Electronic marker locator system and method

A method for locating electronic marker balls comprising:

• (a) receiving a signal representative of a detected marker ball, the signal including in-phase and quadrature-phase (I and Q) components, each being centered about a first frequency;
• (b) filtering the I and Q components to (i) shift the first frequency to a second frequency, thus producing second frequency I and Q components and (ii) match the second frequency I and Q components to exponential decay characteristics associated with the marker balls;
• (c) integrating a phase of the matched second frequency I and Q components to distinguish the components from noise, the integrating (i) being based upon predetermined gain coefficients and (ii) producing integrated I and Q components in accordance with the predetermined gain coefficients;
• (d) determining a magnitude of the integrated I and Q components to produce an I and Q magnitude vector;
• (e) determining a noise variance associated with the magnitude vector;
• and
• (f) adjusting the predetermined gain coefficients in accordance with the determined noise variance.

An apparatus for locating electronic marker balls comprising:

• means for receiving a signal representative of a detected marker ball, the signal including I and Q components, each being centered about a first frequency;
• means for filtering the I and Q components to (i) shift the first frequency to a second frequency, thus producing second frequency I and Q components and (ii) match the second frequency I and Q components to exponential decay characteristics associated with the marker balls;
• means for integrating a phase of the matched second frequency I and Q components to distinguish the components from noise, the integrating (i) being based upon predetermined gain coefficients and (ii) producing integrated I and Q components in accordance with the predetermined gain coefficients;
• means for determining a magnitude of the integrated I and Q components to produce an I and Q magnitude vector;
• means for determining a noise variance associated with the magnitude vector;
• and
• means for adjusting the predetermined gain coefficients in accordance with the determined noise variance.

A computer readable medium carrying one or more sequences of one or more instruction for execution by one or more processors, the instructions when executed by the one or more processors, cause the one or more processors to perform the steps of:

• receiving a signal representative of a detected marker ball, the signal including in-phase and quadrature-phase (I and Q) components, each being centered about a first frequency;
• filtering the I and Q components to (i) shift the first frequency to a second frequency, thus producing second frequency I and Q components and (ii) match the second frequency I and Q components to exponential decay characteristics associated with the marker balls;
• integrating a phase of the matched second frequency I and Q components to distinguish the components from noise, the integrating (i) being based upon predetermined gain coefficients and (ii) producing integrated I and Q components in accordance with the predetermined gain coefficients;
• determining a magnitude of the integrated I and Q components to produce an I and Q magnitude vector;
• determining a noise variance associated with the magnitude vector;
• and
• adjusting the predetermined gain coefficients in accordance with the determined noise variance.