Trellis sequence detector for detecting a quadrature servo signal in disk recording systems

摘要

A trellis sequence detector is disclosed for detecting a quadrature servo signal in optical disk storage devices. The quadrature servo signal is generated in discrete time and comprises two sinusoidal signals phase offset by 90 degrees. The sampling frequency of the quadrature signal is controlled relative to the track crossing velocity so as to produce a fixed number of samples per period of the sinusoid (i.e., per track crossing). In the embodiment disclosed herein, the sampling of the sinusoidal signals is controlled such that there are eight samples per track crossing. The eight samples are associated with a state transition diagram and corresponding trellis diagram which define the operation of a trellis sequence detector. The trellis sequence detector processes the actual samples of the quadrature signal to determine an estimated quadrature sequence closest to the actual samples of the quadrature signal. In this manner, spurious pulses in the actual quadrature signal are filtered out which significantly enhances the performance of the servo system.