Yet it is widely assumed that the supposedly reflective IRST of the Su-57 would give it away and turn it into non-stealthy. But an entire wing resonating in the frequency of a radar would not...
I know, I meant that I am not aware how the processing of the signal is made, if it is common based on more or less raw data at several frequencies or just a post-processing of the results of three separated radars.
True, still depending on the country it can help a lot, defending sea and land approaches to the country. But I agree the kind of users that really have a big need of them are big powers with big geographical extension where the radar is both protected inland and capable of covering directly the country borders.
Yes, it is not so ideal but still giving away your presence and bearing is extremely dangerous. All it takes to turn a phase interferometer into a tool for giving targeting info is that the enemy is not flying their planes alone but in couples or wings as it is normally done (not even considering ground passive locators of higher performance resources from the IADS helping there, which would be fully expected). First the radar signals give the direction, next the planes in the wing can separate a few km (or fly already in such way as is known from the MiG-31) and locate the enemy plane at the intersection of the directions their individual interferometers provide. You don't need to receive the same pulse at the different interferometers, since each of the platforms will make its own direction finding. Probably there are other tools like classification of the signal, analysis of the received power and so on, but the one I described above is more than enough IMHO.
That being said, my original points was not even the opponent getting purely passive, target grade information, but just knowing there is an enemy and where it is coming from. I think it is non disputable that a stealth plane does not use radar in scanning mode and would actually be extremely careful to use either it in a reduced sector or directional data links while trying to stay undetected.
