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Phased Array Radars

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Electronic Scanning

Increased Data Rates
Instantaneous Beam Positioning
Elimination of Mechanical Errors
Multi-mode Operation
Multi-target capability

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.

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
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.
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

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