Patent ID: 8106770

Claim:
A method for detecting a target in a soil including the steps of: generating a transmit signal, the transmit signal including at least three different frequency components, a relatively high frequency component, a relatively medium frequency component and a relatively low frequency component; generating a transmitted magnetic field, based on the transmit signal, for transmission into the soil; receiving a received magnetic field; producing a receive signal induced by the received magnetic field, the receive signal including relatively high frequency components, relatively medium frequency components, and relatively low frequency components; and processing the receive signal, the processing including selecting coefficients for, in effect, linearly combining the relatively high frequency components, the relatively low frequency components and the relatively medium frequency components of the receive signal to produce an indicator output signal, the indicator output signal including a signal indicative of the presence of the target in the soil, and wherein the coefficients are selected such that the indicator output signal is approximately independent of log-linear frequency-dependent resistive signal components and log-uniform resistive signal components from the soil.