An analog EPR4 Viterbi detector in read channel IC for magnetic hard disks

This EPR4 detector uses a series of read channel ICs that implements all of the essential core function in analog, sampled-data domain. These read channel ICs are similar to the previously reported PR4 Channel in which both the timing recovery and the equalizer are implemented identically. Notable differences/additions include: An (1+D) filter to shape the PR4 response to EPR4 signaling; EPR4 metric calculator; a 16/17 encoder-decoder with (0,6/8) constraints to improve coding efficiency and to minimize error propagation. The entire Viterbi processor is clocked at half the code clock.