Partial response maximum likelihood (PRML) detection trellis method adaptable to signal dropouts

摘要

An adaptive trellis adaptable to read a signal having signal amplitude dropouts includes a standard partial response maximum likelihood (PRML) trellis and an estimating PRML trellis. The standard trellis is associated with a standard state diagram having standard branches between states. A first set of the standard branches produce a non-zero amplitude read signal sample and a second set of the standard branches produce a zero amplitude read signal sample. Each state of the standard state diagram has two standard branches feeding into that state. The estimating trellis is associated with an estimating state diagram having estimating branches between states. The estimating branches produce estimated read signal samples that adapt to the amplitude of the signal. Each state of the estimating state diagram has two estimating branches feeding into that state. Each standard and estimating branch has an associated error metric. Each state of the standard state diagram has two estimating branches feeding into that state and each state of the estimating state diagram has two standard branches feeding into that state. The states are connected by paths formed by branches between the states. A path error metric is the sum of all branch error metrics for all of the branches that form the path. The path arriving at one state having the lowest path error metric survives to be identified as the expected path to the next state for reading the signal.