Now, dolphin-inspired radar to detect hidden explosives

Inspired by the way dolphins hunt using bubble nets, scientists have developed a new radar system that can detect hidden surveillance equipment and explosives.
Researchers at the University of Southampton, in collaboration with University College London and Cobham Technical Services, developed the twin inverted pulse radar (TWIPR).
It can distinguish true 'targets', such as certain types of electronic circuits that may be used in explosive or espionage devices, from 'clutter' (other metallic items like pipes, drinks cans, nails for example) that may be mistaken for a genuine target by traditional radar and metal detectors.
The new system has been developed by a team led by Professor Tim Leighton from the Southampton University's Institute of Sound and Vibration Research and is based on his unique sonar concept called twin inverted pulse sonar (TWIPS).

TWIPS exploits the natural abilities of dolphins to process their sonar signals to distinguish between targets and clutter in bubbly water.
Some dolphins have been observed to blow 'bubble nets' around schools of fish, which force the fish to cluster together, and their sonar would not work if they could not distinguish the fish from the bubbles.

The technique uses a signal consisting of two pulses in quick succession, one identical to the other, but phase inverted.
Researchers showed that TWIPS could enhance linear scatter from the target, while simultaneously suppressing nonlinear scattering from oceanic bubbles.
Leighton's team proposed that the TWIPS method could be applied to electromagnetic waves and that the same technique would work with radar.

They teamed up with Professor Hugh Griffiths and Dr Kenneth Tong of University College London and Dr David Daniels of Cobham Technical Services to test the proposal.
Researchers applied TWIPR radar pulses to a 'target' (a dipole antenna with a diode across its feedpoint - typical of circuitry in devices associated with covert communications, espionage or explosives) to distinguish it from 'clutter' (represented by an aluminium plate and a rusty bench clamp).
In the test, the tiny target showed up 100,000 times more powerfully than the clutter signal from an aluminium plate measuring 34 cm by 40 cm.
Given that the diode target measures 6 cm in length, is inexpensive and requires no batteries, it could be a great device to attach to animals for tracking purposes.

It could even be attached to humans entering hazardous areas, particularly where they might be underground or buried.