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Science Technology

Dolphins' Hunting Technique Inspires New Radar Device 79

Posted by samzenpus
from the flipper-power dept.
minty3 writes "The twin inverted pulse radar (TWIPR) made by a team from the University of Southampton in England uses the same technique dolphins do to capture prey. Like dolphins, the device sends out two pulses in quick succession to cancel out background noise. The findings, published in the journal Proceedings of the Royal Society A: Mathematical and Physical Sciences, explained how the device resembles the way dolphins send out two pulses in quick succession to cancel out background noise."
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Dolphins' Hunting Technique Inspires New Radar Device

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  • by cold fjord (826450) on Wednesday October 23, 2013 @10:18PM (#45219885)

    They mysteries and wonder of creation still have many secrets to reveal and lessons to instruct the attentive.

  • by Jmc23 (2353706) on Wednesday October 23, 2013 @10:19PM (#45219891) Journal
    The researcher did not actually investigate what it is that dolphins do, he thought of what they could possibly do.

    I would be more interested in finding out if this is actually the technique dolphins use or do they do something different?

    • by goombah99 (560566) on Wednesday October 23, 2013 @11:40PM (#45220341)

      I used to do something similar with unterminated co-ax cables for baseline subtraction. A box car integrator is short pulsewidth sampler. If one's baseline is large and fluctuating the traditional and expensive way to remove this is double pulse correlated subtraction. Which is nothing more that sampling things twice in succession and subtracting. Unfortunately that's not only expensive in terms of fast rececovery integrator hardware, but if you do it digitally it's got a small difference of large numbers problem as well. The clever way to do this is you don't terminate the coax on the integrator but rather extend the coax past it for a few feet, then leave it unterminated. The pulses thus fly past the integrator which can sample as usual, then 6 nanoseconds later an inverted reflection off the unterminated end pass the sampler in the opposite direction. Anything with fluctuation slower than 6 nanoseconds cancels out before the integrator can make the measurement. It's perfect and costs nothing. You dial in the timing with the coax length which is roughly a foot for every 2 nanoseconds.

      Here they are doing this relying on the rephasing from the impedance mismatch of the reflecting object types being different. People who do FM lidar do something similar. It's an old old technique. probably dates back to the invention of coax.

    • by Ungrounded Lightning (62228) on Wednesday October 23, 2013 @11:51PM (#45220393) Journal

      One of the things described was comparing returns from a positive and a negative pulse, to detect the presence of rectification. Good idea, but...

      There is another way to do that, which I believe is much more sensitive: Send the pulse on one frequency, listen for the return on a harmonic. Only nonlinear devices (mainly semiconductor junctions - constructed or accidental, like corroded metal joints) will produce the harmonic reflection.

      This is how the "bury diodes in the drywall" bug works. The diode(s) sends a strong second harmonic reflection, essentially nothing else does. When the wall moves slightly, due to ambient sound it, varies the length of the transmitter-diode-receiver path, phase modulating the harmonic signal with the audio signal.

      Because only change in phase matters, many diodes in the wall don't interfere with each other, but combine their randomly-phased reflections to make the wall more reflective (just like OFDM reception improving when you have multipath "interference").

      "Illluminate" the building with a stable microwave carrier and listen to the second harmonic (shifted down) with an FM receiver - recovering the sound from the room adjacent to the diode-doped wall. Nothing to it.

      • There is another way to do that, which I believe is much more sensitive: Send the pulse on one frequency, listen for the return on a harmonic.

        That is a really clever idea, but if you are doing this at radar frequencies (for spatial resolution) wouldn't the harmonics be difficult to detect? Would the semiconductor junctions of the size used in current semiconductor devices be sufficiently efficient radiators at the harmonic frequency?

        On the other hand, perhaps you don't need the spatial resolution of radar for the applications mentioned in the article.

        I am not an EE, as is probably obvious.

        • ... if you are doing this at radar frequencies (for spatial resolution) wouldn't the harmonics be difficult to detect?

          Piece of cake. Just pick a fundamental where the second harmonic is in a quiet frequency. Your second harmonic signal will stand out like a sore thumb.

          It's also phase-coherent with your transmitter so you can use a synchronous demodulator to pick it out of a hell of a lot of noise, if there is noise. Phase-locked is as narrowband and accurately tuned as it gets: Your bandwidth is the sho

      • There is another way to do that, which I believe is much more sensitive: Send the pulse on one frequency, listen for the return on a harmonic.

        This is a follow-on to my earlier question, about the difficulty of receiving the harmonics of a radar-frequency interrogation pulse. If the pulse consisted of two distinct frequencies (or was transmitted in addition to a continuous illumination at a different frequency), would a diode or other nonlinear reflector generate a return signal at the beat frequency?

    • by TheLink (130905)
      Yeah there are many other ways of "seeing" through bubbles. Like range-gated cameras/radar/sonar.

      That said I suspect dolphins mostly build a picture or even 3d model of the environment based on the perceived location of the reflections.

      For example, say there is someone talking right in front of you, but you can still listen and aurally locate people who are talking further away behind that person. Even if the person in front is talking loudly, as long as he's not way too loud you can still detect the positi
      • The sensations of hearing, sight, touch, and to some extent smell are all different ways for the brain to model 3D space. Different ways for the universe to observe itself.
      • [...] you could clap your hands (or click your tongue) and hear the location of the echoes in the room. With practice you can identify the rough shape of the room and even location of large objects.

        I suggest the /.ers to try this experiment, it's fun.

        Best results in the dark, during a quiet night so you won't hear much background noise, yet close your eyes.
        Snap your fingers while walking slowly (short whistle also works).

        If you do this walking down a corridor, then you will guess where are the doors, the coats hanging, the turns and crossing very easily.

      • I suspect it has more to do with having two ears and being able to filter out bubble walls. Two ears will give dolphins stereoscopic sonar pinpointing range add in the fact that they are familiar with the response from bubbles and visually can determine their depth and they could easily filter the bubbles returns.
    • by rkww (675767)

      The researcher did not actually investigate what it is that dolphins do, he thought of what they could possibly do. I would be more interested in finding out if this is actually the technique dolphins use or do they do something different?

      Following links to here [discovery.com] we find:

      "As for the dolphin: while acting as an inspiration for the technology, Leighton and his team later discovered this was not how the animals' sonar worked. Dolphins also send out twin pulses, but theirs vary in amplitude, not polarity, h

      • by Jmc23 (2353706)
        Thank you. Lot's of other people posting some quite interesting things, none of which had to do with dolphins :)

        Now I know I'm going to have some weird dreams tonight trying to figure out how exactly dolphins perceive that!

  • by ArbitraryName (3391191) on Wednesday October 23, 2013 @10:19PM (#45219895)
    How many pulses do dolphins and this radar send, and what purpose does that serve?
  • by Anonymous Coward on Wednesday October 23, 2013 @10:26PM (#45219935)

    http://en.wikipedia.org/wiki/Correlated_double_sampling

  • I expected much more description of what the concept meant and how it worked.

    • by Longjmp (632577)
      Well, the summary describes it:
      The radar "sends out two pulses in quick succession to cancel out background noise", like dolphins which "send out two pulses in quick succession to cancel out background noise".

      I also think that sending out two pulses in quick succession may cancel out background noise.

      *eyes rolling at 300 rpm*
      • by mrbester (200927)

        In this case the two pulses cancelled out the signal instead of the noise. Or the summariser is a relative of Foghorn Leghorn.

        • by Longjmp (632577)
          Or the signal cancels out the dolphins. Whatever.
          • by rts008 (812749)

            You forgot the standard prefix to your comment, comrade:

            "In Soviet Russia...."

            So, no fish for you, bad dolphin... ;-)

    • > I expected much more description of what the concept meant and how it worked.

      Totally spit-balling but maybe it works like differential electrical signals. In short two signals inverted from each other, if there is any background noise it is canceled out when you subtract one signal from the other to get the desired waveform.

      https://en.wikipedia.org/wiki/Differential_signaling [wikipedia.org]

      • by Required Snark (1702878) on Wednesday October 23, 2013 @11:33PM (#45220295)
        Follow the link and RTFM

        Radar clutter suppression and target discrimination using twin inverted pulses [royalsocie...ishing.org]

        The proposition that the use of twin inverted pulses could enhance radar is tested. This twin inverted pulse radar (TWIPR) is applied to five targets. A representative target of interest (a dipole with a diode across its feedpoint) is typical of covert circuitry one might wish to detect (e.g. in devices associated with covert communications, espionage or explosives), and then distinguish from other metal (‘garbage’ or ‘clutter’), here represented by an aluminium plate and a rusty bench clamp. In addition, two models of mobile phones are tested to see whether TWIPR can distinguish whether each is off, on or whether it contains a valid SIM card. Given that a small, inexpensive, lightweight device requiring no batteries can produce a signal that is 50dB above clutter in this test, the options are discussed for using such technology for animal tagging or to allow the location and identification of buried personnel who opt to carry them (rescue workers, skiers in avalanche areas, miners, etc.). The results offer the possibility that buried catastrophe victims not carrying such tags might still be located by TWIPR scattering from their mobile phones, even when the phones are turned off or the batteries have no charge remaining.

        • by Longjmp (632577)
          Meanwhile I've read all linked articles, and none of them describes how it actually works, which was GP's question.
          Quoting an absolute meaningless part of TFA doesn't help either.
      • by wagnerrp (1305589)

        There's a bit of confusion over the meaning of background noise. In this example, it's not stray sound or RF, but reflections from things you don't care about. For dolphins, they're talking about air bubbles in the water. For this RADAR system, they're talking about brush and rubble. The idea of differential signalling does not apply here.

        Basically, they're sending two pulses, shifted 180. They both bounce off the target, come back, and cancel each other out at the receiving antenna, yielding no respon

        • by Longjmp (632577)
          Since none of the articles explains technical details, I can only speculate about the dolphins (which is more interesting anyway).
          If their second "click" is used as a reference signal, i.e., the signal itself, not its echo, it could be used not only to invert the first signal and filter out the noise, but also give information about the distance:
          Depending on when the reflected echo comes in - delayed (and overlaid) - to the reference (second) signal it would also account for the distance of the target.
        • It acts like a material discriminator, in that certain interesting materials, such as wires or micro-circuitry, invert only one of the reflections, so instead of cancelling each other out, they amplify.

          The discussion of "twin inverted pulse sonar" clearly states that one signal is inverted from the other. So if only one signal gets inverted during reflection they aren't amplifying, they are canceling.

          Seems more likely that "hard" objects cleanly invert both signals while "noisy" ones like bubbles or brush fuzz up both signals, essentially adding noise that the receiver can then subtract by subtracting the two signals. In which case this is classic differential signaling.

          "As its name suggests, TWIPS uses

        • There's a bit of confusion over the meaning of background noise. In this example, it's not stray sound or RF, but reflections from things you don't care about. For dolphins, they're talking about air bubbles in the water. .

          That's because it is called clutter, the royal society article title Radar clutter suppression and target discrimination using twin inverted pulses I suspect minty3 did not RTFA or even has the slightest understanding of Radar, my theory is given more weight by the poor summary. He probably skimmed the 1st paragraph of one of the puff piece articles he linked to and called it good.

  • by faffod (905810) on Wednesday October 23, 2013 @11:35PM (#45220315)
    Reading the summary I was wondering if this would have any applications to improve detection of stealth aircraft. So I *gulp please don't mod me to oblivion* read the article. It's light on details, but not what I expected from the summary. The guy was able to build a sonar, followed by a radar that is able to distinguish between different materials. It's potential uses are for detecting explosives hidden in rubble and such, and for finding buried victims after some form of disaster (specifically homing in on their phones and other such devices). Oh, and it's cheap, if you know what you're doing you can build it for two bucks.
  • Wonder if that's patentable since there's clearly prior art on nature then...
    • Re: (Score:2, Insightful)

      by Anonymous Coward

      Wonder if that's patentable since there's clearly prior art on nature then...

      Easy, you just sequence the dolphins DNA and patent that.

  • I wonder if the device sends out two pulses in quick succession to cancel out background noise?

  • Like dolphins, the device sends out two pulses in quick succession to cancel out background noise. The findings, published in the journal Proceedings of the Royal Society A: Mathematical and Physical Sciences, explained how the device resembles the way dolphins send out two pulses in quick succession to cancel out background noise."

    Quickly copy and paste the same line twice then add crap in between to create echo chamber effects.

  • Things like this need to be banned from the patent office as unpatentable due to prior art. This rule needs to be dealt out retroactively - should clear up a lot of the bad patents.

    • Otherwise some patent troll will go after the dolphins. This may be the only way to kill the trolls - they can be cited for interfering with wildlife or something. Kind of like getting Al Capone on tax evasion, though if you ask me, Al's business model was more ethical than the trolls'. At least he delivered product.

    • Hmm, if someone's been paying license fees only to have the patent retroactively ruled invalid, can they get a refund from the troll?
  • From TFA:

    The results offer the possibility that buried catastrophe victims not carrying such tags might still be located by TWIPR

    ... Search and Rescue teams need to switch from using dogs to dolphins - duh.

    Think of how many more people could be quickly found in building rubble or IEDs found by battlefield personnel if the teams were using search dolphins. The military could even equip them with lasers to support combat operations with, unlike sharks, no need for night-vision goggles. Think of the real-world applications people.

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