The reason why phased array were once called “active phased arrays” stems from a collision with classical antenna theory rather than radar-specific classifications. In fundamental electromagnetic engineering, an “active array” is defined as any antenna array where all radiating elements are fully driven meaning they are fed directly with radio frequency (RF) power. This is contrasted against a “passive” or parasitic array, which relies on elements that are merely excited by mutual coupling without a direct power feed .
Because phased array like a PESA directly drives all of its phase-shifted elements with RF power generated by a central transmitter, it technically qualifies as an “active array” under this older, foundational definition.
It was only when radar engineers needed a way to market and classify the new Transmit/Receive (T/R) module architecture that the definition of “active” was redefined within the aerospace industry to mean amplification at the element level (AESA), retroactively pushing PESA into the “passive” category.
They are certainly getting DL from the Irbis which is why i emphasised Irbis role.
But the reason i find it surprising that the seeker on R-77 or more speficially R-77-1 ( which is what we see on the video ) can lock low RCS is because we have documents for next generation seekers ( presumably R-77M ) providing public estimates on range against low RCS .
For instance as you can see here 9B-1103M2 is rated for around 2km lock range against 0.003m^2 targets. Considering thats quite a short range, it’s natural to question the capability of older seekers to lock such targets since they would lock at such short range that they would practically become SARH.
Of course there are other possibilities such as public domain numbers being understated or realistic RCS values for stated targets being order of magnitude higher. Im afraid we will not have the answer in the public domain for a long long time .
That isn’t even the full scale seeker, if you notice the diameter its only 100mm
And i remember that i did some maths, the normal mechanical seeker on R-77-1 fairs better iirc (mainly because the seeker mentioned here has quite a small in size)
It’s also worth noting that it isn’t out of the question for the 77M seeker to be AESA instead of PESA.
Despite the Main FCS Radar of most Russian fighter using a PESA (N035, N011R), things like Khibiny-M and the Multifunctoinal IFF Arrays are AESA systems. So they definitely have some experience making small AESA Systems. It would make sense for them to apply this to their Next-Gen Fox-3, especially considering that Russia is trying to make more AESA systems as a whole (like the AESA for Su-35S).
I had a chat about this with someone who knows MUCH more about radars than I do, and this is how he described it:
Basically, instead of one singular transmission source, they use multiple put together. Not like in AESAs where every antenna has its own T/R module, but generally a hundred or two antennas per T/R module.
Theres a few ways they can work from there, either using the whole thing effectively as one PESA, just with better receiver gain characteristics and reliability, or as set of multiple smaller PESAs, each one capable of making its own beam in a different frequency band. Although this does have limitations from decreasing the effective aparature as I said in one of my early messages.
