A technique to improve capture range of a PLL in PRML read channel

A new technique to improve the capture range of a Phase Locked Loop (PLL) in the context of partial response signalling is presented. A known preamble is transmitted at the beginning to aid phase and frequency locking. Previous timing recovery techniques have a false locking problem for large initial frequency errors. The new technique eliminates this problem by using information available in the sampled preamble sequence. The improvement obtained is demonstrated using computer simulations.