Using Microwave Technique for Detection of Hazardous Substances
Centimeter- or millimeter-range microwaves can provide images of objects, that are concealed inside passenger’s luggage or on human body under clothes. Apart from that microwave technique can be used to determine dielectric properties of concealed objects with high accuracy thus distinguishing between, say, an explosive material and a wallet containing papers and credit cards.
Unlike “terahertz” method, centimeter-range microwaves have higher penetrating ability to “see through” wet clothes, and operate from distances of several meters at high air humidity. Also, elemental base for this frequency range is more available and much cheaper than for “terahertz”.
Different approaches can be used to receive and process data, to reconstruct and analyze obtained image. For example, multi-antennae “radars” with continuous-wave quasi-monochromatic radiation with step-by-step frequency change can be used. Continuous-wave approach may be preferable, since it uses a well-defined frequency range, which will not interfere with operation of other electric appliances. Choice of the frequency range should be made on the basis of a compromise between desired image resolution, penetration depth, and cost and availability of components.
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