Research And Simulation Of All Digital Timing Recovery Technology Of Read/Write Channels Of Hard Disk Drive

With the development of the times,explosive growth of information sets a higher demand on the performance of storage device. Significant progresses have been made on the storage density and access speed of hard disk, which now are the uppermost storage devices in recent years. As one of these progresses, partial-response maximum likelihood (PRML) technique has significantly decreased the bit error on the condition of high density and has further improved the storage density.Timing recovery is one of the most important parts of read/write channel of hard disk drive.Its performance will make a direct influence upon the quality of read/write channel.The existing timing recovery schemes are always based on analog phase locked loop circuit. Its ideology is to make the phase of the local clock to be synchronous with the symbol. there are some disadvantages about this scheme, such as circuit complexity , long lock time, etc.The continuous innovation, such as technology of VLSI and DSP, have made all digital read/write channel possible, and the all-digital timing recovery schemes become a research hotsopt. According to this trend, interpolated timing recovery technology was investigated, and Two kinds of all-digital asynchronous interpolated timing recovery schemes used for the class IV partial response (PRIV) channal were proposed. using raised cosine interpolator is the same point between these two, and the main distinction between these two is the algorithm, i.e., one adopting backforward time error detector (TED) algorithm, but another adopting feedforward TED algorithm.In order to validate the feasible of the schemes, Models based on schemes mentioned above were estabished by MATLAB respectively, including front end signal generation, PR4 equalization, timing recovery, simple decoding ,etc.And the simulation result based on models proved that these two all-digital asynchronous interpolated timing recovery schemes have good performance and can be applied to all-digital read/write channel of hard disk drive.