Patent ID: 6469862
Filing Date: 2002-10-22
Classification: G11B

Abstract:
A system for processing servo data in an analog read channel signal of a magnetic data storage device, said analog read channel signal including a relatively broad band noise spectrum and a relatively narrow band servo signal centered at a frequency Fs having a bandwidth BWs, comprising:A. an oscillator for generating an oscillator signal at a frequency Fo, where Fo is higher than Fs; B. a multiplier having a first input coupled to said analog read channel signal and a second input coupled to said oscillator signal, and an output providing a multiplier signal representative of the product of said analog read channel signal and said oscillator signal; C. a bandpass filter coupled to said multiplier output and having a center frequency at a frequency Foâˆ’Fs or Fo+Fs and having a bandwidth at least equal to the bandwidth BWs, said filter being responsive to said multiplier signal to generate a filter signal; D. an envelope detector responsive to said filter signal to generate an envelope signal representative of the envelope of said bandpass filter output signal; E. an A/D converter having an input in electrical connection with an output of said envelope detector; and F. a digital filter having an input in electrical connection with an output of said A/D converter.