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Dolphins' Hunting Technique Inspires New Radar Device
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."
They mysteries and wonder of creation still have many secrets to reveal and lessons to instruct the attentive.
much of left-wing thought is a kind of playing with fire by people who don't even know that fire is hot - George Orwell
I would be more interested in finding out if this is actually the technique dolphins use or do they do something different?
Don't complain about syntax, grammar, or spelling. There is no.hell like input on android.
How many pulses do dolphins and this radar send, and what purpose does that serve?
http://en.wikipedia.org/wiki/Correlated_double_sampling
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*
There are fewer illiterates than people who can't read.
In this case the two pulses cancelled out the signal instead of the noise. Or the summariser is a relative of Foghorn Leghorn.
"Wait. Something's happening. It's opening up! My God, it's full of apricots!"
> 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
When information is power, privacy is freedom.
Only if the device sends out two pulses in quick succession, which resembles the way dolphins send out two pulses in quick succession to cancel out background noise.
Radar clutter suppression and target discrimination using twin inverted pulses
Why is Snark Required?
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.
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.
Some drink at the fountain of knowledge. Others just gargle.
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.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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.
There are fewer illiterates than people who can't read.
Wonder if that's patentable since there's clearly prior art on nature then...
Easy, you just sequence the dolphins DNA and patent that.
[...] 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.