Method for determining incline angle of electromagnetic pointer

A method for determining an incline angle of an electromagnetic pointer, the electromagnetic pointer being positioned on or above a digitizer, the digitizer having a plurality of loop antennas, said method comprising steps of:

• A. locating a peak-value loop antenna which has a maximum inductive signal value;
• B. scanning plural loop antennas that are near to the peak-value loop antenna and obtaining seven inductive signal values from seven loop antennas among the peak-value loop antenna and the neighboring loop antennas;
• C. simulating one signal curve with a cubic equation in one variable for every four adjacent points taken from the seven signal values, in which highest-ordered parameters for four signal curves obtained from the simulation respectively are A−2, A−1, A0, and A1 in order;
• D. defining following variables by calculating variations among the signal curves:
• Index1=A0−A−1
• DeltaL=A0−A−2
• DeltaR=A1−A−1
• Index2=DeltaL−DeltaR;
• E. determining an inductive distance between the electromagnetic pointer and the digitizer according to values of DeltaL and DeltaR;
• and
• F. determining an incline angle of the electromagnetic pointer by using values of Index1 and Index2 to look up an incline angle conversion table.