Chapter 11 - Peak detection channel

Abstract

Peak detection channel is a simple and reliable method of data detection. It was the first detection channel utilized in magnetic disk drives. This chapter describes the main principles of peak detection channel operation and considers the error rates of this channel. A block diagram of a typical peak detection channel is shown, which is based on the assumption that each transition results in a relatively sharp peak of voltage. The goal of the peak detection channel is to detect each individual voltage peak. The error rate at the threshold detector is determined by the probability of drop-outs when the pulse amplitude falls below the specified threshold, or the probability of strong noise outbursts when total media and electronic noise exceeds the specified signal level. The error rate at the zero-crossing detector is determined by random shifts of the zero-crossing position from the correct peak location. Random noises cause fluctuations of the zero-crossing position in the differentiated readback signal. An error occurs when the zero-crossing position falls beyond the detection window, that is, when zero-crossing is detected earlier or later than the current bit cell. The calculation bit error rate is examined.