Signal-to-Noise Ratio in a Partial-Response Maximum-Likelihood Detection
Shuichi Ohkubo, Masatsugu Ogawa, Masaki Nakano, Hiromi Honma, Toshiaki Iwanaga · Japanese Journal of Applied Physics · 2004
In this paper we describe a derivation of general expression of signal-to-noise ratio (SNR) in a partial-response maximum-likelihood (PRML) detection system. Because of media noise, as well as difference of transfer function between target PR and the actual channel, the noise at the Viterbi detector is no longer white but colored. The conventional expression of SNR is not appropriate for evaluating signal quality for the colored noise. We have shown how to calculate the variance of the colored noise in the PRML system. The derived SNR can be easily calculated using hardware and is very useful for evaluating signal quality under high-density recording conditions where jitter cannot be accurately measured. We have confirmed that the bit error rate (bER) predicted by the SNR correlates well with the actual bER, regardless of bit density.