Radar is used by the military and first responders for identifying concealed explosive devices and people buried under rubble. Spurious reflections cause clutter in any radar system, short range or long range. It would help if there was a way to determine if the radar reflection was from an electronic device like a cellphone. Researchers at the University of Southampton, University College London and Cobham Technical Services may have a solution – radar clutter suppression and target discrimination using twin inverted pulses.
The system works by distinguishing linear scatter (from a metal plate, for example) from non-linear scatter (from a dipole and diode, for example). Two pulses are transmitted in quick succession, with the second identical but phase inverted, to distinguish linear and non-linear scatters. This is similar to twin inverted pulse sonar (TWIPS) that has been shown to be effective in distinguishing targets from bubble clutter.
Twin inverted pulse radar (TWIPR) distinguishes objects that scatter radar linearly from non-linear scatters that generate odd and even harmonic when scattering radar pulses. Rusty metal connections generate primarily odd harmonics, which allows them to be distinguished from semiconductor junctions in a cell phone, for example.
A complete description of TWIPR and graphs showing how it works is available in the Proceedings of the Royal Society paper Radar clutter suppression and target discrimination using twin inverted pulses
by T. G. Leighton, G. H. Chua, P. R. White, K. F. Tong, H. D. Griffiths and D. J. Daniels.