Active cancellation is an established technique used for example in noise-reducing headphones, and I think it is also used to quieten the passenger cabin of at least one small airliner.

The same technique is equally applicable at radar frequencies, but making an effective system probably depends being able to accurately predict your own RCS as seen by a threat radar, and being able to create steerable narrow beams of RF energy to create the required RF response.

To spoof a radar, the trick is to emit a signal that the identical to the reflection created by your own aircraft, but 180 degrees out of phase (anti-phase) with this reflected energy. The two signals effectively cancel each other out. Since the cancellation is done using the basic principles of physics, it should work with any type of enemy radar, irrespective of how clever that letter’s processing capabilities might be.

Generating a suitable cancellation signal requires an ability to accurately reproduce a anti-phase replica of the radar energy being reflected from your aircraft. Some differences between the two will be inevitable, so the cancellation will not be total. Some useful energy will still be receivable by the targeted radar. Like other stealth techniques, active cancellation reduces your radar cross section. It cannot eliminate all radar returns.

One problem with active cancellation is that it only works for the radar being spoofed. The radar returns ‘seen’ by other enemy radars that may be illuminating you will be unaffected. Another problem is that for all but the radar being spoofed, the activation of an active cancellation results in your aircraft emitting an RF signal.

The WW2 German maxim “Alles funkwerker ist landestverat” (all radio traffic is treason) comes to mind here. To avoid betraying your aircraft by this radiation, you’d need to confine the signal to a narrow beam directed towards the radar being spoofed. If this can be done, similar spoofing could in theory also be applied simultaneously to several other threat radars.

Exellent! You seem to be very well documented on this subject. It makes even more probable that spectra can have this kind of technology.

I am speculating here, but perhaps the construction of the four anechoic chambers (including the huge one) are made to precisely mesure the RCS of the rafale in order to use AC in an effective way.

when you reread sweetman’s article and your post it seems that there is a logic:

Spectra’s active jamming subsystem uses phased-array antennas located at the roots of the canards. Dassault has stated that the EW transmit antennas can produce a pencil beam compatible with the accuracy of the receiver system, concentrating power on the threat while minimizing the chances of detection.

and

But there is more to Spectra than conventional jamming. Pierre-Yves Chaltiel, a Thales engineer on the Spectra program, remarked in a 1997 interview that Spectra uses “stealthy jamming modes that not only have a saturating effect, but make the aircraft invisible… There are some very specific techniques to obtain the signature of a real LO [low-observable] aircraft.” When asked if he was talking about active cancellation, Chaltiel declined to answer.

Earlier this year, Thales and European missile-builder MBDA disclosed that they were working on active-cancellation technology for cruise missiles and had already tested it on a small unmanned aerial vehicle, using a combination of active and passive techniques to manage radar signature. This revelation makes it considerably more likely that active cancellation is already being developed for Rafale.

and

The complexity of active cancellation could account for Spectra’s high price tag, estimated in 1997 as “several billion francs” (equivalent to the high hundreds of millions of US dollars) for research and development. One of four Rafale prototypes was dedicated to Spectra tests, along with a Falcon 20 flying testbed. Four new large anechoic chambers were built to support the Spectra project, including one which is large and well equipped enough to operate the complete system in a fully detailed electromagnetic environment.

I recently read in A&C that EADS will perhaps use an active systems to diminish the vibrations of the four huge turboprop in the cabine of the A400M. It looks like it follows the same logic.

If AC is already available in some applications, I would be surprised that the military would not be intested to see some applications for their armed forces.

knowing the amount of money spent on spectra, and with the mystere 20 article in A&C, this rumor has some strong fundations I think.

This “rumor” stuff makes this subject fascinating.

But impossible to bring a definitive answer…

I am reaching the limit of uploaded files so save (if not already made) the pictures you want and I will add more later after reaching the limit.

PS: great pic scorpion! Do you know why there is this meeting?

most of the pictures are personnal from le bourget.

I can confirm Bill Sweetman’s statement that France has developed active stealth technologies for missile applications. This work was well under way in the late 1990s.

Around that time I too found myself at the receiving end of French hints that Spectra incorporates unspecified special capabilities, and observed how my mentioning active stealth caused the briefer to become extremely laconic.

very interesting! It will fuel the rumor again!:D

You were there as a journalist?

Hyperwarp : de nada!

This should be much better, forget the last attachement.

Hi everyone, just curious as to if the Rafale uses an ‘active cancellation’ type system to trick any radars that are painting it. I could swear i read several years ago now in various magazines that the Rafale was going to be fitted with such a system but in the last few years i’ve not heard a peep about it, I won’t pretend to understand how it works (got a slight idea) but as i understand it if it was made to work it would be a very very usefull tool for the rafale.

This rumor come from

Bill Sweetman, “Killer Angels”, Journal of Electronic Defense, November 2002

here is the article below:

Teeth of the Wind
The Rafale EW suite, known as Spectra, is one of the most powerful systems installed on a fighter aircraft and is intimately associated with the unique approach to stealth and survivability designed into the Rafale. Dassault executives describe the Rafale as discreet rather than being stealthy in the sense of a F-22. To avoid detection, it combines avionics, tactics, and reduced radar reflectivity with some techniques that have not been directly revealed and are apparently unique.

The first element of discretion is that Spectra’s receiver system and the FSO help detect and track targets without using radar. Spectra incorporates a radio-frequency (RF) detection system, a missile-approach warning sensor, and a laser-warning system and provides full 360-degrees coverage. The RF detection subsystem uses prominent square-section antennas, mounted on the lower corners of the engine inlets and in the rear of the fin-top pod, covering 120 degrees each. The receiver antennas use interferometric techniques to measure a signal’s angle of arrival within less than 1 degree and are designed so that they do not have a large radar-cross-section (RCS) contribution.

The Rafale is also designed to use terrain masking, particularly at night or in bad, weather when visually cued short-range surface-to-air weapons are less effective. With its maneuverability and a high degree of cockpit automation, the fighter is designed to fly a terrain-avoidance/threat- avoidance profile at 5.5 g and 100 feet in altitude. The RBE2 and a terrain-referenced navigation system, using stored terrain data, are used to provide redundant flight guidance.

Rafale makes extensive use of radar-absorbent material (RAM) in the form of paints and other materials, Dassault engineers have said. RAM forms a saw-toothed pattern on the wing and canard trailing edges, for instance. The aircraft is designed to so that its untreated radar signature is concentrated in a few strong “spikes,” which are then suppressed by the selective use of RAM.

Spectra’s active jamming subsystem uses phased-array antennas located at the roots of the canards. Dassault has stated that the EW transmit antennas can produce a pencil beam compatible with the accuracy of the receiver system, concentrating power on the threat while minimizing the chances of detection.

But there is more to Spectra than conventional jamming. Pierre-Yves Chaltiel, a Thales engineer on the Spectra program, remarked in a 1997 interview that Spectra uses “stealthy jamming modes that not only have a saturating effect, but make the aircraft invisible… There are some very specific techniques to obtain the signature of a real LO [low-observable] aircraft.” When asked if he was talking about active cancellation, Chaltiel declined to answer.

Earlier this year, Thales and European missile-builder MBDA disclosed that they were working on active-cancellation technology for cruise missiles and had already tested it on a small unmanned aerial vehicle, using a combination of active and passive techniques to manage radar signature. This revelation makes it considerably more likely that active cancellation is already being developed for Rafale.

Active cancellation is a LO technique in which the aircraft, when painted by a radar, transmits a signal which mimics the echo that the radar will receive – but one half-wavelength out of phase, so that the radar sees no return at all. The advantage of this technique is that it uses very low power, compared with conventional EW, and provides no clues to the aircraft’s presence; the challenge is that it requires very fast processing and that poorly executed active cancellation could make the target more rather than less visible.

The complexity of active cancellation could account for Spectra’s high price tag, estimated in 1997 as “several billion francs” (equivalent to the high hundreds of millions of US dollars) for research and development. One of four Rafale prototypes was dedicated to Spectra tests, along with a Falcon 20 flying testbed. Four new large anechoic chambers were built to support the Spectra project, including one which is large and well equipped enough to operate the complete system in a fully detailed electromagnetic environment.

This rumor was also fueled with the falcon 20 spectra testbed who remainded undetected while flying almost vertically to some modern radars during MACE X NATO surface to air exercise. (there was an article in the weekly Air&cosmos about it.)

I think it was fueled by another article stating that SPECTRA was one of france’s biggest black programme. It was mentionning the construction of a huge anechoic chamber.

I personnaly asked JPL very directly about the subject last june but he didn’t want to answer to any specific questions about SPECTRA. The only thing he said, was that SPECTRA is a key feature of the aircraft and that it was able to jam and “lure” at the same time which mean nothing and everything!

That is the history of this rumor. I guess any discussion would remained extremly speculative so better leave everyone with his own opinion about it!

I have few others:

a few other:

I don’t understand why you want to start a flame? just enjoy the pictures!

We don’t have access to first sources datas so any debate would be very speculative and subjected to strong tensions. We should better avoid another useless flame don’t you think?