Interferidores

[AlbertoRJ]

Santiago, Dizem que o Spectra custou quase um terço de tudo o que foi gasto no desenvolvimento do Rafale. O que dá uma idéia de como esses sistemas EW são sofisticados (e caros!).

[]'s

[AlbertoRJ]

Uma pesquisa no Google, mas é interessante:

Active Radar Cancellation

ACTIVE CANCELLATION

A method of passive cancellation of the reflected radar signalwas already discussed, together with its shortcomings. A far more flexible but also more complex approach is to activelyreplicate the incoming signal and reverse its phase in order toachieve the same effect. Since it involves active emissions,this technique is more appropriately classified as part of theactive jamming effort, but is nevertheless noteworthy withregards to stealth because its net effect is the reduction (or even complete elimination)of the amplitude of the reflectedsignal, and thus the reduction of the targeted object’s apparent RCS.
Just how complicated it is to cancel a reflected radar signalcan be reasoned from the fact that the original incoming signalfrom the radar will be reflected from many spots on theaircraft's body. Each spot will produce an individual reflectionwith its own unique amplitude and phase. The amplitude of the reflection would depend on many factors, such asincidence angle, particular type of material, geometrical formof a certain location on the aircraft's body that produced thereflection and some other factors. The phase shift will bedictated by the wavelength of the radar signal and the location(and geometrical form) of the particular spot that produced thereflection in question. The enemy radar does not, however,receive all of the reflected variations of the original signal asseparate entities. It either selects the strongest return signal, or averages several strongest reflections. This simplification can be used to the advantage of the aircraft, since it will only needtwo antennas to transmit a simulated return signal averagedover the length of the aircraft. The return signal, pickedUp by the radar, would look somewhat chaotic, consisting of background noise and the main return spikes. These spikesare, presumably, the main targets of active cancellation (hereagain we see the importance of first shaping the aircraft tominimize and actively control the formed spikes). It isimportant to understand, however, that in case of a real-world effective system we are dealing with an immenselycomplicated issue. Something that can be popularly explainedwith a single wave sinusoidal signal will becomeprogressively more complex in real-life situations.Active cancellation as a working method places strongemphasis on several things to happen properly:

* The aircraft has to have a system capable of analysing theincoming signal in real-time and replicating itscharacteristics faithfully enough to disguise itself as the“true” signal, before its phase is reversed. Analysing thesignal on first contact is not enough; the enemy is likelyto shift the emission characteristics of the radar equipment within its physical limits (PRF, signalfrequency etc.) throughout the duration of the detection/tracking attempt. Likewise therefore, theanalysis process has to be repeatedly performed as long asthe aircraft remains within the detection envelope of theemitter.

* The phase-reversed signal must be transmitted with justenough power to match the “real” signal reflected back atthe receiver. Careful power management is crucial here; aclever software algorithm in a modern radar system maytry to check the signal strength difference betweenincoming spikes and reject those that seem a bit “toopowerful” for the given situation. The purpose here isdeception, not to flood the other guy’s scope with white-noise static.

* The bearing of the incoming signal must be determinedaccurately so that the “fake” reflection will be reflected atthe original transmitter and nowhere else. This alsoimplies a very accurate laying of the onboard beam-transmitter for the fake signal, as well as rapid beam-steering for circumstances where the airframe’s attitudeand velocity vector is rapidly changing(e.g. whilemanoeuvring to avoid enemy fire). This is easier said thandone: it is hard enough to precisely locate (in bothazimuth and elevation) the emitter in order to point thefake signal only there and nowhere else; let alone keepingthe beam on-target while the aircraft is performinganything from routine subtle navigation courseadjustments to gut-wrenching missile-avoidancemanoeuvres. For this reason, only an electronic-scan arrayis practically suitable for emitting the fake signal.

Despite this tall order of requirements, active cancellation offersseveral advantages compared to more conventional jammingtechniques. Both barrage and deception jamming cannot avoid tipping-off the enemy on “something” going-on; here, however,the element of surprise is fully retained for exploitation. Asignificantly less amount of transmission power is required, onlyenough to replicate the weak energy reflection back to the enemyemitter; thus the overall system can be light and compact enoughto be fitted to aircraft hitherto unable to benefit from the existenceof heavyweight jammers. This also means that other onboardavionics are significantly less hampered by RF-interference whileactive cancellation is in progress (those who recall the EW-avionics interference troubles of aircraft such as the B-1, the EF-111, the Su-27 or the EA-6 will certainly appreciate this).

The Spectra integrate dew suite on the Rafale fighter is a primeexample of active cancellation. All the elements described aboveare in place: sensitive and precise interferometers for passivedetection & localization, powerful signal processors as part of theoverall avionics suite, and conformal electronic-scan arraysdedicated to the transmission of EW signals. Combining a semi-stealthy airframe structure (treated with RAM in significantquantities) with various traditional forms of jamming plus activecancellation can result in an airborne weapons platform of vastlyLower RCS than one would expect from an otherwise “ordinary-looking” canard-delta aircraft.

There have been speculations that the Russians may be using thistechnique on their S-37 Berkut and possibly MiG 1.42 prototypefighters. It is also believed that the ZSR-63 defensive aidsequipment installed on B-2 bombers may be using this technique.It is not clear whether the F-22and F-35 are going to employactive cancellation in their EW arsenal. Certainly the pieces are inplace hardware-wise: An added bonus of the AESA radars fittedon both aircraft is that the operation of multiple RF beams inparallel(as opposed to the single beam of mechanical-scan andpassive electronic-scan systems) enables the radar to scan, track and jam at the same time. It is however unknown if the relevantsoftware is going to be in place to exploit this capability.Certainly the F-22 is more than capable of performing thisfunction with its ultra-sensitive ALR-94 receivers and ampleonboard processing power, in addition to the large AESA set.
Whether the significantly smaller and thus volume/weight-challenged F-35 will be able to perform the function on its ownhardware remains to be seen.

A Seminar Report On Stealth Technology In Aircraft - CSJM University Kampur
http://pt.scribd.com/doc/51581190/2/ACTIVE-CANCELLATION

4. Active Cancellation

Active cancellation involves the process of modifying and retransmitting the
received radar signal. The target must emit radiation in the same time with the received
pulse whose amplitude and phase cancel the reflected energy. The required data are the
angle of arrival, intensity, waveform and frequency of the received wave. An active
cancellation system should sense these data accurately and then reradiate the pulse with
proper amplitude and phase. Obviously, this requires a challenging task for the system, as
the frequency increases the work becomes much more difficult.
There are two levels of cancellation:
1. Fully active: The cancellation network receives, amplifies, and retransmits the
threat signal such that it is out of phase with the static RCS of the target. The transmitted
signal amplitude, phase, frequency and polarization can be adjusted to compensate for
changing threat parameters.
2. Semiactive: No boost in threat signal energy is provided by the cancellation
network, but passive adjustable devices in the network allow the reradiated signal to
compensate for limited changes in the threat signal parameters [2].
The demands for a fully active system are almost always so severe as to make it
impractical. It requires a transmitter and antennas that cover the anticipated threat angles,
frequencies, incident power densities, and polarization. Knowledge of the threat direction
is required, as well as the target’s own RCS. A semiactive system is not as complicated
in terms of hardware, but the use of adjustable devices still requires bias lines, controller
units, and a computer with the appropriate data bases [2].


RADAR ABSORBING MATERIAL DESIGN - Thesis (Naval Posgraduate School)
http://www.dtic.mil/cgi-bin/GetTRDoc?Lo ... =ADA418302

Active cancellation stealth analysis of warship for LFM radar

ABSTRACT

Active stealth of warship is an important developing direction in modern stealth technology field. Based on scattering properties of warship and characteristics of linear frequency modulated (LFM) signal and its matched filter, the cancellation signal was designed. Warship stealth was achieved through interference cancellation between cancellation signal and radar echo signal. Simulation results show that complete stealth of warship can be achieved through canceling LFM echo signal, and the scattering field of warship can be reduced by almost 10 dB even with some cancellation error. The proposed method can provide important reference for warship's active stealth in project realization.
http://ieeexplore.ieee.org/xpl/freeabs_ ... er=5655941

Active radar stealth device

United States Patent 5036323

1. An active radar stealth device mounted on a host platform for minimizing the radar cross-section of the host platform, comprising:
a. a coating on a surface of the host platform wherein said coating is essentially transparent with respect to a microwave field incident on said coating, said incident microwave field passing through said coating and reflecting off the host platform to form a reflected microwave field;

b. means contained within said coating for detecting a combination of: (1) said incident microwave field, (2) said reflected microwave field and (3) a canceling microwave field; and

c. means contained within said coating for producing said canceling microwave field in response to said detected combination.



2. An active radar stealth device as in claim 1 wherein said detecting means is exposed to said incident microwave field at a surface of said coating.

3. An active radar stealth device as in claim 1 wherein said detecting means is located further from the host platform than said producing means.

4. An active radar stealth device as in claim 1 wherein said coating is plastic.

5. A device mounted on a host platform for modifying a microwave radiation response of the host platform comprising:
a. a coating on a surface of the host platform wherein said coating is practically transparent with respect to a microwave field incident on said coating, said incident microwave field passing through said coating and reflecting off the host platform to form a reflected microwave field;

b. at least one microwave detector contained within said coating for detecting a combination of: (1) said incident microwave field, (2) said reflective microwave field and (3) a modifying microwave field at said detector;

c. means, in electronic communication with each of said detectors, for producing a control signal in response to said detected combination; and

d. at least one microwave emitter contained within said coating wherein said emitter is adjacent to said detector to form a detector/emitter pair, said emitter producing said modifying microwave field in response to said control signal wherein said modifying microwave field modifies the microwave radiation response of the host platform at said detector.



6. A device as in claim 5 wherein said coating is plastic.

7. A device as in claim 5 wherein said microwave detector and microwave emitter comprise piezoelectric plastic.

8. A device as in claim 5 wherein said detector is located further from the host platform than said paired emitter.

9. A device as in claim 5 wherein said control signal means is a phase inverting amplifier whereby said modifying microwave field produced by said emitter is 180° out of phase with respect to said detected combination.

10. A device as in claim 5 wherein said detector is exposed to said incident microwave field at a surface of said coating.

11. A device as in claim 5 wherein said control signal means is a multiplier.

Description:
ORIGIN OF THE INVENTION

The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon or therefore.

FIELD OF THE INVENTION

This invention relates generally to radar stealth and in particular to an active radar stealth device.

BACKGROUND OF THE INVENTION

Stealth, as it applies to radar systems, refers to the minimization of one's radar cross-section. Currently, most stealth systems in development or production are based upon passive, or absorptive approaches, where specialized structural design methods are combined with the use of microwave absorptive coatings. Although success has been achieved with this method, there are still a great deal of problems. Often, the structural design having the smallest radar cross-section will not be the most efficient aerodynamic design, thereby diminishing the performance characteristics of the aircraft. Similarly, while structural design methods are effective in reducing the cross-section of relatively small systems such as an aircraft, they become impractical when attempting to reduce the radar cross-section of something significantly larger and more geometrically complicated, such as a ship. Furthermore, there can still be a significant amount of RF energy reflected from the absorptive coatings.

An active radar stealth technique, known as electronic counter measure (ECM), involves active manipulation of RF signals. However, current systems are limited by the physical properties of metallic based antennae and structures. In these systems the incoming RF signal will be reflected from the metallic skin of the aircraft/ship before an active device on the aircraft/ship can modify the signal and manipulate it or repeat it back to the source. Thus, there is no opportunity for stealth, although there can be cover and deception.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a radar stealth device that minimizes the radar cross-section of any object under radar surveillance.

It is a further object of the present invention to provide a radar stealth device that permits an efficient functional design while providing the advantages of stealth protection.

Other objects and advantages of the present invention will become more apparent hereinafter in the specifications and drawings.

In accordance with the present invention, an active radar stealth device, mounted on a host platform, minimizes the radar cross-section of the host platform. A plastic coating, practically transparent with respect to an incident microwave field, is provided on the surface on the host platform. The incident microwave field passes through the coating and reflects off the host platform to form a reflected microwave field. A microwave detector is contained within the coating and detects a combination of the incident microwave field, the reflected microwave field, and a canceling microwave field. A microwave emitter adjacent to the microwave detector and contained within the coating produces the canceling microwave field in response to the detected combination. The canceling microwave field is a microwave field that is 180° out of phase with respect to the detected combination in order to provide a theoretical radar cross-section approaching zero at the microwave detector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the active radar stealth device according to the present invention; and

FIG. 2 is a cross-sectional view of the active radar stealth device according to the present invention showing the incident microwave field, reflected microwave field and canceling microwave field.

DETAILED DESCRIPTION OF THE INVENTION

Microwave radiation generally refers to radiation residing above 1 GHz in the radiation spectrum. This would include many types of radar systems such as L-, S-, C-, X-, K-, Ku- and Ka-bands as well as the experimental microwave bands up to and beyond 300 GHz. The present invention is designed to be operational in any and all of these frequencies. Referring now to the drawings, and in particular to FIG. 1, an active radar stealth device 10 according to the present invention is shown exposed to an incident microwave field 30. The device 10 consists of a coating 11 on a surface 15 of a host platform 13. For ease of description host platform 13 is shown only in section and may be the outer surface of any object under radar surveillance. Typically, host platform 13 is an aircraft, ship or other vehicle. The choice of material for and shape of host platform 13 is not a design constraint of the present invention. Indeed, this is one of the great advantages of the present invention since the design of host platform 13 is independent of stealth considerations and may therefore be optimized for its specific purpose.

The coating 11 is a microwave field semi-transparent coating attached to the surface 15 of host platform 13. Attachment must be effected by the use of an epoxy glue, or it may be heat-sealed directly to the surface 15. Indeed, any attachment mechanism may be used as long as the affect on microwave fields reflected from the surface 15 is minimal and uniform. While the surface 15 is shown as being flat, it is not so limited. Indeed, another advantage of the present invention is its ability to provide stealth regardless of the host platforms surface contours. Ideally, coating 11 would have a coefficient of transmission of 1 and coefficient of reflection of 0 in order to be essentially transparent with respect to the microwave fields. Typically, coating 11 is a plastic composite. Other materials may be chosen for coating 11 depending on such design constraints as the expected radar environment, cost, ability of the material to adapt to the particular shape of the host platform surface 15, etc.

Mounted within coating 11 are a microwave detector 17 and a microwave emitter 19 rigidly held in a spaced apart relationship with one another by coating 11. Both detector 17 and emitter 19 are typically constructed as an "RF conductive patch" and deposited on a thin-film material. They should also have a small radar cross-section with respect to the surface 15 of host platform 13. For example, if host platform 13 is an aircraft or ship made of metal or metal alloys, detector 17 and emitter 19 might be thin-film piezoelectric plastic patches. While detector 17 is shown to be exposed directly to the incident microwave field 30, its placement is not limited thereto. Detector 17 may also be located completely within coating 11. The location relationship between detector 17 and emitter 19 will be discussed further herein below.

For ease of description, the present invention will be described for a single detector/emitter pair 17/19. However, in practice, the present invention will make use of a plurality of these pairs throughout the coating 11. Since each pair functions independently and in identical fashion, a functional description of the present invention will be provided by reference to the single detector/emitter pair 17/19.

A phase inverting amplifier 20 is connected between detector 17 and emitter 19. While amplifier 20 and associated wiring 21 is shown to reside totally within coating 11, the invention is not so limited. For example, amplifier 20 might be located inside the host platform 13 or may even be integrated into one or both of detector 17 or emitter 19. The microwave field, which will be described in greater detail herein below, detected by detector 17, is inverted by amplifier 20 to be 180° out of phase with respect to the detected field. In turn, emitter 19 propagates the phase inverted field out into the coating 11 to cancel the detected microwave field. Alternatively, amplifier 20 might be any signal modifying amplifier depending on the desired type of canceling microwave field. For example, amplifier 20 might be a multiplier in which case emitter 19 would propagate a microwave field much greater than that detected by detector 17. In such an operational mode, the present invention would provide deception and cover.

In operation, the microwave field detected by detector 17 is a combination of three microwave fields. Referring now to FIG. 2, amplifier 20 and its associated wiring 21 have been removed for ease of description. Detector 17 detects a combination of incident microwave field 30, reflected microwave field 32 and canceling microwave field 34. Reflected microwave field 32 is the reflection of incident microwave field 30 off host platform 13. Canceling microwave field 34 is the canceling microwave field produced at emitter 19 and is 180° out of phase with respect to the detected combination at detector 17. Thus, the canceling microwave field 34 is also a feedback input detected by detector 17 and is used to cancel the microwave field at detector 17.

In order to have the canceling microwave field 34 cancel the combined microwave field at detector 17, it is necessary to offset emitter 19 from detector 17 with respect to their relationship to the host platform 13. In particular, detector 17 must be further from host platform 13 in order to receive incident microwave field 30 before canceling microwave 34 is emitted. The exact spacing is a design consideration based upon the dielectric constant of the coating processing speed of amplifier 20, expected radar environment, etc. Separation between detector 17 and emitter 19 in the horizontal and vertical directions of FIGS. and 2 is typically on the order of millimeters.

The advantages of the present invention are numerous. The active radar stealth device provides stealth protection for any host platform regardless of the shape and size of the platform. The present invention adapts to any changing incident microwave fields since each detector/emitter pair functions independently to cancel out the microwave field at that pair. In addition, the design of the present invention could be easily adapted to generate a microwave field at emitter 19 that would modify the detected combination in any fashion. This would provide the added capability of modifying the microwave radiation response of the host platform as desired.

In another aspect of the present invention, the active radar stealth device might be combined with one of the passive/absorptive approaches. The resulting system would consist of two layers, an inner layer being a passive/absorptive material and an outer layer consisting the active radar stealth device of the present invention.

Thus, although the invention has been described relative to specific embodiments thereof, it is not so limited and numerous variations and modifications thereof will be readily apparent to those skilled in the art in light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. What is claimed is:

http://www.freepatentsonline.com/5036323.html

[]'s

[Penguin]

Santiago, Dizem que o Spectra custou quase um terço de tudo o que foi gasto no desenvolvimento do Rafale. O que dá uma idéia de como esses sistemas EW são sofisticados (e caros!).

[]'s

Um EMB-145 custa USD 23mi. Um EMB-145 AEW custa provavelmente mais de USD 100mi.

[]s

[Penguin]

Uma pesquisa no Google, mas é interessante:

Active Radar Cancellation

ACTIVE CANCELLATION

A method of passive cancellation of the reflected radar signalwas already discussed, together with its shortcomings. A far more flexible but also more complex approach is to activelyreplicate the incoming signal and reverse its phase in order toachieve the same effect. Since it involves active emissions,this technique is more appropriately classified as part of theactive jamming effort, but is nevertheless noteworthy withregards to stealth because its net effect is the reduction (or even complete elimination)of the amplitude of the reflectedsignal, and thus the reduction of the targeted object’s apparent RCS.
Just how complicated it is to cancel a reflected radar signalcan be reasoned from the fact that the original incoming signalfrom the radar will be reflected from many spots on theaircraft's body. Each spot will produce an individual reflectionwith its own unique amplitude and phase. The amplitude of the reflection would depend on many factors, such asincidence angle, particular type of material, geometrical formof a certain location on the aircraft's body that produced thereflection and some other factors. The phase shift will bedictated by the wavelength of the radar signal and the location(and geometrical form) of the particular spot that produced thereflection in question. The enemy radar does not, however,receive all of the reflected variations of the original signal asseparate entities. It either selects the strongest return signal, or averages several strongest reflections. This simplification can be used to the advantage of the aircraft, since it will only needtwo antennas to transmit a simulated return signal averagedover the length of the aircraft. The return signal, pickedUp by the radar, would look somewhat chaotic, consisting of background noise and the main return spikes. These spikesare, presumably, the main targets of active cancellation (hereagain we see the importance of first shaping the aircraft tominimize and actively control the formed spikes). It isimportant to understand, however, that in case of a real-world effective system we are dealing with an immenselycomplicated issue. Something that can be popularly explainedwith a single wave sinusoidal signal will becomeprogressively more complex in real-life situations.Active cancellation as a working method places strongemphasis on several things to happen properly:

* The aircraft has to have a system capable of analysing theincoming signal in real-time and replicating itscharacteristics faithfully enough to disguise itself as the“true” signal, before its phase is reversed. Analysing thesignal on first contact is not enough; the enemy is likelyto shift the emission characteristics of the radar equipment within its physical limits (PRF, signalfrequency etc.) throughout the duration of the detection/tracking attempt. Likewise therefore, theanalysis process has to be repeatedly performed as long asthe aircraft remains within the detection envelope of theemitter.

* The phase-reversed signal must be transmitted with justenough power to match the “real” signal reflected back atthe receiver. Careful power management is crucial here; aclever software algorithm in a modern radar system maytry to check the signal strength difference betweenincoming spikes and reject those that seem a bit “toopowerful” for the given situation. The purpose here isdeception, not to flood the other guy’s scope with white-noise static.

* The bearing of the incoming signal must be determinedaccurately so that the “fake” reflection will be reflected atthe original transmitter and nowhere else. This alsoimplies a very accurate laying of the onboard beam-transmitter for the fake signal, as well as rapid beam-steering for circumstances where the airframe’s attitudeand velocity vector is rapidly changing(e.g. whilemanoeuvring to avoid enemy fire). This is easier said thandone: it is hard enough to precisely locate (in bothazimuth and elevation) the emitter in order to point thefake signal only there and nowhere else; let alone keepingthe beam on-target while the aircraft is performinganything from routine subtle navigation courseadjustments to gut-wrenching missile-avoidancemanoeuvres. For this reason, only an electronic-scan arrayis practically suitable for emitting the fake signal.

Despite this tall order of requirements, active cancellation offersseveral advantages compared to more conventional jammingtechniques. Both barrage and deception jamming cannot avoid tipping-off the enemy on “something” going-on; here, however,the element of surprise is fully retained for exploitation. Asignificantly less amount of transmission power is required, onlyenough to replicate the weak energy reflection back to the enemyemitter; thus the overall system can be light and compact enoughto be fitted to aircraft hitherto unable to benefit from the existenceof heavyweight jammers. This also means that other onboardavionics are significantly less hampered by RF-interference whileactive cancellation is in progress (those who recall the EW-avionics interference troubles of aircraft such as the B-1, the EF-111, the Su-27 or the EA-6 will certainly appreciate this).

The Spectra integrate dew suite on the Rafale fighter is a primeexample of active cancellation. All the elements described aboveare in place: sensitive and precise interferometers for passivedetection & localization, powerful signal processors as part of theoverall avionics suite, and conformal electronic-scan arraysdedicated to the transmission of EW signals. Combining a semi-stealthy airframe structure (treated with RAM in significantquantities) with various traditional forms of jamming plus activecancellation can result in an airborne weapons platform of vastlyLower RCS than one would expect from an otherwise “ordinary-looking” canard-delta aircraft.

There have been speculations that the Russians may be using thistechnique on their S-37 Berkut and possibly MiG 1.42 prototypefighters. It is also believed that the ZSR-63 defensive aidsequipment installed on B-2 bombers may be using this technique.It is not clear whether the F-22and F-35 are going to employactive cancellation in their EW arsenal. Certainly the pieces are inplace hardware-wise: An added bonus of the AESA radars fittedon both aircraft is that the operation of multiple RF beams inparallel(as opposed to the single beam of mechanical-scan andpassive electronic-scan systems) enables the radar to scan, track and jam at the same time. It is however unknown if the relevantsoftware is going to be in place to exploit this capability.Certainly the F-22 is more than capable of performing thisfunction with its ultra-sensitive ALR-94 receivers and ampleonboard processing power, in addition to the large AESA set.
Whether the significantly smaller and thus volume/weight-challenged F-35 will be able to perform the function on its ownhardware remains to be seen.

A Seminar Report On Stealth Technology In Aircraft - CSJM University Kampur
http://pt.scribd.com/doc/51581190/2/ACTIVE-CANCELLATION

[]'s

O autor acima cita rumor como se verdade comprovada fosse. Isso não é legal para um trabalho acadêmico (trabalho de um aluno de penúltimo ano de graduação do curso de Engenharia Mecânica de uma Universidade da Malasia).

O que ele descreve em vermelho não é exclusivo do Spectra. Esses elementos tb estão presentes nos demais sistemas de EW dos caças de 4a geração.

Se o Spectra tem ou não a capacidade de Active Radar Cancellation, ainda é algo a ser comprovado ou afirmado pela Thales/Dassault.

Esses rumores tiveram início através da interpretação de Bill Sweetman em uma palestra na qual representante da Dassault mencionou que o Spectra contava com "stealthy jamming modes".

Aqui cabem duas observações. A função do jamming é evitar que o caça seja detectado. Há uma infinidade de métodos, que vão desde saturar a tela do radar adversário, alterar a posição do alvo, inserir alvo(s) falso(s), etc. Algumas inclusive muito discretas ou stealthy.

A tecnologia DRFM (Digital Radio Frequency Memory) presente nos sistemas de EW dos caças de 4G atuais permite coisas bem interessantes:

An example of the application of DRFM in jammers: The DRFM digitizes the received signal and stores a coherent copy in digital memory. As needed, the signal is replicated and retransmitted. Being a coherent representation of the original signal, the transmitting radar will not be able to distinguish it from other legitimate signals it receives and processes as targets. As the signal is stored in memory, it can be used to create false range targets both behind (reactive jamming) and ahead of (predictive jamming) the target intended for protection. Slight variations in frequency can be made to create Doppler (velocity) errors in the victim receiver as well. DRFM can also be used to create distorted phase-fronts at the victim receive antenna which is essential for countering monopulse radar angular measurement techniques.

http://en.wikipedia.org/wiki/Digital_ra ... ncy_memory
http://ftp.rta.nato.int/public//PubFull ... 80-P07.pdf

Outro ponto é que o jamming pode ser feito com precisão, atuando através de emissões bem direcionadas e focadas, evitando chamar a atenção desnecessariamente, a exemplo do Spectra com suas antenas do tipo active phased array na base do canard.

[]s

[Penguin]

PDF muito interessante:

AIRBORNE ELECTRONIC ATTACK
HIGH POWER STANDOFF
AND ESCORT JAMMING
New generation AESA
digital support jamming

http://www.thalesgroup.com/Portfolio/Do ... gType=2057

[Penguin]

Airborne Electronic Attack (AEA)
New Airborne Electronic Attack concept for electronic support jamming missions in present and future environments

Increased ES/EA mission capability through advanced jamming functions

Pod or internally mounted, for fighter aircraft, UAV, J-UCAV or mission aircraft with network centric warfare (NCW) capabilities
Very high power main / side / scattered lobe jamming
Unsigned raid DDA, up to RF horizon action possible
Smart techniques / coherent waveforms / covert jamming
Smart power management using active phased array transmitter


Outstanding performance with latest jamming technologies

Solid-state active phased array AESA jamming
Highly sensitive digital reception
Highly effective multi-bit DRFM jamming techniques


Main features

Very high ERP, for main, side and scattered lobes jamming
Multiple DRFM architecture for simultaneous beam aimed multi-threat jamming
Smart digital jamming techniques
Wide angular coverage, up to 360°
Extended low and high brand threat coverage capabilities


Carbone Demonstration Aircraft

The new Thales AEA concepts and technologies have been implemented within the CARBONE demonstration programme.
CARBONE was presented and evaluated during the MACE X NATO trials, operating against sophisticated eastern/western radar technologies


http://www.thalesgroup.com/Portfolio/De ... /?pid=1568

[AlbertoRJ]

Segundo dizem, o Carbone demonstrou a capacidade de cancelamento ativo lá pros idos de 2000...

Of course, the United States today is just about the only country that can afford scores of dedicated electronic- attack aircraft and the cast of thousands of highly trained experts who support them. "The US has specialized EW aircraft that cover an area and so take some of the burden off the strike aircraft in terms of self- protection." said Dov Granot, business development manager for the Elisra Group (Bene Beraq, Israel). The Israeli Air Force favors a system where select aircraft in a strike package are equipped with escort- jamming pods. "Israel's philosophy is that an aircraft needs to be able to protect itself from start to finish, from take-off through landing."

Jean-Philippe Gourion, deputy director of strategic planning for Thales Airborne Systems (Paris, France), said Thales is working on an escort-jamming concept in which dedicated platforms and crews would be replaced by a combination of integrated systems featuring a solid-state, phased-array jammer with very high transmitted power and real-time multi-beam steering. This would be fitted in an automatic pod carried by a multirole fighter for the stand-in/escort jamming mission. Since 1993, Thales has been developing its Carbone offensive jammer demonstrator under contract to the French military procurement agency. According to Gourion, the Carbone is significantly more powerful than existing or upgraded offensive-jamming pods. Carbone also draws on Thales' digital receivers and real-time geolocation algorithms, such as those implemented in the Spectra EW system for the Rafale aircraft.

The Carbone demonstrator has been mounted on a Mystere 20 testbed aircraft and has flown extensively since 1998, including during the NATO MACE X field trials in August 2000. A preliminary study for a pod installation has been through cost-assessment and risk- reduction studies. "Operational trials have demonstrated Carbone's effectiveness, and particularly its capability to jam through scattered lobes." Gourion said. "This is a big change in the strategy of the use of such equipment."

A fighter aircraft carrying a pod-mounted phased-array jammer would have the ability to loiter at the periphery of the threat area, but not necessarily in line with the flight path of the strikers. Once the strike package is about to enter the threat area the electronic attack aircraft is alerted by datalink to commence jamming through the secondary or scattered lobes of the threat emitters. Thus, the enemy would remain unaware of the direction of the strike package's arrival. Gourion pointed out that there would be some burden during the mission-planning phase to ensure that timing, waypoints, and jamming duration are synchronized. "In fact, if your mission planning is excellent, then you are not obliged to use a datalink or otherwise transmit between the strikers and jammer aircraft," he said.

Another benefit of this approach to stand-in/escort jamming is that the electronic-attack aircraft does not have the same demands on its self-protection jammers, thus eliminating the potential for interference. In fact, Gourion questioned the wisdom of even attempting to operate electronic-attack and self- protection systems on the same aircraft at the same time. "Frankly speaking, I don't think that it would be a very good idea to use stand-in jamming tactics other than those that attack side or scattered lobes at some distance," he said. "If the electronic-attack aircraft is loitering at very low altitude somewhere in a relatively safe place quite close to the danger zone, then you can decide at a given instant to pop up and begin your jamming job."

But if you have to stay in the high- threat area, Gourion continued, it would be much more preferable to use a UAV as a stand-in platform, loitering at very high altitude -- say, over 50,000 feet. The very same selective-reactive technologies that automatically detect, track, and provide the correct jamming response to threats in ICAP III conceivably also make it possible for the EWO to be snug in a command shelter hundreds of miles away, monitoring the proceedings via SATCOM with a cup of coffee. Try that in a cockpit.

To brincando.

[]'s

[Penguin]

Vantagens no uso de antenas emissoras do tipo AESA - active phased array para jamming:

It is unclear what impact this will have on longer term plans which apparently include phased array antennas (much like the B-1 B/ALQ-161) for the jammer transmitters; these will allow time sharing an antenna between several threats without a penalty in power delivered to the threat. Phased arrays allow nearly instantaneous pointing of very tight beams which concentrate more jamming power on the threat. It is almost certain that the EF-111A will undergo the full USAF F-111 A/E offensive avionics/ flight controls upgrade currently under way and proposed for RAAF F-111 s.

http://www.ausairpower.net/TE-Tacjammer.html

[Penguin]

An EA-18G carrying three ALQ-99 jamming pods. The Next Generation Jammer is intended to equip the Growler as well as a number of other platforms. U.S. Navy photo by Jamie Hunter/Aviacom

The Next Generation Jammer and Distributed Electronic Warfare

Written by: Jan Tegler on June 15, 2011

http://www.defensemedianetwork.com/stor ... c-warfare/

[Penguin]

Detection and jamming of LPI radars:

[soultrain]

Vantagens no uso de antenas emissoras do tipo AESA - active phased array para jamming:

It is unclear what impact this will have on longer term plans which apparently include phased array antennas (much like the B-1 B/ALQ-161) for the jammer transmitters; these will allow time sharing an antenna between several threats without a penalty in power delivered to the threat. Phased arrays allow nearly instantaneous pointing of very tight beams which concentrate more jamming power on the threat. It is almost certain that the EF-111A will undergo the full USAF F-111 A/E offensive avionics/ flight controls upgrade currently under way and proposed for RAAF F-111 s.

http://www.ausairpower.net/TE-Tacjammer.html

Os sistema de Guerra electrónica das nossas Vasco da Gama já têm phased array antennas, desde que foram entregues em 1991. Cada sistema custou na altura cerca de 4 milhões, compramos para as 3 VdG e para as 3 João Belo, não foram para o Uruguai.