InstNote the size. you have 1300 modules in roughly 8-12 square meters area.
That said, I redid the calculation and the wavelength from module density falls in the C-band, not the L-band for the proposed J-11 radar; it’s about 5 ghz.
InstFor third generation, read fourth, since the Chinese came to the game late. Fighter implies a target between 1 and 5 m^2, which suggests a practical range between 130 and 200 meters. Other sources suggest the KLJ-7A is on par with the APG-81, which, if you accept it, also suggests unbelievable performance.
As to air-cooling vs water cooling, water cooling is about 24 times more effective at transferring heat energy. This implies that the energy output is neutered by up to 96%. I’d also point out that even American GaAs radars are all liquid-cooled; the vast majority of fighter radars employ liquid-cooling, not air-cooling, due to the high need for heat dissipation.
My point is more that the oddity is that you are getting outrageous range figures, alongside reports of air-cooling, which suggests GaN, which supposedly generates less heat and is more heat tolerant.
As to the L-band, the J-11 radar is an 800 module radar at Flanker size. The math points to an L-band antenna, due to the low module count.
[ATTACH=CONFIG]258508[/ATTACH]
One remaining possibility is that the AESA the Chinese documents are describing is just a prototype AESA. I hear there are rumors, unconfirmed, that the J-11B is receiving AESA, but the J-11D project has been held up for quite some time. It’s easy to publish a research paper, but it’s hard to actually put the design into practice.
About the power estimation, the irbis-E has an effective power output of about 10 kW due to efficiency losses from the PESA design. Assuming the same aperture, you’d need about 55 kW to achieve the stated Chinese claims in their paper. Divided by 800 modules, you’d need a power output of 68 watts peak power per module to achieve the 450 km range vs 0 dBsm.
Inst[ATTACH=CONFIG]258498[/ATTACH]
Compare to APG-79. IMO, you can’t tell; both slatted and tile arrays stuff antennas on the front at the end. I previously thought tile was slightly more compact, but as it turns out, comparing the tiled APG-63v3 and slatted APG-63v2 the difference, if any, must be minuscule.
InstIs that the only claim? I mean, you can’t tell where the 3 m^2 object is, it could be 300, it could be 200, it could be 500 km relative to this graph.
As to the 350 km figure, check this out:
http://www.niip.ru/catalog/aviatsionnoe-naprvlenie/rlsu-irbis/
Insthttps://www.flightglobal.com/FlightPDFArchive/2002/2002%20-%203458.PDF
APG-79 was tiled, and moreover, it was apparently using second-generation tiles.
For general AESA vs PESA, though, I’ve been looking around for sources and I note quite a few state that the APG-77v1 runs 10 watt modules, meaning that the APG-77 is a 20 kW peak power AESA. Given the noise difference between PESA and AESA, the APG-77 should feature about 17% better range than the Irbis-E, however, so AESA, for the same aperture and system size, should be able to achieve better performance than PESA, albeit at significantly greater cost.
One remaining point of interest, though, is the packaging technology on the N036 AESA. Since tiled AESA, while cheaper, has poorer heat dissipation characteristics, an ultra-high performance AESA would prefer to use bricks / slatted arrays, even if it adds to cost and weight. Are the APG-81 and APG-77 running tiled AESA or slatted AESA? Whether they do or do not, does the N036 run tiled AESA or slatted AESA? If the N036 runs tiled AESA, what are the chances that the technology will return to the Su-35, since AESA presents mild performance advantages alongside better EW performance?
Another interesting point about radar engineering is the air-cooled vs liquid-cooled issue. The KLJ-7A proposed for JF-17 upgrades is air-cooled, which is unusual as most high-performance AESA generate enough heat to require liquid cooling. The Chinese, in updating one of their naval ships, moved from air-cooled ESA to liquid-cooled ESA, presumably increasing its performance. Why did the Chinese choose air-cooling for the KLJ-7A? Did they manage to jump to high-performance GaN, and no one knows about it? Or does it suggest the KLJ-7A is deliberately gimped; it claims a 200+ km detection range vs fighters, which is below the scaled performance of the J-11 radar, so it might handle difficulty with X-band GaN manufacture by lowering their power output and sticking to air cooling.
One possibility is that the J-11 radar is already GaN; that would explain why the radar is in the L-band as opposed to the X-band. The calculations based on the projected required power output (55 kW) come out to a roughly 68 watt power output, which is a power rating known to be in the reach of Chinese L-band GaN modules and would explain why the J-11 radar is inexplicably an L-band fighter radar.
InstI’m curious: where did the 400 km Irbis-E figure come from? I note that the official Irbis-E range is 350 km vs 3 m^2, from the manufacturer’s website, yet the 400 km figure gets repeated constantly. What’s the original source here?
Inst@bring_it_on: Kopp discussed the US moving to tiled AESA in the early 90s. It appears it’s the APG-79 that was the first recipient of tiled AESA; the first APG-79s in operational fighters occurred around 2005.
InstOkay, and which radar does this go into? The small scale of the radar makes it look like a missile seeker. It’s possible that similar technology is being used for Phazotron’s Zhuk-AE, which would also explain why the module count increased from 680 to 1016. We also know FGA-29 uses a slat-type antenna; I’m looking for evidence that the FGA-35 runs tiled antennas.
Edit: it looks like the FGA-35(3D) runs tiled antennas, given the weight savings and reduction in bulk. So Russia does possess tiled AESA technology, circa 2012-2013.
InstOkay. But the point still stands, the Americans are first with their engine technology, after which come the various Europeans, then the Russians, then the Chinese. Russian engines aren’t designed for high MTBO (and for that matter, neither are those of the Chinese, given the present state of their engine technology), since the Russians expect attritional warfare, not blitzkrieg.
As to Russian AESA, ever counted the modules on the Zhuk-AE? The first versions had 688 modules (and honestly, the J-10’s AESA is pretty crap as well), whereas the F-22 has around 2000 modules on its AESA and the F-35 achieves a 35% higher module density than the F-22. Likewise, the large scale AESA working in L-band typically have lower module counts than X-band, due to half-wave dipole antenna design (module count is linked to wavelength). This means that surveillance radars and other large-scale AESAs require less modules per square meter, albeit larger modules, than small-scale AESAs. Small-scale AESA, then, presents a miniaturization challenge, in which the challenge is building small components of high yield and reliability. This is a technology problem, not a labor cost problem, and one the Russians have yet to master.
One interesting thing I’ve discovered lately is the use of tiled AESA antenna arrays. This is a novel AESA technology, one that the Chinese demonstrate, the Americans have on hearsay, and the Russians have given no indication. Conventional (first generation) AESA tend to use slat-arrays, i.e, the T/R module is arranged at the same angle as the direction of the radar. Tiled array AESA, on the other hand, stack T/R modules on top of each other. The advantage is that tiled array AESA require less wiring than slat-array radars, reducing cost and weight, but lose heat-dissipation ability, since tiled-array radars are heat-sinked by the array frame as opposed to having individual heatsinks.
An example would be here: the tiled array AESA used in the APG-79 apparently cuts weight by 75%.
https://www.flightglobal.com/news/articles/radars-for-life-158369/
InstGiven that the head designer of the J-20 started with the JF-17, moved up to the J-10B, and ended up designing the J-20, I wouldn’t say the JF-17 was a failure at all. If you see it as a fundamentally Pakistani plane with Chinese design and technology, it was a cheap project that gave Yang Wei his start in aircraft design. Moreover, it gave Chengdu experience in playing with LERXes, without which the J-20 might have been a stealth Eurofighter instead of a stealth long-coupled Rafale. Remember, the Chinese came up with the long-coupled LERX-canard-delta airframe and it was the Europeans that followed, instead of the other way around.
InstLook at the nozzle length; the WS-10 has short nozzles, while the AL-31 has long nozzles.
InstFirst, it’s not my China, second, there’s a difference between fighter-scale AESA, missile-scale AESA, and surveillance-scale AESA. Note the Chinese actually ran AESA on their warships and had AESA radar on their AEW&C aircraft before moving it onto their fighters. The challenge is not so much as building an AESA itself, as it is to miniaturize it cheaply; large AESA can use large modules using older fabrication technologies, but radar using small modules have to use more modern and less mature fabrication technologies.
I’d also like some information on relative PESA cost. For instance, in the case of the F/A-18, the APG-79 upgrades to AESA cost about 3 million a piece. In the case of the F-15, the APG-63v3 costs around 9 million a piece. Can you point to a case of PESA being more expensive than AESA, with the same radar aperture size?
I’d also point to the Russian AESA pods as an example of why Russia has traditionally been unable to build AESA cheaply. If you note what’s going on with GaN, GaN is actually preferred over GaAs if cost were no issue. Yet the main implementations of GaN, in the West, are in surveillance radars and in jamming pods, not in fighter radars, for which the cost is not acceptable.
Inst@Deino: Latenlazy commands a lot of respect on SDF, but here’s the funny thing. Angle measurements and so on are standard for crime scene investigation, and these sorts of tools are already in use. It stands to reason that it’s probable that military intelligence organizations already have EM charts, even if ambiguous accuracy, for the J-20.
Check this field out:
https://en.wikipedia.org/wiki/Photogrammetry
That said, the problem with the stitching is the lack of background frames, that’s to say, it is very difficult to ascertain the relative position in the photograph of the J-20, as well as certify that this isn’t a fabrication built out of multiple, distorted shots, aiming to impress a smaller turn radius than is actual. I suppose with computer processing power, it should be possible to stitch the images together using features like the light fall-off with altitude, but it’s difficult to do by hand.
@Marcellogo: See:
https://forum.keypublishing.com/showthread.php?141042-AESA-VS-PESA-radars&p=2362859#post2362859
2.9 dB less loss (output only) should translate to a 17% increase in detection range.
Insthttps://www.globalsecurity.org/military/world/china/j-11-variants.htm
I can also find a dozen other sources suggesting that Chinese AESA reaches 450+ km detection range (tracking range can be assumed to be 50% of that) vs 0 dBsm. This outranges American figures for their APG-81 and 77, but I’d rather assume the Americans are hiding their actual maximum detection ranges vs 0 dBsm– recall the incident where the Japanese module-counted American AESA and found that they typically had 33% higher module counts than the publicly disclosed figures.
Remember, it’s PESA vs AESA; PESA is much less frequency agile and does not come with an LPI mode. Chinese Flankers can be safely expected to detect Russian Flankers first and fire first. Of course, if the missiles miss or are spoofed, the Chinese are screwed, and actual NEZ for PL-15 is going to be far shorter than the stated maximum range.
InstCan you guys help out here? I need a turn radius and a bank angle for this shot. My rough calcs say between 200 and 274 meters, bank angle is around 80 degrees. This implies a turn rate of 40+ degrees at mach .25.
Sign In
