Patent ID: 7379254
Filing Date: 2008-05-27
Classification: G11B

Abstract:
1. A method of reading a servo track, the servo track comprising a plurality of servo frames that include a set of first servo windows recorded at a first frequency and a set of second servo windows recorded at a second frequency, wherein the first and second servo windows are arranged in a checkerboard-like pattern, the method comprising: detecting a mixed frequency servo signal; filtering the first frequency from the mixed frequency servo signal to generate a first frequency servo signal; filtering the second frequency from the mixed frequency servo signal to generate a second frequency servo signal; and calculating a position error signal based on the first frequency servo signal and the second frequency servo signal, wherein, calculating the position error signal comprises calculating a first position error signal based on the first frequency servo signal, calculating a second position error signal based on the second frequency servo signal, and averaging the first position error signal and the second position error signal, wherein the first position error signal is 180 degrees complementary to the second position error signal.