Chances are, you know that dolphins use sonar to locate and stun prey underwater. You might also know that they create "bubble nets," in which they trap fish inside a ring of air bubbles that they blow while swimming in a circle. With all those distracting bubbles suspended in the water, though, their sonar needs to work in a special way in order to pick out the fish. Scientists have copied that sonar system, to create a type of radar that could differentiate between ordinary objects and things like explosive devices.

Prof. Tim Leighton, of the University of Southampton in the UK, led the research. His team started out by developing a dolphin-inspired system known as twin inverted pulse sonar, or TWIPS, which we covered in 2010.

In this system, two sonar pulses are sent out in quick succession. Those pulses are identical to one another, except for the fact that they're phase-inverted. When those pulses hit a solid target, it scatters the reflected sound in a linear pattern. Bubbles, on the other hand, produce non-linear scattering. By suppressing the non-linear return signals, TWIPS is therefore able to locate underwater targets amidst bubbles.

The team then decided to see if the same thing would work using electromagnetic waves, as opposed to the sound pulses used in sonar. It did work, the result being what is called twin inverted pulse radar, or TWIPR. In this case, however, the target produces non-linear scattering, while the "clutter" signals are linear.

The researchers successfully used TWIPR to pick out a tiny dipole antenna with a diode across its feedpoint (the sort of electronics often found in bombs or covert communications devices), which was located amidst an aluminum plate and a rusty bench clamp.

It is hoped that once fully developed, the technology could not only locate things such as explosives, but that it could also be used to monitor the whereabouts of people in hazardous environments who are wearing tags that TWIPR can detect.

A paper on the research was recently published in the journal Proceedings of the Royal Society A.