Application of broadband EMI responses to infer buried object´s aspect ratio

A new broadband electromagnetic (EMI) sensor, operating as lows as 10s of Hz and as high as 100s of kHz, has shown significant improvement for classification of buried metallic objects. EMI responses ("secondary" or scattered magnetic field) are characterized by two components, one inphase and another in phase quadrature with the primary field. Numerical and experimental investigations show that the frequency location of the quadrature peak in EMI scattered fields from metallic objects depends strongly on the major axis length ratio and on the object\´s orientation relative to the transmitted field. To illustrate potentially useful processing of EMI sensor data, this paper presents results of high fidelity numerical simulations to verify a theory for simple estimation of an object\´s aspect ratio based on the frequency location of the quadrature peak (permeable case). Results are shown for a permeable cylinder and spheroid.