There are three related radar technologies that have confusing names.
Phased Array Antenna means the shaping or focussing of the beam is done by feeding an array of emitters with a single high power feed at appropriate phase relationship. Here the phase relationship is fixed, so the beam points at a fixed direction with respect to the array. The beam is scanned by mecahnically moving the whole array
Electronically Scanned Array means the phase relationship is electronically varied to scan the beam without physically moving the antenna array.
Passive Electronically Scanned Array (PESA / PFAR in Russian) is the phase is changed passively using phase shifters and switches. Typically a single high power source is used which is passed through the phase shifters and fed to the antenna array.
There are two types of Active Electronically Scanned Array (AFAIK). One type is similar to PESA, but there are amplifiers in the individual antenna modules, so the phase shifting can be done at low power, resulting in better efficiency. AFAIK, the russian systems in development follow this route. I would be glad to be proven wrong there 🙂
The other AESA have individual modules generating its own signal. This system has a number of advantages over the others, including high efficiency and high agility of the beam. On the other hand this system arguably have lower S/N ratio.
S/N ratio :confused: ……can you explain that please….i got the rest of the reply though…thanks 🙂
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