AN/APG-77 vs DRFM jammer

Anything goes, as long as it is about the Lockheed Martin F-22 Raptor
  • Author
  • Message
Offline

exorcet

Active Member

Active Member

  • Posts: 154
  • Joined: 07 Oct 2009, 15:35
  • Location: US

Unread post01 Nov 2009, 04:40

I got into a bit a discussion elsewhere, and was wondering if I understand things correctly.

I'm arguing that the F-22 can defeat a DRFM since it has LPI and frequency hopping. I know DRFM can copy and send out false signals to manipulate/confuse a radar, but this implies that if the signal is impossible to detect or predict, DRFM cannot work, correct? So would the difficult to detect signal of the AN/APG-77 (or a LPI AESA in general) be able to reduce the effectiveness of DRFM systems?

I realize that classified information is not to be given out here (or anywhere), but I do not know if the answer to my question is allowed or not. If not, disregard this thread.
Offline

shep1978

Elite 1K

Elite 1K

  • Posts: 1395
  • Joined: 04 Apr 2009, 16:00
  • Location: UK

Unread post01 Nov 2009, 08:40

Sounds to me what you're saying makes a great deal of sense but im hoping like you are someone a bit more advanced in this field could help answer a bit more elaborately. Good question though!
Offline

Scorpion82

Elite 1K

Elite 1K

  • Posts: 1057
  • Joined: 07 Oct 2007, 18:52

Unread post01 Nov 2009, 13:22

Well in theory it can be jammed. LPI is fine, if it works as advertised but one has to take into account that the ECM department is further developing as well. It's certainly difficult to filter out a low power signal from background noise and as the signal characteristics are changing the jammer has to scope with it and reproduce the signal sequence correctly on time. It's definitely difficult, but not impossible.
Offline

SpudmanWP

Elite 3K

Elite 3K

  • Posts: 4795
  • Joined: 12 Oct 2006, 19:18
  • Location: California

Unread post01 Nov 2009, 17:10

Can a DRFM jammer operate on several frequencies simultaneously?

If not, then it cannot jam the APG-77, or 81.
"The early bird gets the worm but the second mouse gets the cheese."
Offline

Scorpion82

Elite 1K

Elite 1K

  • Posts: 1057
  • Joined: 07 Oct 2007, 18:52

Unread post01 Nov 2009, 17:25

SpudmanWP wrote:Can a DRFM jammer operate on several frequencies simultaneously?

If not, then it cannot jam the APG-77, or 81.


What is possible for a radar is certainly possible for a jammer as well, at least in theory.
Offline

SpudmanWP

Elite 3K

Elite 3K

  • Posts: 4795
  • Joined: 12 Oct 2006, 19:18
  • Location: California

Unread post01 Nov 2009, 17:41

The reason that the 77 & 88 can do multiple, simultaneous freq is because it is LPI AESA based.

For a DRFM jammer to be effective against the 77 & 81, then it will have to have enough CPU power to discover the multiple freqs and enough transmitters to cover all the freqs at the same time.
"The early bird gets the worm but the second mouse gets the cheese."
Offline

Scorpion82

Elite 1K

Elite 1K

  • Posts: 1057
  • Joined: 07 Oct 2007, 18:52

Unread post01 Nov 2009, 17:51

SpudmanWP wrote:The reason that the 77 & 88 can do multiple, simultaneous freq is because it is LPI AESA based.

For a DRFM jammer to be effective against the 77 & 81, then it will have to have enough CPU power to discover the multiple freqs and enough transmitters to cover all the freqs at the same time.


Is it actually using multiple frequencies at the same time against the same target? CPUs are much more capable nowadays when they were years ago when the 77 was designed and AESA jammers should do no worse in theory, except for power output as the jammer is usually weaker than the radar.
Offline

exorcet

Active Member

Active Member

  • Posts: 154
  • Joined: 07 Oct 2009, 15:35
  • Location: US

Unread post01 Nov 2009, 18:04

Scorpion82 wrote:
SpudmanWP wrote:The reason that the 77 & 88 can do multiple, simultaneous freq is because it is LPI AESA based.

For a DRFM jammer to be effective against the 77 & 81, then it will have to have enough CPU power to discover the multiple freqs and enough transmitters to cover all the freqs at the same time.


Is it actually using multiple frequencies at the same time against the same target? CPUs are much more capable nowadays when they were years ago when the 77 was designed and AESA jammers should do no worse in theory, except for power output as the jammer is usually weaker than the radar.

As far as I know, yes, the 77 sends out a random mix of frequencies and the receives multiple returns. It then pieces these returns together to make sense out of the signal.

I have no doubt that a DRFM can duplicate the F-22's radar (if detected), what I think is the bigger obstacle is the F-22's random frequencies. The DRFM can duplicate individual signals, but it can only send signals used by the F-22 in the past, and these of course will be useless or greatly reduced in effectiveness because the 22 would be using entirely different frequencies.
Offline

Scorpion82

Elite 1K

Elite 1K

  • Posts: 1057
  • Joined: 07 Oct 2007, 18:52

Unread post01 Nov 2009, 18:12

exorcet wrote:As far as I know, yes, the 77 sends out a random mix of frequencies and the receives multiple returns. It then pieces these returns together to make sense out of the signal.

I have no doubt that a DRFM can duplicate the F-22's radar (if detected), what I think is the bigger obstacle is the F-22's random frequencies. The DRFM can duplicate individual signals, but it can only send signals used by the F-22 in the past, and these of course will be useless or greatly reduced in effectiveness because the 22 would be using entirely different frequencies.


Well if it needs to piece the different returns together I wonder what happens to the output if some of those pieces are actually screwed by jamming signals. This could mean that even partitial jamming of some frequencies might fool the radar if it relies to much on assembling a proper signal from the various pieces.
Offline

SpudmanWP

Elite 3K

Elite 3K

  • Posts: 4795
  • Joined: 12 Oct 2006, 19:18
  • Location: California

Unread post01 Nov 2009, 18:17

That's what the RwR is for. Since the jammer is operating in the exact same frequencies as the radar, the RwR can easily detect and locate the jammer.
"The early bird gets the worm but the second mouse gets the cheese."
Offline

exorcet

Active Member

Active Member

  • Posts: 154
  • Joined: 07 Oct 2009, 15:35
  • Location: US

Unread post01 Nov 2009, 20:59

I don't think a proper DRFM will set off the RWR. A good DRFM will exactly copy the radar signal, so the RWR will think it's the aircraft's own signal and filter it out.

Scorpion, you raise a good point. I think it would have to do with how many of the frequencies are jammed, and how intelligent the AN/APG-77 is. If it's only a few frequencies, it might not matter. However, this doesn't allow the DRFM to predict the next set of frequencies. If the jammer just picks out a few and jams them, only 1 in every 1000 radar pulses (I made up numbers just for the sake of example) would be jammed. If the jammer wants to block out the 77, it would need to jam a whole range of frequencies, but that would make it more like a regular jammer, and not a DRFM, which would defeat the purpose. This would also allow it to be picked up by the RWR as SpudmanWP suggested.
Offline

SpudmanWP

Elite 3K

Elite 3K

  • Posts: 4795
  • Joined: 12 Oct 2006, 19:18
  • Location: California

Unread post02 Nov 2009, 01:29

A good RwR will recognize that the returning radar signal is higher than expected and keeps coming from the same point in space.

The "Cooperative EW" that is planned for the F-35 will also make this more of a possibility.
"The early bird gets the worm but the second mouse gets the cheese."
Offline

exorcet

Active Member

Active Member

  • Posts: 154
  • Joined: 07 Oct 2009, 15:35
  • Location: US

Unread post02 Nov 2009, 02:33

DRFM gets around that, it sophisticated enough to account for the difference in position of jammer and enemy radar. It can manipulate the radar into believing that the jammer is 200 miles out, when it's really 20 miles out.

A radar jammed by DRFM does not know it is being jammed because the jamming signal is basically identical to the returning radar signal bouncing off the illuminated aircraft.

Can you be more specific on Cooperative EW? Or are you just implying that the DRFM won't be able to send a signal to all members of an F-35 group, and that those not jammed will simply communicate to the others? I'm not sure about what limits a DRFM against a large number of planes.
Offline

SpudmanWP

Elite 3K

Elite 3K

  • Posts: 4795
  • Joined: 12 Oct 2006, 19:18
  • Location: California

Unread post02 Nov 2009, 02:55

I do not think you understand how hard it is to jam the APG-77 & 81. This is from the 2009 Northern Edge exercises where NG (Northrup Grumman) sent the BAC 1-11 test aircraft for APG-81 evaluation. Remember that this is early beta hardware and did not have the benefit of the other parts of the avionics package.

The Northrop Grumman AN/APG-81 active electronically scanned array (AESA) radar was flown on board the company's BAC 1-11 test aircraft and was integrated into what is considered the United States' largest and most complex airborne electronic warfare (EW) exercise to date. Northrop Grumman demonstrated the electronic protection (EP) capabilities of the AN/APG-81, by successfully countering advanced electronic attacks (EA), which are intended to degrade, neutralize, or destroy friendly combat capability.

"The radar was subjected to a scale of scenarios that far exceeded typical developmental or operational test program requirements," said Pete Bartos, a former U.S. Navy F/A-18 operational test director and currently Northrop Grumman program manager for fifth-generation fighter requirements, improvements and derivatives. "In the past, typical EP testing consisted of a few sorties versus a single or maybe two jammers at once. This test was unique in that it included flights versus multiple types of advanced jammers on several aircraft formations at once."
source
Offline

Scorpion82

Elite 1K

Elite 1K

  • Posts: 1057
  • Joined: 07 Oct 2007, 18:52

Unread post02 Nov 2009, 10:21

SpudmanWP wrote:A good RwR will recognize that the returning radar signal is higher than expected and keeps coming from the same point in space.

The "Cooperative EW" that is planned for the F-35 will also make this more of a possibility.


Modern ECM systems suit their signal power to the threat emitter, like the APG-77 does to reduce detectability.

With the cooperative jamming (lets sum it up as NCW) things will become even more complicated. Add to that sensor fusion and it might become impossible to jam the enemy.
Next

Return to General F-22A Raptor forum

Who is online

Users browsing this forum: No registered users and 3 guests