Methods for reducing RF interference for improved NQR detection of landmines

Nuclear Quadrupole Resonance (NQR) is being researched as a confirmatory sensor for use in mine detection as part of the research carried out by the Defence Science and Technology Laboratory (Dstl) for the UK MOD Applied Research Programme. NQR is a radio frequency (RF) spectroscopy technique used at close range to detect explosives, typically TNT and RDX, found in anti-tank and anti-personnel landmines. Detection is carried out by averaging NQR data until the signal to noise ratio increases enough for the signal to be distinguished from RF noise and interference. Environmental RF noise dominates the received signal because NQR signals are, in comparison, extremely low in magnitude. Therefore, RF interference, which varies depending on the time of day, environment, and frequency of the radiation, directly affects detection times. Methods of reducing RF interference such as antenna design, signal processing and phase cycling are reviewed and discussed. Results are presented from research undertaken to enhance the signal to noise ratio, taken in various environments.