticonderoga
 ArleighBurke
 SPS-48 Air Search
AN/SPS – 48
    Synthetic Aperture Array
    Radar
* Uses the same theory of electronic scanning.

* Motion of the target used as the
  antenna aperture

* Sequential instead of simultaneous

* High resolution imaging from aircraft
ISAR
  Electronic Scanning Summary

• Electronic scanning is GROOVY!
   • Yeah Baby, Yeah!!!
• Multiple functions
   • Search
   • Track (so, TWS)
   • Beam Steering
• Time delay, Frequency, and Phase
  scanning
• VERY BASIC LOOK AT
  ELECTRONIC SCANNING!
QUESTIONS?

								
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