Phased Array Radar

Phased Array Radar
Advanced Mobile Robotics

Conventional Detection Platforms
• RADAR
• SONAR
• LIDAR

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Conventional Detection Limitations
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High Cost
Limited Resolution
Limited Scanning Frequency
Unwanted Interference
Mechanical Failure

What is a Phased Array Antenna?
• In wave theory, a phased array is a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.

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Passive vs. Active
• PESA: In a passive electronically scanned array (PESA), the microwave feed network in the back of the antenna is powered by a single RF source (magnetron, klystron,
TWT, etc.), sending its waves into phase shift modules
(usually digitally-controlled), which, in turn, feed the numerous emitting elements
• AESA: An AESA, instead, has an individual RF source for each of its many transmit/receive elements, making them "active."
• This provides for a graceful degradation, so that many
T/R modules may fail and the radar would not stop functioning. Antenna Concept
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An antenna array is a plurality of active antennas coupled to a common source or load to produce a directive radiation pattern Usually the spatial relationship also contributes to the directivity of the antenna
Use of the term "active antennas" is intended to describe elements whose energy output is modified due to the presence of a source of energy in the individual element 3

AESA Advantages
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Short to instantaneous (millisecond) scanning rates
Much higher range
Multiple agile beams: tremendous number of targets being tracked
Desirable low probability of intercept.
Solid state devices with vastly simpler mechanical designs
No complex hydraulics for antenna movement nor hinge appendages that are prone to