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All Things Stealth


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#1481 Stuart Galbraith

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Posted 12 June 2019 - 0926 AM

 

AFAIK China has had OTH radars for over a decade. I believe they used both surface wave and ionosphere bounce systems. Not sure what makes this system unique. As noted, it works as an early detection system in peacetime but would be unlikely to survive any conflict that escalated to the point of air strikes on the mainland. I also wonder how effective it would be in the relatively crowded skies of the region - minimally you'd have to cross check any target detection against regular air traffic to exclude targets that were merely civilian liners. Such a radar will not give you a hard count of the number of targets if they are close together; a flight of four fighters or pair of bombers would likely look identical to a 777.

The novelty is using SIAR.

'A major shortcoming that’s been overcome is that old HFSWR can only tell an object’s general direction and not its precise location. Wei Dongxu, a Beijing-based military analyst, told the Global Times they overcame that “by designing the world's first practical meter wave sparse array synthetic impulse and aperture radar.” In effect, it uses a bunch of HFSWR systems to triangulate where the object is.'

See here too: https://www.research...ture_processing

 

 

Is it utilizing backscatter to determine where the objects are? I COULD believe that. It would probably work better on an F117 series aircraft than a B2 or F35, but still. In the kingdom of the blind and all that..


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#1482 KV7

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Posted 12 June 2019 - 0939 AM

 

 

AFAIK China has had OTH radars for over a decade. I believe they used both surface wave and ionosphere bounce systems. Not sure what makes this system unique. As noted, it works as an early detection system in peacetime but would be unlikely to survive any conflict that escalated to the point of air strikes on the mainland. I also wonder how effective it would be in the relatively crowded skies of the region - minimally you'd have to cross check any target detection against regular air traffic to exclude targets that were merely civilian liners. Such a radar will not give you a hard count of the number of targets if they are close together; a flight of four fighters or pair of bombers would likely look identical to a 777.

The novelty is using SIAR.

'A major shortcoming that’s been overcome is that old HFSWR can only tell an object’s general direction and not its precise location. Wei Dongxu, a Beijing-based military analyst, told the Global Times they overcame that “by designing the world's first practical meter wave sparse array synthetic impulse and aperture radar.” In effect, it uses a bunch of HFSWR systems to triangulate where the object is.'

See here too: https://www.research...ture_processing

 

 

Is it utilizing backscatter to determine where the objects are? I COULD believe that. It would probably work better on an F117 series aircraft than a B2 or F35, but still. In the kingdom of the blind and all that..

 

'The traditional HFSWR generally works in a monostatic
mode. By applying the SIAP to HFSWR, we propose a
novel HFSWR, which uses multiple omnidirectional transmit
antennae to transmit FMICWs with different carrier
frequencies, namely, the transmitted signals are orthogonal
to each other. The target echoed signal is received and processed
by one or multiple reception antennae. In theory, the
directional transmit antenna array beam pattern can be
formed by proper processing of the received signals. In
addition, the external interference can be suppressed via
adaptive beamforming based on a reception antenna array.
The system construction of the proposed HFSWR is flexible,
it can operate in monostatic, bistatic or multistatic
mode, and the reception antenna can be installed on
ground, ground vehicles or other moving platforms. In
addition to the advantages of the conventional HFSWR
and SIAR, as mentioned earlier, the HFSWR proposed in
this paper also has the advantages of good electronic
counter-countermeasures (ECCM) performance, high
agility and manoeuvrability and good survivability.'
 


Edited by KV7, 12 June 2019 - 0940 AM.

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#1483 glenn239

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Posted 12 June 2019 - 0950 AM

I was wondering what 5G technology would be doing for air defense systems...


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#1484 Stuart Galbraith

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Posted 12 June 2019 - 0951 AM

Im not really very good with technospeak, but to me, that sounds like they built something similar to something I was discussing with someone in 1989, just as the F117 and B2 were being revealed. That you have multiple antenna's to couple up hits from a single (or multple) radars, and use an algorithm to assemble tracking data. Am I reading that right, or am I projecting?

 

Now all they have to do is build enough of them, and figure out how to transmit the data to be useable to engaging systems. Because its still not going to be a walk in the park finding them and engaging them with conventional radar systems. Maybe if they had something comparable to the F35's data handling system....

 

Hum.


Edited by Stuart Galbraith, 12 June 2019 - 0952 AM.

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#1485 Josh

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Posted 12 June 2019 - 1433 PM

It seems like it is a surface wave (diffraction principle OTH radar, not ionosphere bounce) that uses multiple phased array sources and computer processing to overcome at least some of the ambiguities of the long wavelength. The article seems to indicate that the system is somewhat dependent on the geometry of the antenna placement.


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#1486 KV7

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Posted 13 June 2019 - 0512 AM

It seems like it is a surface wave (diffraction principle OTH radar, not ionosphere bounce) that uses multiple phased array sources and computer processing to overcome at least some of the ambiguities of the long wavelength. The article seems to indicate that the system is somewhat dependent on the geometry of the antenna placement.

Correct. See also:

Work on sidelobe suppression - https://ieeexplore.i...ocument/6159611

Work on increased resolution - https://ieeexplore.i...ocument/4697623

A whole book on the subject: https://www.wiley.co...p-9781118609552



 


Edited by KV7, 13 June 2019 - 0512 AM.

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#1487 Stuart Galbraith

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Posted 13 June 2019 - 0519 AM

Ive been trying to read up on radar properties from books on Archive.org, but for them it seems radar development ended in the mid 1960's. :(


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#1488 KV7

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Posted 13 June 2019 - 0828 AM

y1hdHaT.jpg

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GZqnIuW.png


Edited by KV7, 13 June 2019 - 0953 AM.

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#1489 Stuart Galbraith

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Posted 13 June 2019 - 0832 AM

This is all great stuff, thanks for sharing. :)


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#1490 KV7

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Posted 13 June 2019 - 0953 AM

pclTacM.png

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rMQOExm.png
 


Edited by KV7, 15 June 2019 - 0150 AM.

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#1491 glenn239

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Posted 14 June 2019 - 1102 AM

Interesting outline.  The fact that radar pulses are encoded uniquely is not a surprise - figured that.  Also, that the network is big, durable, and cheap.  But, the elimination of the sidelobe is interesting.  Also, that it overcomes the low signal return using a longer length of time to gather signal.  Never saw that coming.  All in all, it looks like the result of massive data transfer rates inherent to 5G tech.  


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#1492 JasonJ

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Posted 18 June 2019 - 1010 AM

newstealth.jpg


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#1493 Nobu

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Posted 18 June 2019 - 2154 PM

Interesting outline.  The fact that radar pulses are encoded uniquely is not a surprise - figured that.  Also, that the network is big, durable, and cheap.  But, the elimination of the sidelobe is interesting.  Also, that it overcomes the low signal return using a longer length of time to gather signal.  Never saw that coming.  All in all, it looks like the result of massive data transfer rates inherent to 5G tech.

I hope that isn’t classified.
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#1494 KV7

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Posted 19 June 2019 - 0750 AM

 

Interesting outline.  The fact that radar pulses are encoded uniquely is not a surprise - figured that.  Also, that the network is big, durable, and cheap.  But, the elimination of the sidelobe is interesting.  Also, that it overcomes the low signal return using a longer length of time to gather signal.  Never saw that coming.  All in all, it looks like the result of massive data transfer rates inherent to 5G tech.

I hope that isn’t classified.

 

What do you think might be classified ?


Edited by KV7, 19 June 2019 - 0751 AM.

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#1495 KV7

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Posted 19 June 2019 - 0854 AM

Some articles on the use of machine learning to improve resolution in VHF:


'Altitude Measurement of Low-elevation target for VHF Radar Based on Weighted Sparse Bayesian Learning'
 

https://www.research...yesian_Learning

'Altitude measurement based on characteristics reversal by deep neural network for VHF radar'

https://www.research...k_for_VHF_radar


Edited by KV7, 19 June 2019 - 2323 PM.

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#1496 Nobu

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Posted 19 June 2019 - 0957 AM

Posted with tongue planted firmly in cheek, as the debut of the F117 does not feel like it was that long ago. 


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#1497 glenn239

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Posted 19 June 2019 - 1055 AM

Posted with tongue planted firmly in cheek, as the debut of the F117 does not feel like it was that long ago. 

 

How does the F-117 of the 1980's relate to the type of datalink transfer rates and data processing/AI needed for this stuff?


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#1498 Nobu

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Posted 19 June 2019 - 1108 AM

An illustration of how far we have come from the very notion of stealth itself being classified. I can remember the amazement factor at the public unveiling of it.


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#1499 Josh

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Posted 19 June 2019 - 2047 PM

Saying the word 'stealth' isn't classified. I'm going out on a limb and assuming just saying '5G' isn't either.


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#1500 Nobu

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Posted 19 June 2019 - 2304 PM

Chinese, such as the authors of those articles, should be discouraged from doing so too openly, lest someone lose another embassy.


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