Rafale 2018 Thread: Europe's best Eurocanard

Member for

8 years 10 months

Posts: 1,120

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

Member for

8 years 4 months

Posts: 4,731

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

Member for

8 years 10 months

Posts: 1,120

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.

Member for

7 years 10 months

Posts: 4,168

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)

Profile picture for user Vnomad

Member for

8 years 6 months

Posts: 2,661

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).
Profile picture for user Vnomad

Member for

8 years 6 months

Posts: 2,661

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.

Member for

6 years 1 month

Posts: 2,014

Often but not always the case. Let's take Dassault Aviation official words on page 14 of Fox Three n°9

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.
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.
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.
Profile picture for user SpudmanWP

Member for

10 years 11 months

Posts: 5,198

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.

Member for

4 years 3 months

Posts: 905

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.

Profile picture for user Vnomad

Member for

8 years 6 months

Posts: 2,661

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?

Member for

4 years 3 months

Posts: 905


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.

[ATTACH=CONFIG]258802[/ATTACH]

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

Attachments
Profile picture for user Vnomad

Member for

8 years 6 months

Posts: 2,661

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.

Member for

4 years 3 months

Posts: 905

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.

Member for

8 years 10 months

Posts: 1,120

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 Détecteur
d’Alerte Radar (DAR, or radar warning
receiver), a Détecteur d’Alerte Laser (DAL,
or laser warner), a Détecteur de Départ
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 aircraft’s
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
Rafale’s 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 Rafale’s 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.

Member for

8 years 10 months

Posts: 1,120

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.

Member for

7 years 10 months

Posts: 255

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 ?

Profile picture for user swerve

Member for

14 years 6 months

Posts: 13,433

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.

Member for

6 years 1 month

Posts: 2,014


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.

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

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.

Member for

6 years 1 month

Posts: 2,014

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

Can you post these reports? Iam interested

With the newer version of SPECTRA coming this year, it will be even more accurate and deadly.
From AFM Also GaN technology and additional emitting panels should sound appealing, not to mention integrated offensive jamming in the radar & emitting panels

Those are for F4 standard still in development and introducing in 2023-2025 time frame from what i can remember.