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Mensaje: <blockquote data-quote="Delfin" data-source="post: 632676" data-attributes="member: 2582">Te agradezco los aportes! AbrazoMás data:<a href="http://www.dassault-aviation.com/fileadmin/user_upload/redacteur/presse/lbg07/defense/rafale/Rafale.pdf">http://www.dassault-aviation.com/fileadmin/user_upload/redacteur/presse/lbg07/defense/rafale/Rafale.pdf</a>---------- Post added at 08:36  ---------- Previous post was at 08:24  ----------El RAFALE no es "sólo una cara bonita"... <a href="http://www.defencetalk.com/forums/showthread.php?t=1550">http://www.defencetalk.com/forums/showthread.php?t=1550</a>"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 reflection 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."---------- Post added at 08:37  ---------- Previous post was at 08:36  ----------The story of Active Cancelation started with Bill sweetman's article :Quote:<TABLE cellSpacing=0 cellPadding=6 width="100%" border=0><TBODY><TR><TD class=alt2 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">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. Spectra's RF systems are backed up by a laser-warning system, an optical missile-launch-warning system, and a full range of expendable countermeasures. </TD></TR></TBODY></TABLE>It was then commented by the specialist press :Quote:<TABLE cellSpacing=0 cellPadding=6 width="100%" border=0><TBODY><TR><TD class=alt2 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">According to the article by Bill Sweetman, published in Popular Science, French Rafael fighter may be using the so-called active cancellation technique to remain undetected by enemy radars. 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 wavelength 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 seen 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 reflection 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 reflection 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 aircraft of a particular design. These "spikes" is, presumably, the main target for active cancellation system. By removing these "spikes" from the radar screen the aircraft may 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 immensely complicated issue. Something that can be popularly explained with a single wave sinusoidal signal will become progressively more complex in real life situations. source: <a href="http://www.geocities.com/capecanaveral/9735/rafale1.htm">http://www.geocities.com/capecanaveral/9735/rafale1.htm</a> </TD></TR></TBODY></TABLE>This rumor was fuled when Spectra's testbed (a modified biz jet) remained undetected by modern SAM radar defenses during MACE X nato trials in the landes (southern france)It is supposed to be france's biggest black programme with several anechoic cambers build purposedely. It is sais that SPECTRA represents a high percentage of rafale price tag.it was then re-ignited by this :Quote:<TABLE cellSpacing=0 cellPadding=6 width="100%" border=0><TBODY><TR><TD class=alt2 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">Small excerpt from the book on the CEAM HP Grolleau, about Rafale's SPECTRA The head of the production of EPIGE (squadron programming and instruction for electronic warfare) speaking: "With Spectra, we entered the era of digital components of the interferometry for detection and Technology DRFM (digital radio frequency memory) for jamming. Without revealing any secret, I can tell you that thanks to all these advances, SPECTRA is able to scan a signal intercepted and transform/edit it in a almost-unlimited way for re-issue/re-sending it and create a frighteningly effective interference </TD></TR></TBODY></TABLE>This is the story of this Rumor...<img src="http://www.militaryphotos.net/forums/images/smilies/icon_smile.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /> fuente: <a href="http://www.militaryphotos.net/forums/showpost.php?p=3807593&postcount=259">http://www.militaryphotos.net/forums/showpost.php?p=3807593&postcount=259</a></blockquote>

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