How does Rafale's active radar cancellation work??

Pathfinder-X

Tribal Warlord
Verified Defense Pro
Dimensions
Wingspan 10.8 m
Wing area 45.70 square m
Length 10.3 m
Height 5.3 m
Weight
Empty weight 10 tons class
Maximum weight 24,500 kg
Internal fuel 4,500 kg
External fuel 7,500 kg
Max external capability 9,500 kg
External store stations:
Total 14
Heavy charges & fuel ("wet" stations) 5
g limits +9g/-3.2g
Max speed M 1.8+/750 knots
Approach speed 120 knots
Landing distance 450 m (1,475 ft)
Roll rate 270ø/sec
Max instant turn rate >30ø/sec
Max climb rate >1000 nautical miles
Combat air patrol loiter time >3 hours

SENSORS
The Rafale is equipped with an RBE2 radar, developed by Thales, which has look-down and shoot-down capability. The radar can track up to eight targets simultaneously and provides threat identification and prioritisation.
The optronic systems include the Thales/SAGEM OSF infrared search and track system, installed in the nose of the aircraft. The optronic suite carries out search, target identification, telemetry and automatic target discrimination and tracking.

COUNTERMEASURES
The Rafale's electronic warfare system is the Spectra from Thales. Spectra incorporates solid state transmitter technology, radar warner, DAL laser warning receiver, missile warning, detection systems and jammers.

if u guys look closely u'll see a retangular shape thing on the vertical fintail of rafale. i read it in a magazine called popular science, it said it sends out signals at half the radar wave lenth therefore erasing itself from the radar screen. how does this work?? anyone care to tell me??

 

gf0012-aust

Grumpy Old Man
Staff member
Verified Defense Pro
/excerpt on

To put this in the most primitive way, an air defense radar is transmitting at a certain frequency; the signal is bouncing off the aircraft; a receiver aboard the aircraft picks up the signal and a computer analyses its base frequency and modulations and an out-of-phase signal is generated by onboard systems to cancel out the enemy radar signal.

This is easier said than done, but theoretically it is possible. .....the main problem is that the incoming signal is complex and the reflection off the surface of the aircraft is even more complex. How do you cancel it out? How do you process so much information so quickly? But most importantly, how do you position transmitting antennae aboard the aircraft to cover the entire aircraft (since the enemy radar signal is reflected from a multitude of points on the airframe and it's reflected differently from every one of them).

/excerpt off
 

Pathfinder-X

Tribal Warlord
Verified Defense Pro
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oh i forgot to mention there r also two similar signal transmitter in front of the air intake.
 

gf0012-aust

Grumpy Old Man
Staff member
Verified Defense Pro
the issue still stands irrespective of how many transmitters it carries. I would have thought that the most efficient ARC would be a phased array system, it would need to be rather large and possibly would be someything that could be placed in the dorsal spine of an aircraft to achieve maximum effect. eg the Israeli F-16I's are runoured to have an on board weasel suite in their dorsal. It's also an issue of power generation, which is why I still think that a large on board phased array system would be more efficient.


some of the sweetman article follows:

This technique is a special type of "stealthy" ECM based on the principle of wave superposition. According to the article, Rafael has two antennas separated by the length of the aircraft. The antennas emit electromagnetic waves half a wevelength out of phase with the reflected radar signal, thus effectively reducing its intensity, making the aircraft virtually disappear from the radar's screen.

Active cancellation is a highly advanced and extremely complex process. This method is not known to be used on any military aircraft, though there were speculations that Russians may be using this technique on their S-37 and possibly MiG 1.42 prototype fighters. Also it is believed that the Northrop Grumman ZSR-63 defensive aids equipment installed on B-2 bombers may be using active cancellation.

Just how complicated it is to cancel a reflected radar signal can be seens from the fact that the original incoming signal from the radar will be reflected from many spots on the aircraft's body. Each spot will produce an individual reflection with its own, often unique, amplitude and phase. The amplitude of the reflection (high amplitude means that the relection would be easier to pick up than the one with lower amplitude) would depend on many factors, such as incident angle, particular type of material, geometrical form of a certain location on the aircraft's body that produced the reflectio and some other factors. The phase shift will be dictated by the wavelength of the radar signal and the location (and geometrical form) of the particular spot that produced the reflection in question.

The return signal, picked up by the radar, would look somewhat chaotic, consisting of background noise and "spikes". Background noise is produced by ionization levels of atmosphere, particular atmospheric conditions affecting scattering of electromagnetic waves of a given frequency, secondary reflections (weak signals). The "spikes" are produced by the strong reflections off the certain parts of the aircraftof a particular design.

These "spikes" is, presumably, the main target for active cancellation system. By removing these "spikes" from the radar screen the aircraftmay blend in with the background noise, which is normally ignored by the radar operators. It is important to understand, however, that in case of an effective active cancellation system we are dealing with an immensly complicated issue. Something that can be popularly explained with a single wave sinusoidal signal will become progressively more complex in real life situations.
 

Red aRRow

Forum Bouncer
Very interesting GF. This must be pretty damn hard to achieve, since calculating the type of reflection from each surface and point of the aircraft will be requiring quite a lot computational power. Please post any more information about it if you find it. Thanks.
 

gf0012-aust

Grumpy Old Man
Staff member
Verified Defense Pro
shamayel said:
Very interesting GF. This must be pretty damn hard to achieve, since calculating the type of reflection from each surface and point of the aircraft will be requiring quite a lot computational power. Please post any more information about it if you find it. Thanks.
that's why I think the Rafale solution is a minimalist response. I'd expect an aircraft like a B2 to have a better opportunity to generate proper cancellation power. (or as in the Israeli F-16's, the use of the entire dorsal area as a planar suite). You only have to look at the EW pods that non dedicated weasels carry to see how much power is required for s specific blanking task, getting a suite to reduce the RCS of an aircraft would be enormous. As soon as you added externals to it, you'd be furiously recreating another set of corrections to deal with a "dirty" platform. As soon as you launched, the config would need to be updated again (unless at that stage it becomes irrelevant)

There were some russian sites that dealt with the issue, most of the western sites don't discuss it in any detail except conceptually
 

Red aRRow

Forum Bouncer
I agree. I think the best way of achieving "stealth" (i.e. reducing your radar cross section) is to go the F-22 way of keeping your load in internal bays, while designing the structure to be of a lower visibility from any angle.

The way the Rafale seems to be achieving it would require the entire aircraft to be filled with ECM suites, computers and DSPs!!!
 

dabrownguy

New Member
It can try to mimic the wave as much as possible by doing one of the things a)finding out the wavelenght of the signal hitting the ac and off and then emitting a wave to cancle that out! complicated !
b)sending multaple waves that "could" match the wave given off. easy but not that effective.
This kind of stealth is too hard. I rather just scatter the signals and make the ac tailess and put a lot of compisotes.
 

adsH

New Member
if computational Power is an Issue then that wouldn't remain an obstacle for Long Specially the way Computers are advancing. I'd say Pick an Apple G5 dual 64 Bit processor system and mesh them up like 3 time or more then each unit at moment provides enough Processing power that is equal to the around 8 GHz in Pentium terms!! useing the israeli infiniBand Fiber optics to connect the Mesh up in DAta bus like connection would deliver enough power to do any sort of computational calculations. the Power consumption is low and i mean low, how would i know that? well i use one and it can literally do anything and everything at once and thats just one Unit. mesh them up and they will do anything what a Server does and much much better the Virginia Tech Universities Super computer is the Fastest built and the Smallest and the cheapest and the third fastest super computer and the only supercomputer that is built useing 1100 of the shelf dual processor Mac G5 computers linked up with israeli made inifiBand Fiber optical Network. so i think if people think more mainstream they can find of the shelf solutions to problems rather then wasting time on building hardware, just work on cleverer software.
 

gf0012-aust

Grumpy Old Man
Staff member
Verified Defense Pro
adsH said:
if computational Power is an Issue then that wouldn't remain an obstacle for Long Specially the way Computers are advancing. I'd say Pick an Apple G5 dual 64 Bit processor system and mesh them up like 3 time or more then each unit at moment provides enough Processing power that is equal to the around 8 GHz in Pentium terms!! useing the israeli infiniBand Fiber optics to connect the Mesh up in DAta bus like connection would deliver enough power to do any sort of computational calculations. the Power consumption is low and i mean low, how would i know that? well i use one and it can literally do anything and everything at once and thats just one Unit. mesh them up and they will do anything what a Server does and much much better the Virginia Tech Universities Super computer is the Fastest built and the Smallest and the cheapest and the third fastest super computer and the only supercomputer that is built useing 1100 of the shelf dual processor Mac G5 computers linked up with israeli made inifiBand Fiber optical Network. so i think if people think more mainstream they can find of the shelf solutions to problems rather then wasting time on building hardware, just work on cleverer software.
Processing power isn't the real issue. It's the algorithms necessary to make the hunches and effects that count. In real terms if you get the software and algorithms right then you would dedicate the activity to a RISC processor. Far more efficient, and less computational overheads.
 

adsH

New Member
gf0012 said:
adsH said:
if computational Power is an Issue then that wouldn't remain an obstacle for Long Specially the way Computers are advancing. I'd say Pick an Apple G5 dual 64 Bit processor system and mesh them up like 3 time or more then each unit at moment provides enough Processing power that is equal to the around 8 GHz in Pentium terms!! useing the israeli infiniBand Fiber optics to connect the Mesh up in DAta bus like connection would deliver enough power to do any sort of computational calculations. the Power consumption is low and i mean low, how would i know that? well i use one and it can literally do anything and everything at once and thats just one Unit. mesh them up and they will do anything what a Server does and much much better the Virginia Tech Universities Super computer is the Fastest built and the Smallest and the cheapest and the third fastest super computer and the only supercomputer that is built useing 1100 of the shelf dual processor Mac G5 computers linked up with israeli made inifiBand Fiber optical Network. so i think if people think more mainstream they can find of the shelf solutions to problems rather then wasting time on building hardware, just work on cleverer software.
Processing power isn't the real issue. It's the algorithms necessary to make the hunches and effects that count. In real terms if you get the software and algorithms right then you would dedicate the activity to a RISC processor. Far more efficient, and less computational overheads.
YOu know GF i have no doubt the Israelis have a Solution i have seen what they are capable of doing all my Lecturers who are Jewish or are from Israel work realy hard at researches and peculiarly they work in algorithm research, infact i was up all night Reading and revising for all those exam (that they set) i can truley appreciate how hard producing algorithms really are it take devotion and a great mind to prouce truely great algorithms.
 
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