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Answered 2009-08-09 11:02:28

Passive Electronically Scanned Array (PESA) and the Active Electronically Scanned Array (AESA) are basically same in technology and principles of operation , both systems are capable of steer its beam Electronically through utilization of Phase Shifter hence it could be made in fully solid state configuration where no moving parts required (like APG-77 Radar on F-22 or Zhuk-AE Radar onboard MiG-35) they're only differs in source of Radio Frequency (RF) source The AESA uses multiple numbers of Radiating Elements where each of them have their own Transmitter and Receiver Module, making the Antenna where those modules located become "active" because it can Radiate by itself While the PESA system uses common RF source that usually found in conventional Radar like Klystrons, Magnetrons and Travelling Wave Tubes (this one especially, most common in Airborne Application like Fighter Radar). In Terms of Advantages the AESA system is typically better than PESA because of following factors : 1.because the Antenna Elements contain its own Transmitter and Receiver modules and located Right behind the Radiator, it would have lower or even No accidental loss , unlike her PESA sister which still require a connection to be made between its RF source to Radiating elements , incidental loss may occur. 2. High fault tolerance, failure of some modules will not hamper the operation of Radar (typical AESA Radar may contain 100++ Elements) however the entire device would fail if the failure occurs in 10% of total module counts.

3.No Single Point Failure , since basically each modules in active Version contains its own transmitter and Receiver modules, the passive device however since it still use single Transmitter device like Traveling Wave tube , failure of the transmitter may hamper the RADAR operations

Answers by :Xenostrike 06 a.k.a Stealthflanker an Illegally Banned member from Electrosphere

EDIT- Bit improvements and adding single point failure in previous answer

Just to help point the above answer at the questions Passive systems have a single point of failure in its transmit devices (Travelling Wave Tubes,Wave Guides, Microstrips and Power Dividers as well as Antenna Feed System) . Active antenna do not have a single point of failure and a meant to degrades performance gracefully except probably malfunctions in its tapering systems or when the beam is steered in very high deflection angle which will reduce antenna effective Area, increase beamwidth hence reducing gain an compromise detection range. Active versions are much more flexible as phase can be varied in each or a groups of Radiating elements to create different waveforms or beamshapes .

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