Broadband Electromagnetic Sensing for Weapons Detection

The interest in detecting hand-carried weapons has significantly increased due to the recent trend toward relaxation of concealed weapons laws. In 1995, the Justice Dept launched a 2.15 million dollar initiative to develop and field-test several concealed weapons detection technologies. The methods being studied include low-frequency electromagnetic detection, passive milimeter wave imaging, magnetic radiation, low level x-rays, radar and ultrasound, and low frequency magnetic imaging. We propose a new innovative low-frequency electromagnetic induction method that measures the characteristic canonical resonance spectra of a suite of known weapons and matches the measured spectrum from a hidden weapon with those stored in computer memory. We have accumulated evidence that the broadband resonance characteristics can detect and usiquely identify a weapon (eventually and hopefully by its maker and model name). We will utilize an existing in-house broadband, prototype EM sensor (called GEM-3) that is capable of measuring time - or frequency-domain data. Through our frequency-domain processing , we will address the relationship between the poles in the rational-polynomial approximation to the model frequencies. Through our time-domain processing, we will address the analgous problem of estimating the numbe of resonant modes excited. The unique feature that our prototype sensor allows is the simultaneous generation of frequency- and time-domain data. In the course of this proposed program, we will systematically study the relative merits of processing time- and frequency-domain data and the method of fusing the two response characteristics.