Quasi-synchronous sampling and adaptive partial-response maximum-likelihood read-channel system

We propose a read-channel system with quasi-synchronous sampling and an adaptive partial-response maximum-likelihood (PRML) method to achieve accurate timing recovery and correct data extraction under high-density recording with a high transfer rate. The proposed system can extract data correctly in the state of either oversampling or undersampling using first-in-first-out flip-flops (FIFOs) and an asynchronously sampled data processable maximum-likelihood detector (ASML). In other words, it allows a sampling clock to be incompletely synchronized with a channel bit. Furthermore, the ASML adaptively learns the references required for calculating branch metrics even though the input data are not synchronized with the channel bit. This system achieves stable data extraction under quasi-synchronous sampling, improves the bit-error-rate performance, and can be applied to next-generation, high-density, and high-transfer-rate storage systems.