The system of mail explosive detection based on NQR

A system of mail explosive detection based on Nuclear Quadrupole Resonance (NQR) is introduced. Using direct data synthesis (DDS) to customize stimulation pulse sequence, the phase, amplitude and frequency of stimulation pulse can be controlled accurately by the computer. An automatic tuning technique is used to enable the detector to be only sensitive to the interesting frequency point. The temperature-frequency regulation function is also integrated in the system to modify stimulating frequency according to the temperature of sample. The system adopts a variable weighting data processing algorithm to suppress interference and so as to increase its signal to noise ratio. (authors)