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Encryption The Military

US Army Developing Encrypted Radar Waveform (thestack.com) 122

An anonymous reader writes: The U.S. army is working on an innovative technology for masking radar emissions in contested territory and environments with heavily congested radio bands. Effective radar system performance is critical in military operations, yet remains a challenge in locations under attack or in areas of high traffic density. Army researchers have now developed a noise-encrypted radar waveform called Advanced Pulse Compression Noise (APCN), which can be tuned in real-time to allow users to adjust radar performance depending on their surroundings. Research scientist, Mark Govoni explained: 'Having the ability to transmit a radar waveform that's continually changing, one that never repeats itself, and looks like noise, is extremely difficult to intercept....and remains anonymous to radar detectors.'
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US Army Developing Encrypted Radar Waveform

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  • How about anti-radiation missiles?
    • by Anonymous Coward

      I agree. Response Rossiya? The question to ask here is if this adaptation has actual value and if so how can we mitigate this. Radar detection and ECM would have to adapt. The next question would be if it has value how to integrate this feature into S-400/S-500. The final thought on this would be if such an adaptation can not be countered, changes in doctrine will have to be considered such as the more immediate than deferred use of nuclear weapons. Do not cheer this, your lives may become a lot unsafer as

  • So they discovered FHSS [wikipedia.org]. Good for them!

    (Also, they may be able to mask the radar pulses, but "encrypt"? Really?)

    • by Anonymous Coward

      More likely high-rate FFT/IFFT with rotating data, null, and equalization sub-carriers.

    • Re:FHSS (Score:4, Insightful)

      by Daniel Matthews ( 4112743 ) on Thursday March 17, 2016 @01:22AM (#51713155)
      How can they mask the signal if a detector has a larger bandwidth? Part of your spectrum is going to have more energy, even if it is digitally smeared. However if they are also doing something tricky with multiple transmit locations and a random phase array effect a snooper can't even be sure what time period a section of the spectrum belongs in. So not only is your signal dancing around on different frequencies it is also dancing around in space and time so only the receivers with the correct key to track the random sequences can make use of the reflected signal off the targets. So yeah you could really encrypt a radar signal, but they didn't describe what I just did did they? :-)
      • by Anonymous Coward

        Normally in noise radars they emit a gaussian noise signal. This has quite good autocorrelation properties and thus can be used as a pulse compression function. Big disadvantage is the very high peak-to-average power, which I guess is what this project is working on. You can certainly detect is using a radiometer, by measuring an increase in background noise. In areas with a lot of RF usage you will probably blend in quite well, the other side will want to be very careful not to fire the anti-radiation miss

    • Re:FHSS (Score:5, Informative)

      by default luser ( 529332 ) on Thursday March 17, 2016 @01:25AM (#51713167) Journal

      It's not just frequency hopping.

      Radars have a pattern called Staggered PRF Frame, which is a repeating pattern. and this, along with frequency, pulse width and PRI is used to identify a radar.

      We already have frequency agile radars. We can identify them because the other characteristics are still constant.

      If you make the frame look like random noise then it just looks like clutter. VERY hard to spot.

      This is important because you don't just waste HARMs firing at random clutter, and you certainly don't want to accidentally fire on an unexpected friendly.

      • by Viol8 ( 599362 )

        "If you make the frame look like random noise then it just looks like clutter. VERY hard to spot."

        It only has to be slightly above the noise floor to be triangulated. The actual modulation is more or less irrelevant so long as the signal last long enough to pinpoint it.

        • Oh no doubt, you can get a fix on anything.

          But without clear details in the signal, you can't determine if it's friend or foe. And in the land of "friendly fire is not so friendly," that means you need a visual confirmation.

          If you have enough unique detail to identify the platform, then you feel a lot more confident hurling a HARM at it.

      • by Rei ( 128717 )

        Still not new. I was working for Rockwell-Collins back in 2000 and our department went to a lecture from a guy talking about Chinese work on radar. One of the concepts that they were apparently working on was broadcasting broad-spectrum noise and looking for statistical correlations in the return.

    • Re:FHSS (Score:4, Interesting)

      by Balthisar ( 649688 ) on Thursday March 17, 2016 @01:31AM (#51713177) Homepage

      It's been a long time since I was involved with Army radar and encrypted communications (in my case, merely humble air traffic control equipment), but the article intrigued me enough to do a very quick lookup. This article [techlinkcenter.org] isn't very technical, but I can see how it's not simple spread-spectrum radio.

      Remember that the information conveyed by radar microwaves is limited; we're primarily interested in reflections (this is "primary radar"; "secondary" radar actually does transmit information; IFF is a type of secondary radar). For a simple radar we know the radar echoes are ours because they come back to our own dish, and match the frequency that we transmitted. They're also incredibly easy to jam.

      Frequency hopping on its own makes things harder to jam because the frequencies change in a cryptographic pattern. They can still be jammed if your broadcast a lot of noise over the entire spectrum, but then you limit your own communications. If you can detect the point source, though, you can broadcast a point source over the entire spectrum and still jam them.

      What I think I understand about this is that it’s not merely frequency hopping, but the signal modulation is encrypted in a way to evade detection. With a receiver I can detect a typical radar’s 3.4 Ghz signal at -200db (numbers are made up), even if spread across the spectrum, because I know what a 3.4 GHz square wave looks like against the background noise, even if it only appears intermittently on the narrow frequency I’m scanning.

      I could try to modulate the signal a different way; maybe a sawtooth, maybe a sine, but a repeating, predictable signal is observable, even with frequency hopping. However if I broadcast noise (and my receiver knows the noise’ pattern), then any listening equipment shouldn’t be able to pick out my microwave pattern from the background.

      • I see how a noise signal will jam a phased array radar. But what about a conventional moving directional antenna? It should easily detect the direction of the noise source and not be influenced by the jamming while pointing in other directions.
    • by Megol ( 3135005 )

      This is a modification of noise radar intended to make the signals even harder to detect as far as I can tell. While I wouldn't call the signal encrypted it is still true one have to have the "key" to make sense of the radar return. That and a extreme amount of processing power!

  • by mysidia ( 191772 ) on Thursday March 17, 2016 @01:08AM (#51713113)

    Catching speeders.... since vehicle radar detectors won't work for attempting to detect the the encrypted radar signal.

    • by AmiMoJo ( 196126 )

      Jamming is more effective for protecting motorists. Thanks to the development of collision warning and autonomous vehicles it's not perfectly justifiable to mount IR lasers and radar on your car. Police speed guns only interfere with important safety equipment, increasing the probability of an accident.

      In any case, most mobile speed traps use lasers, not radar. The fixed ones are no problem because it's easy to keep a database of where they are - my Nissan came with one built in, and a handy voice prompt wa

    • Catching speeders.... since vehicle radar detectors won't work for attempting to detect the the encrypted radar signal.

      Probably irrelevant due to deployment of average speed cameras anyway...

  • The FBI have already asked for a back door.

  • Curtiss-Wright makes a circuit board that would be perfect for this work. This board [curtisswrightds.com] is an FPGA next to a DAC that can spit out an RF signal whose modulation is about 6 GHz wide, calculated by the FPGA. Using this technology, ANY type of waveform or modulation can be sent to the radar transmitter.

    I just ordered (for my radio astronomy job) its cousin, which is all A/D converter, as our radio telescope doesn't have a transmitter, just a receiver.
  • Presumably this will come with a backdoor for the FBI, right? Just to keep things, fair, right?
  • why would you announce such a thing?
    • by ledow ( 319597 )

      Because it's obvious, anyone in the know probably already has kit that does this, it's in no way a secret, or new, or otherwise unavailable, and all possible opponents are deploying this already.

      But if you make it sound new and exciting, people in the US won't question why they spend more on the military than ANY THING ELSE, EVER, despite not even being at war, and they'll think you're doing things that nobody else has ever done, that sound cool, and so they won't mind frittering money away.

  • by Anonymous Coward

    https://en.wikipedia.org/wiki/Low_probability_of_intercept_radar

    Similar systems are already deployed. The original implementations were a variation on frequency hopping techniques, but they've been becoming more sophisticated as computing power increases.

    It makes them harder to detect, harder to determine the source if detected, and more resistant to jamming. They can still be rendered useless by powerful broadband jamming, but that is rarely used as it blinds everyone, not just the enemy. Though it sho

  • Radar detectors would have to adopt Counter LPI/LPD techniques, which apparently do exist:

    There's a book on Amazon called "Detecting and Classifying Low Probability of Intercept Radar".

  • This sounds like it could be beneficial in many areas of signal transmission. I feel it should be opened to the public.

    The last thing we need is more military capability. In fact, what we really need is more technically capable adversaries to keep us in check and raise the real cost of us going to war to untenable levels.

    So the real answer is ALL of our defense research should be opened to all of mankind. Every last page of it. I would LOVE to see this technology used in commercial drones, in the hands of t

  • Hedy LaMarr (yes) developed spread spectrum frequency hopping for submarine torpedo guidance systems that couldn't be intercepted by the enemy who would then have been able to throw the torpedoes off course. She patented it in 1942. The US Navy started deploying her system in the 1960s during the Cuban missile crisis.

    The same technology gives us WiFi, CTCSS/DCSS, FTTC, n-plexing NFM and WFM radio, CDMA, Bluetooth...

  • Can anyone with access to the papers share what's new about "advanced pulse compression noise" radar versus classic noise radar?

    Noise radar itself, i.e. transmitting white noise and then correlating returns with the original noise signal to find the targets, is not a new technology. I don't doubt there's something new here, but the articles are too light on details to be able to tell what.

    Also, bit of a stretch to call it "encryption"... Methinks that was the managers or the journalists.

    • I was doing that in 1973. But everything in radar repeats at about a 12 year cycle, and that's about the fourth time coded signals have been hailed as revolutionary. The problem is that, if you plug the parameters needed into the radar range equation, the radar receiver needs a lot more sensitivity than the target's radar warning receiver because it's the inverse of the fourth power of the power transmitted vs. the second power at the target. Chopping it into noise-like stuff helps somewhat but you still ne

  • Perhaps the UV background hiss in the Universe could be the carrier for interstellar communications? Using an encryption-key generator, it might be possible to randomly unlock such hidden hidden communications, or use the method to transmit and receive communications using the background noise as the carrier.

He keeps differentiating, flying off on a tangent.

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