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."

Comments

Summary incorrect based on article

[Jmc23]

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?

Any good EE already knows this

[Anonymous Coward]

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

Re:But does it...

[aXis100]

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.

Re:Near Zero Information in the article

[Required Snark]

Follow the link and RTFM

Radar clutter suppression and target discrimination using twin inverted pulses

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.

Re:Just so I'm clear...

[Edis Krad]

The number of pulses and the purpose were written in the summary twice in quick succession, to remove background noise.

a 50 year old technique

[goombah99]

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.

There are also other ways to do some of this.

[Ungrounded Lightning]

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.