AESA elements counting by Japanese(so terrible)

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taog

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Unread post10 Jan 2014, 13:54

APG80 before data:~1000 elements
counting:1020 elements
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APG79 before:~1100
counting:1368
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APG81 before:1200+
counting:1676
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APG77 before data:~2000 elements
counting:1956 elements
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munny

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Unread post10 Jan 2014, 15:18

Nice job.

Think I've worked out why they use the protruding antennas. Cooling is possibly one benefit (heatsink style). With phased arrays, as the beam is slewed off to the side, its gain decreases (due to decrease in projected aperture area) and beam width increases (due to decreased projected aperture width), impacting range and resolution.

With this arrangement, effective aperture area doesn't decrease as much as with flat antennas (example below)

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taog

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Unread post10 Jan 2014, 15:53

munny wrote:Nice job.

Think I've worked out why they use the protruding antennas. Cooling is possibly one benefit (heatsink style). With phased arrays, as the beam is slewed off to the side, its gain decreases (due to decrease in projected aperture area) and beam width increases (due to decreased projected aperture width), impacting range and resolution.

With this arrangement, effective aperture area doesn't decrease as much as with flat antennas.

I think cooling is the most important reason that they use this way
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disconnectedradical

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Unread post11 Jan 2014, 11:48

Another picture of the AN/APG-77, from NG.

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taog

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Unread post11 Jan 2014, 15:40

disconnectedradical wrote:Another picture of the AN/APG-77, from NG.

Don't you surprise that APG-81's amount elements ?
it look the before "+" mean ~400 units (1200+)
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popcorn

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Unread post11 Jan 2014, 18:02

taog wrote:
disconnectedradical wrote:Another picture of the AN/APG-77, from NG.

Don't you surprise that APG-81's amount elements ?
it look the before "+" mean ~400 units (1200+)

Yes, indeed. Any confirmed info for non-US designs?
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taog

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Unread post11 Jan 2014, 19:06

popcorn wrote:
taog wrote:
disconnectedradical wrote:Another picture of the AN/APG-77, from NG.

Don't you surprise that APG-81's amount elements ?
it look the before "+" mean ~400 units (1200+)

Yes, indeed. Any confirmed info for non-US designs?

Russia,Zhuk AE FGA29 reported for having 680 (4 channel) elements,each element has about 5 watt output(peak), tota:3.4 kw peak and 0.85kw average power(25% duty cycle),said to have 130km detecting range for RCS=3 target
repoerted:680 counting:680
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Zhuk FGA35 reported for having 1000~1100 elements,counting by eye :1016 elements
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popcorn

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Unread post12 Jan 2014, 03:09

Thanks Taog.. looking forward to the counts for,Rafale, Typhoon,and Gripen equivalents.
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Unread post13 Jan 2014, 08:21

taog wrote:don't you surprise that APG-81's amount elements ?
it look the before "+" mean ~400 units (1200+)


Not really as the technology level would also affect the element count (besides antenna area). Mid-late 1990's it was possible to put about high-power 2500 X-band T/R modules to a square meter. Currently it's possible to squeeze about 4000 high-power modules to a square meter, especially GaN modules. In the future the amount of modules is likely to increase as the T/R module size is decreasing with the use of GaN and better design and production methods (of both modules and overall antenna).

I think the pictures and the module count might well be accurate. APG-81 module count would be consistent with the approximate size of the antenna and current generation high-end T/R modules available. APG-77 module count would be consistent with it's antenna size and previous generation T/R modules. With current generation T/R modules it should be able to squeeze about 2500 modules to it.

I think APG-81 is way more capable radar than most people realize. Given the amount of modules, it could easily have way higher max output power than even the vaunted Irbis-E as that would require using only 12W T/R modules, which would be far from state-of-the-art. Currently there are up to 20W modules available in GaAs and GaN modules can have way more power than that (over 50W in X-band). It would not be impossible to have something like 40 kW of max output power. On the other hand the high number of T/R modules would make the radar very flexible and be capable of large number of simultaneous beams.
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Unread post25 Feb 2014, 13:23

I've done some calculations about the potential capabilities of APG-81 in relation to raw detection range. If we assume that the pictures of APG-81 T/R module count are correct (well over 1600 modules) and if we assume it uses the best publicly known and marketed GaAs T/R modules (about 16W), we get some impressive numbers. We have to remember that it could well use even more powerful modules as they are available. 25W modules are sold already and even more powerful ones are in development. Even with 10W modules (that became available more than 15 years ago), it'd be very powerful radar set.

With 1676 modules and 10 W power each, giving almost 17 kW peak power with 700 mm antenna diameter (assumed to be perfectly circular), I've calculated that the conservative maximum detection range estimate would be about 360 km or almost 200 nmi against 3 m^2 target. With 16W modules this increase to slightly over 400 km. If the antenna area is larger, then it would give somewhat better range. 800 mm diameter would give about 450 km range with 16W modules. If we calculate the upper boundary of detection with 1676 16W modules and 800 mm diameter antenna with current tech LNA (low noise amplifier) used in receiving path, we get maximum detection range of about 550 km. So we get detection range of 360-550 km for 3 m^2 RCS target depending on antenna diameter and T/R module power and losses. Against 0.1 m^2 target detection range would be between 160 and 240 km. Against 0.001 target it would be between 50 and 75 km.

All these are of course using only single very high power radar beam to search for long range targets within a limited search area or areas without any restrictions. Using multiple beams or using very wide search area or using LPI waveforms is likely to shorten the detection range. But it could still theoretically search for the whole radar field of regard to 250-400 km range depending on exact performance figures and scan time.

All in all this shows very much that the APG-81 is likely going to be extremely powerful and versatile radar set. In air to air combat, it's very likely it's going to see other fighters well before they can see it. It can detect latest 4th generation fighters with reduced signatures (like EF Typhoon, Dassault Rafale or SH) at significant ranges (about 200 km away) even when they are almost clean. Those 4+ generation fighters would be able to detect F-35 at significantly shorter ranges, 50 km or less even with very good AESA radars. That alone gives F-35 (and F-22) a huge advantage in aerial combat.
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sprstdlyscottsmn

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Unread post26 Feb 2014, 06:17

hot dang! Those ARE some good numbers! So at a minimum it is nearly as strong as the Irbis E, and possibly much much stronger.
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Unread post26 Feb 2014, 08:16

sprstdlyscottsmn wrote:hot dang! Those ARE some good numbers! So at a minimum it is nearly as strong as the Irbis E, and possibly much much stronger.


Yes that is right. Actually it's likely being much better than Irbis-E as Irbis-E gets the very long detection range by limiting the search area to 100 square degrees (like 20x5 degree area). This gives it the ability to spend a lot of time searching for targets in that very limited area. Normally PESA and MSA fighter radars have the search area (for tracking) of about 300-500 square degrees. For example in earlier and less powerful Bars radar the search area is 300 square degrees and it can then detect 5 m^2 target 140 km away. Most likely Irbis-E normally scans similar area but with much lower detection range (around 200-250 km). AESA fighter radars can easily change all this and have search areas of several thousand square degrees while still being able to track large number of targets. This means advanced AESA fighter radars will have vastly superior range and search area giving much improved idea what's going on in the sky. Problem for AESA radars seem to be that they require a lot of software to make them work well and also a lot of computing power to handle the massive amount of information they provide (and run their software).

Similarly I'd expect the AESA for PAK-FA offer much improved capabilities to Irbis-E radar, even though it will most likely have lower T/R module count and lower power than APG-81. For example if Russians use the same modules they use for Zhuk-AE (not likely), then the PAK-FA radar should be able to detect 3 m^2 target at somewhat longer ranges than current Irbis-E (using similar search areas), even though it would be significantly lower powered system. This is because AESA radars have much lower transmission and receive losses than MSA or PESA radars. Theoretically AESA radar can be 5-6 times less powerful with the same antenna area to have equal range performance to MSA or PESA radar. Or it can have about 50-60 percent longer range with equal power and antenna size. This is one reason why AESA radars are coming so strongly at the moment.
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sprstdlyscottsmn

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Unread post26 Feb 2014, 16:42

hornetfinn, just to get this all straight in my head, you work with AESA radars professionally correct?
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Unread post27 Feb 2014, 08:24

sprstdlyscottsmn wrote:hornetfinn, just to get this all straight in my head, you work with AESA radars professionally correct?


I used to work with radars (different surveillance radars and fire control radars) and especially been involved in developing radar simulators. Those radars were mostly mechanically scanned ones, but I have some professional experience with PESA and AESA surveillance radars also. I have no experience with fighter aircraft AESA (or PESA) radars and there probably is a lot of things and issues in them that I don't know. Still the radar theory is pretty much the same and I'm quite sure the figures are in the right ballpark. For example all the published figures for AESA radars comply well with radar theory.

The greatest differences in AESA radars come from T/R module count, their power ratings (peak and average power) and all the transmit/receive/signal processing losses. These can affect the real world numbers quite a bit and we do not know the real values for APG-81 or most other fighter radars.
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Unread post27 Feb 2014, 22:08

Thanks for the info.
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