PERD: partial error response detection

Extended Partial Response Maximum Likelihood (EPRML) detection outperforms PRML detection on very high-density magnetic recording channels but is much more complex than PRML and is difficult to implement for high data rates. PERD is an alternative to the EPRML detector which gives even better performance. It consists of a conventional PRML detector and a pattern discrimination circuit operating on the error waveform between the waveform estimated from the PRML outputs and the actual playback waveform. A bit-by-bit simulation confirms the expected performance gains over PRML detection.