Patent ID: 6904007
Filing Date: 2005-06-07
Classification: G11B

Abstract:
1. A method of calibrating a loop gain of a loop gain amplifier in a digital servo system, comprising: receiving optical signals from an optical pick-up unit in an optical disk drive; closing the digital servo system with a first loop gain, the digital servo system calculating a control signal based on the optical signals; applying a sinusoidal disturbance at a cross-over frequency to the control signal generated by the digital servo system to form a second control signal; controlling a position of the optical pick-up unit with the second control signal; calculating a discrete Fourier transform of the sinusoidal disturbance at the cross-over frequency to form a disturbance DFT; calculating a discrete Fourier transform of the control signal to form a signal DFT; calculating a measured loop gain from a ratio of the disturbance DFT and the signal DFT; and calculating the loop gain from a ratio between the first loop gain and the measured loop gain.