Generation of amplitude levels for a partial response maximum likelihood (PRML) bit detector

Partial response maximum likelihood (PRML) bit detection apparatus, comprising:

• input means for receiving an input information signal;
• conversion means for deriving a digital signal from the input information signal, the digital signal including an array of bits of a first or a second binary value occurring at bit instants with a specified bit frequency;
• detection means for repeatedly detecting a state from subsequent sequences of n subsequent bits in the digital signal, the subsequent sequences being obtained by shifting a time window of n subsequent bits each time over one bit in time;
• sample value determining means for deriving sample values from the input information signal, one sample value for each of the sequences of n bits, the one sample value for a sequence of n bits corresponding to the signal value of the input information signal at a predetermined time instant lying within a time window corresponding to the sequence of n bits;
• processing means for processing the sample values belonging to sequences of n bits of the same state, and for carrying out this processing step for all states, so as to obtain a processed signal value for each state;
• output means for supplying the processed signal values for each state as amplitude values;
• means to use the amplitude values for the possible states, obtained from a first portion of the input information signal, for detecting bits from a second portion of the input information signal;
• error detection means for detecting errors in the bits obtained from bit detection on the second portion of the input information signal by the means to use the amplitude values for the possible states;
• and
• means to reject the amplitude values for the possible states, obtained from the first portion of the input information signal in response to the error detection means identifying for the bits obtained from the second portion of the input information signal that it includes an error.