Anti radaiation AAM can lock onto AESA's!!!!

urmomma158 · 08-10-2006, 15:46 PM

scary stuff here check this out.

Quote:

U.S. radar designers insist that the latest AESA radar models are all frequency-hopping and therefore they do not emit a signal long enough at a specific point on the bandwidth for such a seeker to lock on to them. But Russian specialists reply that the threat model used by the U.S. to develop these radars relies on older versions of the 9B-1032 seeker. The new version for export, they claim, employs a number of new-generation components that are more sensitive and process signals faster.

http://www.ainonline.com/Publication...improved10.htm

Damn this stuff is scary. Do you think there is a way to take this on or no.

HistoricalDavid · 08-10-2006, 16:24 PM

'They claim'.

AESA radars have not been developed for missiles yet anywhere, and already the Russians claim have counter-AESA small enough for missiles?

Laughable.

urmomma158 · 08-10-2006, 16:45 PM

I thought the Russians we're close to making one or at least have a prototype or something hidden somewhere. Can anyone show me why it won't work on an AESA please.I'm not an expert on anti radaiation or AESA"s for that matter.

highsea · 08-10-2006, 18:15 PM

LPI signals cannot be processed with a snapshot of data. The best RWR's take a second or more of continuous transmission to process normal signals. LPI signals are measured in nanoseconds, and are well below the threshold for todays processors.

AESA sets send out multiple signals on multiple frequencies at multiple power levels simultaneously, and they jump randomly. I find it very hard to believe that Russia can pack the processing power needed to decode LPI modulations into a seeker-sized package.

Methinks Vympel wants to sell missiles...

Archer · 08-11-2006, 03:36 AM

Quote:

AESA sets send out multiple signals on multiple frequencies at multiple power levels simultaneously, and they jump randomly. I find it very hard to believe that Russia can pack the processing power needed to decode LPI modulations into a seeker-sized package.

ACtually, its one freq at a time- the switching can be pretty fast though.

Anon · 08-11-2006, 05:43 AM

Quote:

Originally Posted by Archer

ACtually, its one freq at a time- the switching can be pretty fast though.

I think Highseas has that right. Each individual T/R module emmits on a slightly different frequency...each putting out a tiny amount of power.

That's what makes it LPI to begin with.

highsea · 08-11-2006, 13:27 PM

Quote:

Originally Posted by M21Sniper

...Each individual T/R module emmits on a slightly different frequency...each putting out a tiny amount of power.

That's what makes it LPI to begin with.

Yep.

Archer · 08-11-2006, 18:42 PM

Quote:

Originally Posted by M21Sniper

I think Highseas has that right. Each individual T/R module emmits on a slightly different frequency...each putting out a tiny amount of power.

That's what makes it LPI to begin with.

Thats a common misconception M21. The transmitted signals from individual modules (the group tasked for a particular function, say A2A) all have to be at the same frequency to be received in a coherent manner and then processed. The LPI comes from varying the frequencies and power levels, to mask them in ambient noise. True spread-spectrum frequency hopping AESAs- where each Tx module is at its own frequency etc, and the received signals- each at their own frequency, power level are then "combined" to create an actual picture, are yet to be invented, and the software to run such an op would make the JSF / F-22 look like childs play in comparison. There are hardware restrictions as well.

What can be done today however, is to "split" the radar. Ie you have 1500 modules, you can dedicate a 4th to A2A, another 4th to datalinking/comms, another 4th to A2G, another 4th to EW- this if achieved will represent a pinnacle of current ability. Right now, per indications they arent talking of interleaving modes, but actually implementing comms modes & EW modes on the JSF/F-22 etc- though some modules may be specifically tasked for this- which would allow simultaneous modes to run & hence interleave.
The other way to interleave is of course to follow the PESA method, ie switch the beam (from all 1500) so fast that you scan both air and ground targets- this avoids the issue of dedicating modules for specific tasks and taking a consequent hit in performance.
But of course, if one splits the available Tx/Rx modules up- you take a hit in total available power for the given function, which has an effect on range. (Basically average power & peak power) Another thing is that most ranges given for the high end AESA radars, are normally under non LPI conditions. To achieve optimum range, you have to "squawk", and break LPI to go to normal emission- if you do that though, you run the risk of being detected by normal 3rd generation RWRs- which are increasingly accurate and function as high accuracy direction finders. So what you would prefer is that your non LPI sensor is actually far off from your axis while it feeds you information or your entire formation is passive only whilst it soaks up high bandwidth data from other sensors (AWACS) etc. Now if you combine even the reduced LPI range radar with an airframe with stealth, what you do get is still a detection advantage- but to truly play to your strengths, you might want even more Situational awareness.

All in all, its a nice game of countermeasure vs counter-countermeasure.

Anon · 08-11-2006, 22:38 PM

Thats a common misconception M21. The transmitted signals from individual modules (the group tasked for a particular function, say A2A) all have to be at the same frequency to be received in a coherent manner and then processed.

Again, simply not true.

This is accomplished via massive computing/processing power. The individual returns are 'rebuilt' into a coherent composite image by the jets onboard puters and then displayed on the pilots monitor.

Archer · 08-12-2006, 02:04 AM

Quote:

Originally Posted by M21Sniper

Thats a common misconception M21. The transmitted signals from individual modules (the group tasked for a particular function, say A2A) all have to be at the same frequency to be received in a coherent manner and then processed.

Again, simply not true.

This is accomplished via massive computing/processing power. The individual returns are 'rebuilt' into a coherent composite image by the jets onboard puters and then displayed on the pilots monitor.

M21, its not just processing power. Its the software and algorithms that go into combining these signals together *plus* the hardware that allows you to tune each Tx/ Rx module to a different frequency. Even the APG-79 cannot do this, its basically a 4 channel radar. See, what you are describing is the "ideal"- where returns of different amplitudes, phases, are recieved with their corresponding lags and "combined". Right now, quoting from a discussion elsewhere:

Quote:

"the individual tx/rx modules does not produce individual lobes. The waves originating from them combine to form a single wavefront, and the directional power density is determined by the phase relationship between the individual signal. If you can vary the phase of the modules linearly, you can have the beam pointing in any angle, without null spots. The problem with PESA is that the phase change is in steps."

"It is already explained how the beam is formed by making a number of emitters radiate waves with specific phase relationship. That is transmission. Let us now see reception.

The beam concept is bidirectional. Just like a dish antenna can both transmit and receive, the phased array can also trasmit and receive. All you need is to add the individual received signals with proper phase relationship.

Let us see how PESA works. You have a single high power signal source feeding a number of emitter modules. The emitter module just contain a variable phase shifter and an antenna element (simplified view!). There is no amplification of the outgoing signal. It just changes the phase of the signal. the received signal also pass through the same phase shifter and gats added up at the back.

You can see that you can not split or group the individual emitters in this technique.

In the first gen AESA, you just add active circuitry (amplifiers) into the individual modules. They are still fed with a master signal, because they should be synchronous to each other PRECISELY. This master signal is phase shifted and fed to a power amplifier. the received signal is fed through the phase shifter and combined at the back. The russian AESA projects have this scheme according to available info.

This scheme also can not do multiple roles for the modules, so it do not offer any functional advantage over PESA. However, it improves reliability and power efficiency.

Next improvement is using multi-channel TX/RX modules. Each module can be fed with multiple master signals. One channel can be selected at a time for operation. So, with a four channel system (eg. APG-79), you can form four different beams at the same time. Note that one module can do only one function at a time, so you got to divide up the modules. The received signals also travel back the same way.

Now, THAT PESA can not do. But this scheme makes the TX/RX modules to cost more and ulky.

The second gen AESA (eg Vixen) uses Direct Digital Synthesis (DDS). Here the outgoing signal is NOT from a master. It is generated using DSP techniques. You still nees a master clock, so all the modules are synchronized in frequency and phase. Each module will have DSP and processors and the master RC will talk to them setting up various waveforms and phases.

This scheme can generate any combination of waves, limited only by software. But this has a major problem. that is received signal.

In the previous techniques, the received signals just passed through the same phase shifter and automatically combined with proper phase relationships. The DDS system need to do it using DSP, the same way it generated the transmit signal. So, the received signal is DSP procesed at the module itelf.

In previous models, you do DSP processing at the combined signal, which has more amplitude. Here we have to process a lower amplitude signal, so the signal to noise ratio is much lower. So, the effective sensitivity of the receiver is much lower here. That in fact offset a lot of advantages.

But there are remarkable adantages. You are no longer limited to a single frequency. You can transmit and receive a spread spectrum signal. You can do frequency hopping. Also, you can do a lot better in weapon guiding, where receiver sensitivity is not THAT important.

And the blessing and curse of this system is the dependance on software. You can smarten or dumb down the performance without anyone knowing it. the manufacturer can provide a friendly user country with a software development kit with libraries, so the user country, like India can create kick-ass modes themselves. Or, the manufacturer can do it the Microsoft Way, by exporting a dumbed down library and SDK. "

From here:

Quote:

OK, let me debunk a major misconception in the discussions on AESA. The notion that each of the modules scan a small area is totally incorrect. If you turn on a single module, it will create a low power wide angle beam almost reaching the entire FOV of the array antenna. The beam is created by interference of the multiple emitters at the correct phase relationship, and the larger the number of modules participating in the beam, the sharper the definition. Needless to say, all emitters participating in a single beam MUST have the EXACTLY same frequency. Otherwise you can not form the beam properly. This is achieved by either a digitally synthesized master signal or using a low power phase shifter approach.

Now this requirement also debunks the notion that being able to use multiple frequencies, AESA is more immune to jamming. The only advantage in this regard would be that it is possible to create multiple beams each with a different frequency.

Quote:

It is not a simple task to vary the frequency emitted by a number of modules while keeping the phase relationships appropriate. It is next to impossible to form a beam out of spread spectrum signals using phased arrays because each component needs a different phase relationship. The only viable method is to dedicate one module for one frequency. It is also possible to use multiple channels in one module, but that is essentially multiple modules in one package.

Also, the signals of all the modules participating in forming a beam MUST be synchronized to each other.

Bottom line, spread spectrum as you know from communication systems doesn't exist in Radars. The best you can do is a bunch of individual frequencies. Now, those returns can not be combined in time domain. You can only combine them on raster. That will not improve detection, but will only aid in resolution.

The poster is of course a old codger in the field.

True spread spectrum AESA's are still in the future- one estimate by a highly experienced RF engineer I spoke to recently, put them at a decade from now in terms of operationalizing the software, but hes basically involved with Euro programs- but the same guy who posted the above also noted that while the hardware may be getting there- the software may be a different issue.

Anyways, the APG-79 is clearly not a DDS based radar, are there any official sources referring to true spread spectrum transmission for the APG-77 etc? I know Global security and similar reports say so- but you know how they can be at times, hit & miss. Perhaps if you know someone who worked on the APG-77 they can clarify the same?

Anon · 08-12-2006, 14:22 PM

It is not a simple task to vary the frequency emitted by a number of modules while keeping the phase relationships appropriate. It is next to impossible to form a beam out of spread spectrum signals using phased arrays because each component needs a different phase relationship. The only viable method is to dedicate one module for one frequency. It is also possible to use multiple channels in one module, but that is essentially multiple modules in one package.

That's from your article, and it states that multiple frequencys is entirely possible....which is convenient, since the F-22s T/Rs all operate on slightly different frequencies, each of which puts out only a few watts of power.

PS: Highseas is 'in the business' and is something of a radar buff. You should probably listen to him. I do.

Archer · 08-12-2006, 21:04 PM

M21, you misread the part,

Quote:

"It is next to impossible to form a beam out of spread spectrum signals using phased arrays because each component needs a different phase relationship."

Ie multiple frequencies from different Tx/ Rx bricks/tiles & recombining is very hard, ie spread spectrum..

followed by:

Quote:

"The only viable method is to dedicate one module for one frequency. It is also possible to use multiple channels in one module, but that is essentially multiple modules in one package."

followed by this part, which you missed:

Quote:

Also, the signals of all the modules participating in forming a beam MUST be synchronized to each other.

ie frequency and phase have to be taken care of..

And,

Quote:

Bottom line, spread spectrum as you know from communication systems doesn't exist in Radars. The best you can do is a bunch of individual frequencies. Now, those returns can not be combined in time domain. You can only combine them on raster. That will not improve detection, but will only aid in resolution.

which ties in with:

Quote:

The beam is created by interference of the multiple emitters at the correct phase relationship, and the larger the number of modules participating in the beam, the sharper the definition. Needless to say, all emitters participating in a single beam MUST have the EXACTLY same frequency. Otherwise you can not form the beam properly. This is achieved by either a digitally synthesized master signal or using a low power phase shifter approach.

Ok...now he does say that it is "theoretically" possible, for 2nd gen (DDS) AESA's..design architecture wise..(note that am referring to entire radar, not brick/tiles in which the US is at iirc 6th generation..)

1st Gen AESA cant do this (design wise):

Quote:

Next improvement is using multi-channel TX/RX modules. Each module can be fed with multiple master signals. One channel can be selected at a time for operation. So, with a four channel system (eg. APG-79), you can form four different beams at the same time. Note that one module can do only one function at a time, so you got to divide up the modules. The received signals also travel back the same way.

2nd gen could..

Quote:

The second gen AESA (eg Vixen) uses Direct Digital Synthesis (DDS). Here the outgoing signal is NOT from a master. It is generated using DSP techniques. You still nees a master clock, so all the modules are synchronized in frequency and phase. Each module will have DSP and processors and the master RC will talk to them setting up various waveforms and phases.

This scheme can generate any combination of waves, limited only by software. But this has a major problem. that is received signal.

In the previous techniques, the received signals just passed through the same phase shifter and automatically combined with proper phase relationships. The DDS system need to do it using DSP, the same way it generated the transmit signal. So, the received signal is DSP procesed at the module itelf.

In previous models, you do DSP processing at the combined signal, which has more amplitude. Here we have to process a lower amplitude signal, so the signal to noise ratio is much lower. So, the effective sensitivity of the receiver is much lower here. That in fact offset a lot of advantages.

But there are remarkable adantages. You are no longer limited to a single frequency. You can transmit and receive a spread spectrum signal. You can do frequency hopping. Also, you can do a lot better in weapon guiding, where receiver sensitivity is not THAT important.

....but as of now, its unclear whether any system actually operates it...we know the APG-79 for instance doesnt, whereas the Selex ones coming out of Europe can technically be modded into doing so...but the million $ question is whether Messr's APG's-77, 81 are likewise or are like Mr 79..and whether the software to pull this off has been actually demonstrated..

I thought Highsea was in structural CAD/ CAE / aerostructure design?

ArmchairGeneral · 08-13-2006, 00:04 AM

Quote:

Originally Posted by Archer

I thought Highsea was in structural CAD/ CAE / aerostructure design?

If I understand correctly, Highsea is a radar/electronics engineer. You may be thinking of jgetti, who is in some area of aircraft design with Boeing; he works a lot on the Hornet and Eagle I believe.

Interesting stuff about AESA. Sounds like you're saying it's kind of a holographic effect, where each element contributes to the whole picture, rather than each element taking a separate smaller picture and then combining them into a big picture.

Archer · 08-13-2006, 02:44 AM

Quote:

Originally Posted by ArmchairGeneral

If I understand correctly, Highsea is a radar/electronics engineer. You may be thinking of jgetti, who is in some area of aircraft design with Boeing; he works a lot on the Hornet and Eagle I believe.

Well iirc he had noted he designed an electromechanical component for an Indian program..so I guessed design...

Quote:

Interesting stuff about AESA. Sounds like you're saying 1. it's kind of a holographic effect, where each element contributes to the whole picture, 2. rather than each element taking a separate smaller picture and then combining them into a big picture.

Well put; I took the liberty of splitting your quote.1
1. Are radars like APG-79
2. Are radars which can do spread spectrum operation

The million $ question was whether the APG-77 indeed operates in the latter..

Anon · 08-13-2006, 03:02 AM

Quote:

Originally Posted by Archer

Ie multiple frequencies from different Tx/ Rx bricks/tiles & recombining is very hard, ie spread spectrum..

Landing a man on the moon(several times) was also very hard. And we also did it.

Very hard is not a synonym for impossible.

Quote:

Originally Posted by Archer

ie frequency and phase have to be taken care of..

which ties in with:

Ok...now he does say that it is "theoretically" possible

Still no show stoppers that i see. Just challenges.

Quote:

Originally Posted by Archer

....but as of now, its unclear whether any system actually operates it...we know the APG-79 for instance doesnt, whereas the Selex ones coming out of Europe can technically be modded into doing so...but the million $ question is whether Messr's APG's-77, 81 are likewise or are like Mr 79..and whether the software to pull this off has been actually demonstrated..

I have always read that each T/R on the APG-77 is on it's own discrete frequency.

I suspect that any questions about LPI and such should be in here:

Classification and Analysis of Low Probability of Intercept Radar Signals Using Image Processing

That's a declassed masters thesis on the subject of LPI, and i'd presume it should cover the various methods used to achieve LPI in detail.

08-10-2006, 18:15 PM	#4 (permalink)
highsea *Defense Professional* Join Date: 12-10-04 Location: Seattle, WA Posts: 3,530	LPI signals cannot be processed with a snapshot of data. The best RWR's take a second or more of continuous transmission to process normal signals. LPI signals are measured in nanoseconds, and are well below the threshold for todays processors. AESA sets send out multiple signals on multiple frequencies at multiple power levels simultaneously, and they jump randomly. I find it very hard to believe that Russia can pack the processing power needed to decode LPI modulations into a seeker-sized package. Methinks Vympel wants to sell missiles... __________________ My baby called me up. She said- Why don't you ever take me out? Pick me up in your brand new car....You shake the short change from the old fruit jar...

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08-10-2006, 16:24 PM	#2 (permalink)
HistoricalDavid Distant Deeps or Skies *Senior Contributor* Join Date: 07-19-05 Location: North London, UK Posts: 2,100 Country:	'They claim'. AESA radars have not been developed for missiles yet anywhere, and already the Russians claim have counter-AESA small enough for missiles? Laughable.

08-10-2006, 16:45 PM	#3 (permalink)
urmomma158 the real plastic *Senior Contributor* Join Date: 03-05-06 Location: NJ Turnpike Posts: 938 Country:	I thought the Russians we're close to making one or at least have a prototype or something hidden somewhere. Can anyone show me why it won't work on an AESA please.I'm not an expert on anti radaiation or AESA"s for that matter.

08-11-2006, 22:38 PM	#9 (permalink)
Anon New Member Join Date: 08-03-03 Posts: 0	Thats a common misconception M21. The transmitted signals from individual modules (the group tasked for a particular function, say A2A) all have to be at the same frequency to be received in a coherent manner and then processed. Again, simply not true. This is accomplished via massive computing/processing power. The individual returns are 'rebuilt' into a coherent composite image by the jets onboard puters and then displayed on the pilots monitor.

08-12-2006, 14:22 PM	#11 (permalink)
Anon New Member Join Date: 08-03-03 Posts: 0	It is not a simple task to vary the frequency emitted by a number of modules while keeping the phase relationships appropriate. It is next to impossible to form a beam out of spread spectrum signals using phased arrays because each component needs a different phase relationship. The only viable method is to dedicate one module for one frequency. It is also possible to use multiple channels in one module, but that is essentially multiple modules in one package. That's from your article, and it states that multiple frequencys is entirely possible....which is convenient, since the F-22s T/Rs all operate on slightly different frequencies, each of which puts out only a few watts of power. PS: Highseas is 'in the business' and is something of a radar buff. You should probably listen to him. I do.

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