Forum: General F-22A Raptor forum

Twenty years from now we will likely see lots of fighters equipped with AESA radars. One of the reasons AESAs are so desirable is that they have strong LPI modes. Will passive detection suites like the raptor's ALR-94 still be useful when adversaries have LPI? Is it possible to counter LPI?

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mil_hobbyist wrote:

One of the reasons AESAs are so desirable is that they have strong LPI modes.

They might have LPI modes.

Here is an interesting paper on the topic:

http://www.emrsdtc.com/conferences/2004 ... rs/A14.pdf

abstract:

"This paper discusses the current and projected future capabilities of “Low Probability of
Intercept” radars and of the intercept receivers used by Electronic Support Measures (ESM)
systems. In discussing the possible future sensitivity of the latter it makes use of the Matched
Incoherent Receiver to show how the intercept ranges may be able to increase in the future.
It then discusses future radar tactics which can make interception harder, and concludes that
there is no overwhelming advantage to one side or the other, but the balance will depend on
the particular tactical situation."

Enthusiast Joined: Oct 27, 2004 - 10:49 AM Posts: 70

mil_hobbyist wrote:

Is it possible to counter LPI?

If a radar is able to construct a signal to detect targets, then in theory that said signal can be jammed/detected. In practise it's like cracking the computer encryption: you might be able to crack the computer encryption / detect a signal but it takes more resources than is currently technologically available.

... and then someone comes up with a clever technology and an algorithm and shows that cracking the encryption takes seconds instead of eons and everything starts all over again. Laughing

There’s very little open source material on LPI other than the basics of the techniques but there is some material on detecting LPI emitters from such places as DTIC. The key is not to just detect the signal – I wouldn’t be surprised if current ESM systems can detect them now – it’s the ability to recognize that the signals are from an emitter and classify them as a specific class or type.

From what little there is out there, it appears that in order to do that you have to have a system that can capture and record the signal environment over a period of time to look for patterns. To classify the signal is even more difficult and in either case it requires quite a bit of memory and processing power. The key parameter seems to be time; most of these papers indicate it takes quite a bit of time for a system to capture enough of the signal to be able to classify it.

To me it would appear that AESA radars will continue to have the advantage with the progression of network warfare. If an ESM system requires quite a bit of time to detect and classify (in order the track) an emitter, what happens when the emission duties are distributed throughout the flight on a time share basis? For instance, imagine a flight of 4 Raptors taking turns with burst sweeps every 30 seconds for the whole flight? Each sweep will be different from the last and it’s highly likely that the pseudo random modulations are different from jet to jet.

So can the ALR-94 detect AESA emissions? Possibly but to me I wouldn’t count on it being useful against a similarly equipped foe at least at the moment.

BDF

Forum: General F-22A Raptor forum

AN/ALR-94 vs AESA