AWACS wiht AESA finally beats raptor‘s stealth or not

Anything goes, as long as it is about the Lockheed Martin F-22 Raptor
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mityan

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Unread post06 Jun 2013, 12:16

hornetfinn wrote:I think it's given that future AWACS aircraft will have AESA radars as they offer so much improvement over earlier radar techniques. It can have much superior sensitivity and other characteristics to help against LO and VLO targets.


They dont offer very much improvement. The first point is placing LNA (low noise amplifier) of the receiver much closer to antenna and that gives the improvement of receiver sensivity, several dB, and the second is a new ability to control a magnitude distribution over antenna aperture in addition to phase distribution. The PESA have no this feature. This allows to reduce antenna sidelobes which is good for LPI radar. But the words 'AWACS' and 'LPI' cannot be placed together, this is ridiculous.

But for F-22 AESA is a key point for LPI, that is why APG-77 is AESA. And that is all. For example, PESA N035 Irbis of Su-35 is better than AESA AN/APG-77 of Raptor, but Su-35 is not a stealth so it doesnt need an LPI radar.

I think for detecting Raptor such aicrafts as E-2 Hawkeye is better than E-3 because of its band. One of significant stealth consideration is a cover that absorbs electromagnetic wave. And the thickness of this cover depends on wavelength. So for Hawkeye band of 390-450 MHz (about 2 feet wavelength) the stealth F-22 is not as stealthy as you think, guys.

I dont know about all russian AEW&C aircrafts but A-50 for example uses the same band as E-3 - about 3 GHz. In this band F-22 is more stealthy.

The USA offers AEW&C aircrafts with AESA for sale (Boeing 737) but for their own E-3 they use PESA. Why? I think it is expensive and have no proven benefits.
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hornetfinn

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Unread post06 Jun 2013, 13:44

mityan wrote:
hornetfinn wrote:I think it's given that future AWACS aircraft will have AESA radars as they offer so much improvement over earlier radar techniques. It can have much superior sensitivity and other characteristics to help against LO and VLO targets.


They dont offer very much improvement. The first point is placing LNA (low noise amplifier) of the receiver much closer to antenna and that gives the improvement of receiver sensivity, several dB, and the second is a new ability to control a magnitude distribution over antenna aperture in addition to phase distribution. The PESA have no this feature. This allows to reduce antenna sidelobes which is good for LPI radar. But the words 'AWACS' and 'LPI' cannot be placed together, this is ridiculous.


You just described some of the advantages of AESA array compared to PESA. LPI is just one of those advantages and actually a byproduct of several antenna features. I also disagree that LPI is not useful for AWACS aircraft. While not critical as for F-22 or F-35, it would be helpful if you make your enemy work harder by not being easy to detect and track passively. Other features that make AESA better technology even for AWACS than anything else are;

- improved range due to higher sensitivity and better control of radar beam
- more detected and tracked targets
- better detection capability against LO and VLO targets like cruise missiles
- better jamming resistance due to wider bandwidth, better beam control and ability to use multiple frequencies at once
- lower maintenance requirements
- higher availability due to better reliability and failure resistance (no single point of failure)
- could be used as ELINT system at the same time
- could be used as high speed datalinks as demonstrated by F-22 and F-35
- could be used as EW system as demonstrated by F-22 and F-35
- easier to make aerodynamic, thus improving range

mityan wrote:But for F-22 AESA is a key point for LPI, that is why APG-77 is AESA. And that is all. For example, PESA N035 Irbis of Su-35 is better than AESA AN/APG-77 of Raptor, but Su-35 is not a stealth so it doesnt need an LPI radar.


How is Irbis radar better than AN/APG-77?

mityan wrote:I think for detecting Raptor such aicrafts as E-2 Hawkeye is better than E-3 because of its band. One of significant stealth consideration is a cover that absorbs electromagnetic wave. And the thickness of this cover depends on wavelength. So for Hawkeye band of 390-450 MHz (about 2 feet wavelength) the stealth F-22 is not as stealthy as you think, guys.

I dont know about all russian AEW&C aircrafts but A-50 for example uses the same band as E-3 - about 3 GHz. In this band F-22 is more stealthy.

The USA offers AEW&C aircrafts with AESA for sale (Boeing 737) but for their own E-3 they use PESA. Why? I think it is expensive and have no proven benefits.


Radar absorbing covering is only part of the stealth technology. Besides, it has been proven in public studies that it's possible to do quite thin covers to absorb even the low frequency radar waves.
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hornetfinn

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Unread post06 Jun 2013, 14:02

mityan wrote:The USA offers AEW&C aircrafts with AESA for sale (Boeing 737) but for their own E-3 they use PESA. Why? I think it is expensive and have no proven benefits.


I forgot to address this. USA uses E-3 because that is what they developed in the 70's well before AESA radars became available and that's what they still use because it will be very expensive to change them. Besides there is no real threat that warrants the cost of acquiring them now or in the near future. E-3 is still good enough, but when it will be replaced, the replacement will definitely have AESA radar.
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Unread post06 Jun 2013, 14:51

billsnavycareer wrote:
Lightndattic wrote:If the F-22 is operating in EMCON, how will the AWACS know where to concentrate it's beam? That's like trying to skan the sky for a distant aircraft using 200x binoculars. There's a tiny chance you'll see them, but otherwise you're scanning such a small amount of sky that it's counterproductive.
some experts guessed that the stealth capability of the raptor doesn't deal with metric wave radars effectively?due to most surveillance radars designed to use millimeter wave.While in common sense?metric wave radars do not have the ability to gain the stealthy tango’s precision location but can tell the general direction and range with error of 2 km?Such systems r usually ground-based?
Using DL connection, AWACS share the information and know where to watch.


So basicaly, using IRST, LDAR, bistatic systems etc. combined would increase the chances of detecting and attacking a stealth fighter. But all the above would require a highly advanced integrated air defence system. So the bottem line is: There is no quick fix against stealth.
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Unread post06 Jun 2013, 14:57

thegroundeffect wrote:So the bottem line is: There is no quick fix against stealth.

And there is no urgent job for it.
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Unread post06 Jun 2013, 14:57

hornetfinn wrote:E-3 is still good enough, but when it will be replaced, the replacement will definitely have AESA radar.


It makes sense, I agree.
But how you think it will look like? Still like mushroom, rotating? Or like Saab S-100 for example?
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Unread post06 Jun 2013, 15:17

How is Irbis radar better than AN/APG-77?

Its detection capabilities:
0.01 square meter rcs target - at 90 km range
1 sq.m. - at 300 km
3 sq.m. - at 400 km.

The frequency band and peak/average power are the same as those of APG-77
Because of same freq band and comparable physical dimensions the antenna gains are almost identical.

Then refer to ITU-R P.525 document
The channel loss for radar system is estimated by the following formula:
103.4 + 20*log10(f, MHz) + 40*log10( d, km) - 10*log10(rcs)
So channel loss for 10 GHz and 0.01/90 and 1/300 and 3/400 will be about 283 dB.

For APG-77 range 193 km for target rcs=1 sq.m. So the loss is 275 dB.
Nevetheless AESA should have a more sensitive receiver (because of reason i posted earlier), PESA Irbis has an 8 dB advantage in channel budget. How they achieved it? Only God knows.
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Unread post06 Jun 2013, 22:21

To compare an E-2 or E-3 from the 70s with a currently fielded one is misguided at best. The avionics has been upgraded several times, and the E-2D has AESA dish. It still rotates like the old version, but can steer the beam somewhat.

Quoting detection ranges from unclassified sources, is misguided at best. As I understand it, the latest Irbis-E radar could have the AESA output and receiver sensitivity to put it ahead of the APG-77. What the Irbis-E lacks is the DSP capability to process the return signals to the same level of performance, which is both a hardware and a software limitation. What this means is that a 0.1m2 target at 100nm range might be detectable with a Irbis-E, but at that range, the return would be noisy and subject to false returns as well. This would make it impractical to fire missiles at false returns in an actual combat engagement.The APG-77 has been known to reliably detect clean F/A-18Fs out of China Lake at 100nm range. Without tanks, pylons etc. The F/A-18F has a RCS of about 0.1m2 in clean configuration.
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Unread post07 Jun 2013, 02:24

LPI radar would also make possible a LO AWACS platform -- like a variant of the LRS-B.
Einstein got it backward: one cannot prevent a war without preparing for it.

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Unread post07 Jun 2013, 07:49

mityan wrote: But for F-22 AESA is a key point for LPI, that is why APG-77 is AESA. And that is all. For example, PESA N035 Irbis of Su-35 is better than AESA AN/APG-77 of Raptor, but Su-35 is not a stealth so it doesnt need an LPI radar.



Better in what way? It's(Irbis) not better in range, resolution, speed of scanning, jam resistance, sensitivity, LPI, ESM, EA, simultaneous A/A and A/G, SAR, etc....

For range claims, bear in mind, that the Russian figures for ranges, use a much lower probability(i.e. 50%), than US radars. Secondly, the 400km range (along with the others) claim is for a narrow beam, low search volume scan, not the full azimuth/elevation. Secondly, the US puts out pretty vanilla figures, with regards to detection/tracking ranges. In summary, if you hold the Russian radar to the same detection probability standards (i.e. in the 85-90+ % range), the imagined superiorty evaporates.
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Unread post07 Jun 2013, 09:33

mityan wrote:How is Irbis radar better than AN/APG-77?

Its detection capabilities:
0.01 square meter rcs target - at 90 km range
1 sq.m. - at 300 km
3 sq.m. - at 400 km.

The frequency band and peak/average power are the same as those of APG-77
Because of same freq band and comparable physical dimensions the antenna gains are almost identical.

Then refer to ITU-R P.525 document
The channel loss for radar system is estimated by the following formula:
103.4 + 20*log10(f, MHz) + 40*log10( d, km) - 10*log10(rcs)
So channel loss for 10 GHz and 0.01/90 and 1/300 and 3/400 will be about 283 dB.

For APG-77 range 193 km for target rcs=1 sq.m. So the loss is 275 dB.
Nevetheless AESA should have a more sensitive receiver (because of reason i posted earlier), PESA Irbis has an 8 dB advantage in channel budget. How they achieved it? Only God knows.


The problem here is that you are comparing apples to oranges. Those range figures are in no way comparable directly even though it's very common mistake done.

The quoted detection ranges for Irbis are with only 50 percent detection probability within a relatively narrow cone in front of the aircraft in a special long range detection mode as stated earlier by the radar manufacturer. This means the actual tracking range is about half of that in the best case within that narrow cone or even less in full volume search.

The unofficially stated (by whom is very unclear) 193 km range for AN/APG-77 is said to be typical operating range meaning it's most likely tracking range in TWS or RWS mode. A detection range with similar probability of detection in similar small cone against 3 sq.m target could be better than 500 km if those assumptions are correct. Of course that range is rather useless as it's in Irbis-E.

How do you know what the peak and average power of AN/APG-77 are?

Why are Tikhomirov NIIP actively developing AESA radars if PESA Irbis-E was that great radar and AESA technology offered no major advantages? AESA technology does have many advantages, especially the developmental potential is way bigger than in any other technology.

I find it very unlikely that Russians managed to overcome and even reverse with other means the very significant antenna sensitivity advantage of AN/APG-77 AESA array. It's also very likely that AN/APG-77 has vastly superior signal processing capabilities as USA is definitely the world leader in DSP development and manufacturing.

Basically what I'm saying those very long range figures of Irbis-E are totally irrelevant in real world and only tell us that the radar has rather long range capabilities. In real world it will still have a very long range against non-VLO targets and it's definitely a capable system. However in comparison to AESA radars it won't have LPI capability and won't have nearly similar multitasking capabilities or ECM resistance. AESA radars also have better clutter attenuation figures, so they work better if clutter is present. AESA radars will also have improved reliability and lower maintenance requirements. Irbis-E is definitely a capable radar system, but I find it very unlikely to equal or even exceed the capabilities of AN/APG-77 with rather inferior technology.
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Unread post07 Jun 2013, 11:36

neurotech wrote:E-2D has AESA dish. It still rotates like the old version, but can steer the beam somewhat.

Its PESA is steering already for years.

neurotech wrote:What the Irbis-E lacks is the DSP capability to process the return signals to the same level of performance, which is both a hardware and a software limitation. What this means is that a 0.1m2 target at 100nm range might be detectable with a Irbis-E, but at that range, the return would be noisy and subject to false returns as well. This would make it impractical to fire missiles at false returns in an actual combat engagement

Sorry I dont understand that. What noisy return? You mean chaff, reflection from ground? The proper doppler processing is implemented also in PESA Irbis. What about a future AESA version of this radar for PAK-FA, there is no info in web.
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Unread post07 Jun 2013, 11:44

wrightwing wrote:For range claims, bear in mind, that the Russian figures for ranges, use a much lower probability(i.e. 50%), than US radars. Secondly, the 400km range (along with the others) claim is for a narrow beam, low search volume scan, not the full azimuth/elevation. Secondly, the US puts out pretty vanilla figures, with regards to detection/tracking ranges. In summary, if you hold the Russian radar to the same detection probability standards (i.e. in the 85-90+ % range), the imagined superiorty evaporates.


Never heard about 50% of probability, they assume 90, I think.
Sector in azimuth is +/- 60, but in elevation it is limited to about 10 degrees by a common sense. If you look down at greater angle the point at 400 km will be deep underground. If you look up - high in outer space where no aircrafts can fly. This is true for APG-77. I'm sure.
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Unread post07 Jun 2013, 12:25

hornetfinn wrote:How do you know what the peak and average power of AN/APG-77 are?

Why are Tikhomirov NIIP actively developing AESA radars if PESA Irbis-E was that great radar and AESA technology offered no major advantages? AESA technology does have many advantages, especially the developmental potential is way bigger than in any other technology.

I find it very unlikely that Russians managed to overcome and even reverse with other means the very significant antenna sensitivity advantage of AN/APG-77 AESA array. It's also very likely that AN/APG-77 has vastly superior signal processing capabilities as USA is definitely the world leader in DSP development and manufacturing.


APG-77 consists of 1500 transiever modules with about 10 Watt peak power each. The quasi-continuous operation mode (high PRF) gives average power about 3-4 kW.

I compared just detection ranges and show that Irbis better in this parameter. Of cause this cannot be true in other features.
The key point is that developers of APG and Irbis assume a little different combat tasks, tactics etc. so the come to conclusion to implement one detection range or another.
Maybe because of real future missions requirements (assuming all support) Raptor doesnt need longer ranges.
Another point. The detection capabilities are based on signal energy. As you know energy is multiplication of power and time. Time may be a point that based on true enemy's RWR capabilities retrieved by intelligence (SPO-15 Birch for example). So the developers of APG could sacrifice detection ranges in a name of staying undetectable. So they reduced time on target for the beam.

The AESA is better in following: the ability of smart control of signal magnitude distribution over antenna aperture allows to reduce antenna sidelobes, so it is harder task for ELINT to detect them.
The second is ability to operate on multiple frequencies simultaneously (but I dont know the benefits).
The other modes such as several beams, TWS, mapping, synthetic aperture both implementable in AESA and PESA.
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Unread post07 Jun 2013, 12:50

hornetfinn wrote:as USA is definitely the world leader in DSP development and manufacturing


By the way, I agree if it is related to commercial electronics. But in military... Where there is not enough computational resources.
For example, Raptor has 2 CIP - commom integrated processors, which consist of 66 i960 processors. Their total is evaluated about 20 GFLOPS which is less than single chip produced by russian (!!!) industry - http://en.wikipedia.org/wiki/Elbrus-2C%2B
The Irbis developed later so we may suggest that it can have comparable power.
Also the lag in DSP power may be compensated by algorithms.
For example SAM system SA-5 Gammon has 4kwords ROM and 256 bytes RAM worked on frequency of 64 kHz.
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