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

They mysteries and wonder

[cold fjord]

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

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?

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.