DRFM vs AESA

DRFM system designed to counter threats from missiles RF-guide (mostly technology PESA, purple-doppler), however some systems today are controlled or supported by technology AESA. For example, APG-79, Zhuk-AE, Type 305A. So DRFM material capable of defeating them?

A signal is a signal, it should not really matter how the antenna transmits and receives it, once it has left the antenna and is out in the wild then the antenna doesn't really matter until it receives it back.

 

If it's being replicated and possibly modified by the Jammer and retransmitted it should still mess with the radar.

A signal is a signal' date=' it should not really matter how the antenna transmits and receives it[/quote']

 

That is not really accurate. The more sophisticated the modulation scheme of the radar, the harder it becomes for the jammer to make the receiver think that the stuff it is feeding it is actually a return from a pulse it sent out itself.

Not true, once the signal has left the antenna then the antenna has no influence over it.

 

Modulation is not a property of the antenna, all the antenna does is transmit and receive, the modulation is done in the signal conditioning (modulator) before it is transmitted, and it is demodulated after the antenna has received it back.

 

...the harder it becomes for the jammer to make the receiver think that the stuff it is feeding it is actually a return from a pulse it sent out itself.

That's whole point of Digital Radio Frequency Memory Jammers, they record the signal, and adjust if needed and retransmit it, the Rx antenna knows no difference.

 

Basically whether the radar has an AESA antenna or not is irrelevant to DRFM jammers and what they do.

Edited May 30, 2015 by Cap'n kamikaze

One of the problems is detecting what you want to jam. You have a truckload of environment signals by default, and LPI techniques make it difficult to detect the source. From what I know it's also practically impossible to completely cancel out signals of this sort because the system can't be fast enough. Some level of degradation is probably possible but predicting interference at long ranges without accurate source ranging is equally impossible, you might even accidentally amplify the signal instead.

Basically whether the radar has an AESA antenna or not is irrelevant to DRFM jammers and what they do.

 

Not true, active phased arrays are able to frequency hop, something which a kleystron or magnetron pumped radar can not do. If you have enough memory and processing power, you can run complicated carrier frequency modulation schemes, the more elaborate, the harder it is to spoof the sender.

Frequency hopping is not a function of the antenna, and yes a Kleystron and magnetron can change frequencies, so in theory could if the hardware permits (enough channels) frequency hop, that should be obvious from the fact that there are peace-time channels on radar sets and war time ones, and each aircraft will be operating on a different portion of the radar bands otherwise they'd be jamming themselves.

 

You're making the mistake of not differentiating between the transmission element, and what happens before that and after that.

 

The whole point of AESA is that it does not take anywhere near as much time to slew the beam as a mechanical antenna does, hence why you can guide multiple SARH missiles to multiple targets, and is more adaptable on the back end, what it won't do is make any difference to a DRFM jammer, it will still receive the false signals from that just the same as a traditional non-AESA radar would, and it would not know the difference since the DRFM set is sending it back what it has just sent the DRFM.

Infact it has already been proved possible to jam the F-22's radar using DRFM, and that was done in 2009 with the avionics of the F-35 in testflight in a 737.

 

Frequency hopping only makes it harder, not impossible, especially since FH systems do not follow a true random sequence, given enough time (a few seconds) receiving the signal, a good signal analysis system would be able to find the sequence, and after that it will know what channels to transmit on and in what sequence, so jamming could then commence.

 

Radars advance, but so do ECM systems.

Frequency hopping is not a function of the antenna,

 

There's frequency hopping and there's frequency hopping. Under the klystron paradigm of a few (closely spaced) discrete channels, it is a lot easier to detect the system versus the almost seamless frequency range of an AESA radar.

 

The whole point of AESA is that it does not take anywhere near as much time to slew the beam as a mechanical antenna does,

 

This is a huge understatement. An AESA system is much more frequency agile than a system with a central microwave source (PESA, conventional antenna).

 

what it won't do is make any difference to a DRFM jammer, it will still receive the false signals from that just the same as a traditional non-AESA radar would, and it would not know the difference since the DRFM set is sending it back what it has just sent the DRFM.

 

 

Frequency hopping only makes it harder, not impossible, especially since FH systems do not follow a true random sequence, given enough time (a few seconds) receiving the signal, a good signal analysis system would be able to find the sequence, and after that it will know what channels to transmit on and in what sequence, so jamming could then commence.

 

Radars advance, but so do ECM systems.

 

I never said it was impossible. It basically comes down to how much processing power is available at either platform.

 

I still think you greatly underestimate the modulation possibilities. Given enough processing power, you can do a lot of fancy stuff there. Factoring in that you can spread the power over multiple frequencies simultaneously on an AESA, you give the Jammer much less SNR to work on. And determining a modulation pattern can become quite ressource intensive, since there's nothing keeping the transmitter from rapidly switching modulation patterns.

As I said, it has already been done.

 

The only modulation possibilities at such high frequencies are frequency shift, so in reality the modulation never actually changes.

 

You need to separate the idea of the antenna and the rest of the radar set.

 

Aall AESA really means is that it is steering the beam by changing the timings of each element, what happens before that (the modulation) is a seperate affair, so again, the DRFM jammer doesn't care if the beam it detects comes from an AESA set or not, it just detects the beam, records whatever it detects and retransmits it, and the AESA can't tell if the return is genuine or not if the spoof is identical to a genuine return.

 

AESA is not a magic bullet, and neither is Frequency modulation, again, ECM and ECCM are an arms race, the best you'll ever get is a temporary lead, and given the timescales of projects these days that lead will probably have been lost before anything gets into service.

As I said' date=' it has already been done.[/quote']

 

We know it's been done, but we don't know under what conditions it was done.. I would be extremely surprised if they had allowed that APG-77 to exercise its full capabilities as part of that test.

 

True, it's a constant back and forth between developments in radars vs. ECM, but LPI alone is enough to demonstrate that AESA radars still have the upper hand. If you can't recognize the signal as originating from a discrete emitter, your DRFM jammer isn't going to do anything about it. When "low probability" starts to become "ehh, somewhat lesser probability," the ball will be back in ECM's court.

Aall AESA really means is that it is steering the beam by changing the timings of each element, what happens before that (the modulation) is a seperate affair

[/Quote]

 

This is simply not true. You can not decouple the processing from the antenna if one type of antenna opens up much more possibilities.

 

AESA means that each Array element is a separate solid state TX/RX unit, as opposed to PESA, where the microwaves are created in a Klystron, magnetron or travelling wave tube. What you describe is PESA, which introduced beam forming techniques to actually steer the beam.

 

Solid state Transmitters are *far* more capable than Klystrons with regard to Modulation capabilities. Calling that a separate affair is simply wrong.

What I'm trying to say is once the beam has left the antenna no matter what type it is, then the antenna and the rest of the radar no longer matters, all that matters is the signal out there and whether the jammer can detect it, and copy it and retransmit it.

 

It really does not care if that beam came from an AESA array or not, infact it probably can't tell 100%, all it will know is it has a signal at a particular frequency coming in, at a particular power, and at a particular PRF, and if it changes frequency, or not, etc etc, you have to think of it from a signal POV.

 

It will see all that if it sees anything, and if its processing is good enough, it will reproduce it and retransmit it, and if it can then it will still jam it.

 

I would be extremely surprised if they had allowed that APG-77 to exercise its full capabilities as part of that test.

 

I think that is wishful thinking, if that was the case then why even use that radar at all, why not use another AESA like the APG-63V2/V3, if you're concerned about the security of the F/A-22's APG-77 why even use it?

 

There is no way to know, but I would be surprised if they didn't, you have to consider that the rest of the worlds airforces are also going the AESA route, so they're only going to be a few years behind, so it would make sense to test it against the current best of the best of the best with honours sir, and there is no point in nobbling it in that case, if you do then it's a fairly pointless test.