Patent ID: 6617856
Filing Date: 2003-09-09
Classification: G01V

Abstract:
An apparatus for locating electronic marker balls, comprising:a matched filter configured to receive in-phase and quadrature-phase (I and Q) detection signals, the I and Q detection signals representative of resonant frequencies associated with one or more of the marker balls, the I and Q detection signals including a first frequency, wherein the matched filter (i) shifts the first frequency to a second frequency and (ii) matches the second frequency I and Q components to exponential decay characteristics associated with the marker balls; a coherent integrator configured to (i) receive the matched second frequency I and Q components, (ii) integrate a phase of the matched second frequency I and Q components based upon predetermined gain coefficients, and (iii) produce an integrated signal thereby, the matching distinguishing the components from noise; a magnitude detector coupled to the coherent integrator, wherein the magnitude detector determines a magnitude of the integrated signal and produces a magnitude vector representative of the determine magnitude; and a filter coupled to the magnitude detector, wherein the filter determines a noise variance associated with the magnitude vector and adjusts the predetermined gain coefficients.