The Effects of Tape Dropouts on Pulse Compression Recording

Abstract

It is widely recognized that tape dropouts are the major impediment to error-free recording in high density digital recorders (HDDR). Conceptually, the effects of tape dropouts on error performance can be combatted by error correcting codes, signal design or a combination of the two. In this paper the effect of tape dropouts on wide time-bandwidth signals is considered. Wide time-bandwidth signaling techniques, commonly refered to as pulse compression, would appear to be capable of combatting the effects of short tape dropouts. Although the wide time-bandwidth signals are, to a certain degree, immune to short signal dropouts, an excessive performance penalty is paid when dropouts exceed about 10% of the signal duration. The effects of tape dropouts are shown to effectively reduce noise margin by decreasing the signal detection filter output and by introducing intersymbol interference through increased sidelobe levels.