Clock recovery on unequalized magnetic recording channels

As new data recovery schemes based on sampling detectors are devised, a need for quick but exhaustive bit error rate characterization becomes important. Hardware prototypes provide the only practical means by which detection schemes can be evaluated at error rates required in a product. Issues such as clock recovery and automatic gain control are often ignored during the evaluation of detection schemes in software, but loom as important issues when it is time to build the prototype channel. In this paper, a technique for performing gradient based clock recovery on unequalized playback channels will be proposed. This phase detector relies on knowledge of the step response of the channel as well as the stored data. Depending upon the phase margin of the phase-locked loop during tracking mode, this phase detector can also be used in a data driven mode