Patent ID: 8653808

Claim:
A method for frequency detection and detecting variation of frequency comprising: providing a pointer on an electromagnetic position detection apparatus, the pointer emitting a signal with a frequency f 1 to the electromagnetic position detection apparatus; generating a base integration signal according to a current integration period x and the signal with the frequency f 1 by the electromagnetic position detection apparatus; generating a current integration signal according to the current integration period x and a predetermined integration period y and a predetermined signal with a Predetermined frequency f 0 by the electromagnetic position detection apparatus; and calculating a variation of frequency Δf between the predetermined frequency f 0 and a current frequency f c according to the base integration signal and the current integration signal by the electromagnetic position detection apparatus, wherein the current frequency f c is calculated via selecting a number of cycles of the signal with the frequency f 1 and a number of cycles of the predetermined signal with the frequency f 0 .