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    #61
    Err.. the size of the antenna isn't classified. And its entirely independent of the T/R density.
    You forgot that along with Spectra Dassault perfected the Tardis effect for nose cones...

    Comment


      #62
      So where does the official diameter figure comes from ? Dassault ? Thales ? AdA ?

      Comment


        #63
        There are pics of Egyptian Rafale on net. The nose is one of the smallest. Not much different than Gripen/F-16
        Can't believe they can't enlarge nose in 30 years

        Comment


          #64
          It has not prevented the rafale to perform well in technical evaluations and exercises, even against design with biger nose, there is so much more. Gripen/F16/SH size like is ok anyway. In some competing designs, bigger can also hide a lack of sofistication where raw power is to compensate for lack of sensor fusion, integrated avionics etc. Or their massive RCS. The more you radiate the more you become visible also, it can play against you. At that game modern RWR with 3D geo-location must be part of the consideration. It has been almost ten years that rafales display long range BVR passive shots with EW only.
          Last edited by eagle1; 7th February 2018, 22:51.

          Comment


            #65
            Err.. the size of the antenna isn't classified. And its entirely independent of the T/R density.
            It is officially classified, sorry.

            ut let's imagine you have a 10 GHZ frequency , apply lambda/2 "rule" and you will find something very close to 1000 (that should tell you about the exat size)

            Comment


              #66
              Originally posted by halloweene
              It is officially classified, sorry.
              You can 'classify' the diameter of the tyres as well, its not going to prevent people from being able to measure them.

              ut let's imagine you have a 10 GHZ frequency , apply lambda/2 "rule" and you will find something very close to 1000 (that should tell you about the exat size)
              What are you on about? Frequency has nothing to do with the physical size of the antenna (edit: assuming we're talking about an X-band radar).
              Last edited by Vnomad; 7th February 2018, 23:40.

              Comment


                #67
                Frequency has nothing to do with the physical size of the antenna
                It does when it comes to AESA/PESA antennas. In order to be able to steer the beam, then the signal from one T&R needs to "interfere" with the T&R next to it. This requires precise spacing.

                http://www.radartutorial.eu/06.anten...ntenna.en.html
                "The early bird gets the worm but the second mouse gets the cheese."

                Comment


                  #68
                  Originally posted by SpudmanWP
                  It does when it comes to AESA/PESA antennas. In order to be able to steer the beam, then the signal from one T&R needs to "interfere" with the T&R next to it. This requires precise spacing.
                  That impacts the density of the T/R modules. It does not impact the size of the antenna, which will remain a constant until the aircraft undergoes rhinoplasty.

                  Comment


                    #69
                    Originally posted by eagle1
                    Often but not always the case. Let's take Dassault Aviation official words on page 14 of Fox Three n9
                    Still generic statement versus actual photos. Point is, if the number of T/R modules is not classified and they can publish how many T/R modules the radar has, then there is no point for them to go out of their way to make all mock up with the same 838 modules while still fit Rafale nose. By contrast, if they intended to hide the real number of T/R modules then the number on the mock up still more likely to be real than the one they claimed, since it is it more likely they did not expect people to actually count it. Furthermore, Rafale nose is pretty small and the radar is vertical, it is quite unreasonable to assume RBE2 has the same aperture area as APG-79 as superbug nose is bigger and its radar is canted.
                    Originally posted by eagle1
                    Or their massive RCS. The more you radiate the more you become visible also, it can play against you. At that game modern RWR with 3D geo-location must be part of the consideration.
                    In modern battlefield, data share is a given, a squadron of 20-25 aircraft may have 1-2 transmitting while the rest can remain silent and get information through data link, and geolocate by radar still much faster and more accurate, so RWR alone can't cut it.
                    Originally posted by eagle1
                    It has been almost ten years that rafales display long range BVR passive shots with EW only.
                    It was something like 7.8 nm against a Mirage if i recall correctly.
                    Last edited by mig-31bm; 8th February 2018, 00:50.

                    Comment


                      #70
                      That impacts the density of the T/R modules.
                      Exactly.. I think we were basically saying the same thing from both sides.

                      If you know the freq and the size of the nose then the number of T&Rs can be roughly calculated.
                      "The early bird gets the worm but the second mouse gets the cheese."

                      Comment


                        #71
                        Well the antenna size would not be affected by number of T/R modules unless you're using lower frequency. At lower frequency the spacing requirement increase, means larger antenna or lesser number of T/R module that can be accommodated.

                        If one wish to calculate the number of T/R module that could be accommodated in a size/area of antenna, you can use one method in Skolnik's Introduction to Radar System 3rd edition. Which assume 100% "fill factor" (entire face is covered by elements) With following equation :

                        Nt=(4*A*Ef)/Lambda^2

                        Where :
                        Nt=Number of elements
                        A=Antenna Physical Area
                        Ef= This is a "fill efficiency" factor that i added myself as the original equation assume 100% which, does not correspond to real world. Zhuk AE in example has "fill efficiency" of about 64% this is because of the TRM cold plate design or other antenna structure elements, which precludes anymore TRM/Radiator to be packed in the antenna
                        Lambda = Wavelength.

                        I found 55 cm to be reasonable for the RBE-2 Antenna size prob i would use 60 cm. If we assume 3 cm wavelength (10 GHz) and 95% "fill efficiency" The number of TRM will be 1003. Going higher frequency say 12 GHz would allow 1445 modules to be packed.

                        Regarding RBE-2's "censorship" Well i tend to believe that what we are seeing is a demonstrator or early variant which work in same frequency of early RBE-2. The "more than 1000 elements" variant could be in the future or planned.

                        One thing we can establish is that the RBE-2 must operate in high end of X-band. This allow precise ground mapping, GMTI and probably ground target recognition based on ISAR imaging, it can be done in 3.2 cm wavelength or typical X-band fighter radar, but going higher frequency would allow higher resolution.

                        Comment


                          #72
                          Originally posted by stealthflanker
                          I found 55 cm to be reasonable for the RBE-2 Antenna size prob i would use 60 cm. If we assume 3 cm wavelength (10 GHz) and 95% "fill efficiency" The number of TRM will be 1003. Going higher frequency say 12 GHz would allow 1445 modules to be packed.
                          Well the dia. you take is the operative factor. At 60 cm, the max no. of TRMs would be 1000 but at 55 cm that falls to 840 (all else remaining the same).

                          Also, X-band is 8 GHz to 12 Ghz, so wouldn't one normally take the lower end of the spectrum as the limiting case?

                          Comment


                            #73
                            Originally posted by Vnomad
                            Well the dia. you take is the operative factor. At 60 cm, the max no. of TRMs would be 1000 but at 55 cm that falls to 840 (all else remaining the same).

                            Also, X-band is 8 GHz to 12 Ghz, so wouldn't one normally take the lower end of the spectrum as the limiting case?
                            Well if one desire to maximize number of modules with given antenna aperture, higher frequency would be preferred. and i went on 10 GHz just for the sake of assumption and it's quite reasonable for early estimate.

                            and about 10 GHz is just lies in the operating frequency for earlier RBE-2.

                            Click image for larger version

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                            and let's not forget sake of convenience as 3 cm wavelength is a good round number everyone like to crunch.

                            Comment


                              #74
                              Originally posted by stealthflanker
                              Well if one desire to maximize number of modules with given antenna aperture, higher frequency would be preferred. and i went on 10 GHz just for the sake of assumption and it's quite reasonable for early estimate.
                              My point is that if you want to operate your radar across a band of frequencies, the number of T/R modules you'd populate the array with would correspond to the lowest frequency required. Right? For example, wouldn't an antenna with module density ideal for 10 GHz and above suffer distortion at say.. 9 GHz?

                              I would think at least, for a fighter FCR AESA, spanning most of the X-band would be par for the course, even at the cost of a lower net wattage.
                              Last edited by Vnomad; 8th February 2018, 11:26.

                              Comment


                                #75
                                Originally posted by Vnomad
                                My point is that if you want to operate your radar in a band of frequencies, the number of T/R modules you'd populate the array with would correspond to the lowest frequency required. Right? Wouldn't antenna with module density designed for 10 GHz and above suffer distortion at say.. 9 GHz?
                                Yes. While my point is that to be 1000+ TRM RBE 2AA will have to operate not in 9GHz.

                                Comment


                                  #76
                                  Still generic statement versus actual photos. Point is, if the number of T/R modules is not classified and they can publish how many T/R modules the radar has, then there is no point for them to go out of their way to make all mock up with the same 838 modules while still fit Rafale nose. By contrast, if they intended to hide the real number of T/R modules then the number on the mock up still more likely to be real than the one they claimed, since it is it more likely they did not expect people to actually count it. Furthermore, Rafale nose is pretty small and the radar is vertical, it is quite unreasonable to assume RBE2 has the same aperture area as APG-79 as superbug nose is bigger and its radar is canted.
                                  Dassault official statement did not say "close to 1000 modules" or "around 1000 modules" but "more than 1000 modules". Proving your point with a mock up is a dead end, and of course their is a point in hiding the exact number of modules. I don't think you would find the exact/precise number for any manufacturer. SH radar is not that big, you have to fit the gun in SH nose. I was just referring to an interview in the weekly A&C where a Thales project manager told current RBE2 AESA was similar in performance to the APG-79.

                                  In modern battlefield, data share is a given, a squadron of 20-25 aircraft may have 1-2 transmitting while the rest can remain silent and get information through data link, and geolocate by radar still much faster and more accurate, so RWR alone can't cut it.
                                  That's true for NATO forces, less sure for the rest. Anyway, you would have AWACS support in your scenario so what the point. You would get the global picture from a third party.

                                  It was something like 7.8 nm against a Mirage if i recall correctly.
                                  That was a shot in rafale six, but in the frontal emisphere, range is much more important. It is routinely used in exercises with confirmed kills and first report dates from ATLC 2009 in the UAE. From a personnal discussion with a rafale pilot during at a Paris air show, this tactic is usually used for defense but even if the Pk is lower it forces your oponent to break engagement. With the newer version of SPECTRA coming this year, it will be even more accurate and deadly.

                                  From AFM :

                                  The current Thales RBE2 AESA radar
                                  will be further improved. It will benefit
                                  from the introduction of two new air-tosurface
                                  modes: a ground moving target
                                  indicator (GMTI), to detect and track moving
                                  targets over land, and a UHR (ultra high
                                  resolution) mode, to replace the current
                                  HR functionality for synthetic aperture
                                  radar (SAR) imagery, offering superior radar
                                  image quality at very long distances. The
                                  ability to interleave radar modes will be
                                  enhanced, thus helping provide aircrews
                                  with even better situational awareness.
                                  The Spectra electronic warfare/selfprotection
                                  suite produced by Thales and
                                  MBDA is fully integrated. It is composed
                                  of a wide range of systems: a Dtecteur
                                  dAlerte Radar (DAR, or radar warning
                                  receiver), a Dtecteur dAlerte Laser (DAL,
                                  or laser warner), a Dtecteur de Dpart
                                  Missile (DDM or DDM NG, or missile
                                  launch detector), a high-power radar
                                  jammer, and decoy dispensers that can
                                  launch a range of flares and chaff.
                                  Over the coming months, Spectra will
                                  be improved, with bandwidth extensions
                                  for the detectors and jammers to cover
                                  lower and higher frequency bands, thus
                                  providing an instantaneous reaction
                                  against any type of pop-up threat.

                                  Our objective here is to obtain extremely
                                  accurate RF emitter geolocation and 3D
                                  tracking, including of airborne radars, said
                                  the programme director
                                  . The capabilities
                                  of a single Rafale to locate and track a threat
                                  without resorting to traditional, but timeconsuming,
                                  methods of triangulation or of
                                  bearing measurements along the aircrafts
                                  flight path will be significantly improved. It
                                  is a very important step forward, and the
                                  recent progresses made by Spectra will boost
                                  the capabilities of the Rafale in that field.
                                  Also GaN technology and additional emitting panels should sound appealing, not to mention integrated offensive jamming in the radar & emitting panels :

                                  GaN technology
                                  Thales and the DGA are actively preparing
                                  the future radar developments that will be
                                  introduced on Standard F4.2, incorporating
                                  cutting-edge Gallium Nitride (GaN) technology
                                  for the radar and jammer antennas.
                                  Thanks
                                  to additional radar apertures, detection
                                  capabilities will be unmatched and electronic
                                  attack capabilities will become a reality.

                                  The programme director explained: Even though
                                  we are entirely satisfied
                                  with the current RBE2 AESA
                                  radar, we are already working
                                  on the next generation scheduled
                                  to appear on new-build aircraft in 2025.
                                  For the same volume, GaN technology
                                  will offer an expanded bandwidth, more
                                  radiated power and an even easier ability
                                  to switch from one mode to another, or
                                  from one functionality to another. With
                                  the same antenna, we will be capable of
                                  generating combined, interleaved radar,
                                  jamming and electronic warfare modes
                                  as part of an electronic attack mission.
                                  GaN emitters will not be restricted to the
                                  radar and they will also equip the Spectra
                                  suite. For example, for the antennas in
                                  the wing apexes, ahead of the canard
                                  foreplanes, we could obtain a very quick
                                  emission/reception cycle, either saving some
                                  volume or augmenting radiated power.
                                  On Tranche 5 Rafales, we will have at our
                                  disposal twice the amount of transmitted
                                  power for the radar and jamming antennas.

                                  Thales has already produced and tested
                                  in laboratories a series of GaN module
                                  prototypes for the new radar and initial
                                  testing results look extremely promising.
                                  Following the entry into service of the
                                  AESA in 2013, the deliveries of the Meteor
                                  in 2018 will push the Rafale into a class of
                                  its own we will be the only ones in the
                                  world operating a fighter equipped with
                                  an AESA and a ramjet-propelled missile
                                  but we have to keep investing to maintain
                                  our leadership. This is the reason why this
                                  GaN technological path is so important,
                                  especially for the development of additional
                                  emitting panels and apertures that will
                                  offer extended radar angular coverage.
                                  It is not just an improvement; it is a
                                  real technological breakthrough in the
                                  field of detection.
                                  Jamming modes will
                                  not be left untouched and will push the
                                  Rafales electronic warfare capabilities
                                  to unprecedented levels thanks to the

                                  introduction of what we call smart jamming,
                                  with a wider band coverage and GaN
                                  emitters from 2025. These capabilities
                                  will be further expanded thanks to the
                                  adoption of MFAs [Multi-Function Arrays].

                                  The Rafales Front Sector Optronics (FSO)
                                  will be fitted with a new-generation infrared
                                  search and track (IRST) sensor optimised
                                  for the tracking of air targets, either alone,
                                  or in conjunction with the RBE2 radar.
                                  Last edited by eagle1; 8th February 2018, 13:50.

                                  Comment


                                    #77
                                    Well the dia. you take is the operative factor. At 60 cm, the max no. of TRMs would be 1000 but at 55 cm that falls to 840 (all else remaining the same).

                                    Also, X-band is 8 GHz to 12 Ghz, so wouldn't one normally take the lower end of the spectrum as the limiting case?
                                    Well that would be more in line with DSI magazine quoting 1001 modules for RBE2 AESA.

                                    Comment


                                      #78
                                      Taking the opportunity of the current thread here to ask a naive question

                                      All things being equal ( same T/R modules [ characterized by their transmit /receive thresholds ), same T/R spacing/distributions, same total power output avaialble , no cooling issues assumed , Same frequency ...etc ) only assuming no limitation on surface . Increasing the number of module by X% how does that convert into percent increase in detection range ? . Is there any equation out there to compute that ?

                                      While I can see obvious benefits in having more T/R modules : simplier cooling, better power distribution per individual T/R , better agility (more modules to play with ), lesser latency and or interference ( individual T/R submitted to less power so faster at transitionning from transmit to receive mode ...etc ), possibly better range at same power via beam forming on more modules at lesser invidivual power per module compared to more power per individuals on fewer number of modules (would have to be computed though ).
                                      However, I still struggle to put some form of numbers around how increasing the number of modules would "theoritically" translate in radar performance increase when all other things are considered equal .
                                      Am sure they exist ( just by virtue of increasing aperture size ) , but to which extent ? . Is that as simple as a 100% increase translate to 10% or more range increase at same power ,and this indifferently of the individual T/R threshold in Transmit and Receive ?, or is that more subtil to the point that there is for a given power output and T/R characteristics an optimum where the gain to be expected from additional number of T/R modules would be relativelly marginal ?

                                      Comment


                                        #79
                                        MiG-31BM
                                        By contrast, if they intended to hide the real number of T/R modules then the number on the mock up still more likely to be real than the one they claimed, since it is it more likely they did not expect people to actually count it.
                                        I'm sure they knew that people would count. People always count.
                                        Juris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere.
                                        Justinian

                                        Comment


                                          #80
                                          Originally posted by eagle1
                                          SH radar is not that big, you have to fit the gun in SH nose.
                                          The cannon and bell feed are behind the radar, there is a hole leading to front but it has very small diameter because M61 is a 20 mm cannon. Anyway, APG-79 is big because it is canted at around 60, physical T/R modules count give around 1363 modules.

                                          Originally posted by eagle1
                                          I was just referring to an interview in the weekly A&C where a Thales project manager told current RBE2 AESA was similar in performance to the APG-79.
                                          I haven't seen the interview but how can he know how well APG-79 performed? If 2 radar made by the same company then i get his point but APG-79 is made by Raytheon rather than Thales

                                          Originally posted by eagle1
                                          That's true for NATO forces, less sure for the rest. Anyway, you would have AWACS support in your scenario so what the point. You would get the global picture from a third party.
                                          Soviet has datalink since the 80s with Mig-31, iam sure most near peers airforce has datalink by now, and with advanced long range missiles like R-33, R-37, K-100, PL-15, Meteor, AIM-120D then AWACs are very vulnerable.

                                          Comment


                                           

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