Patent ID: 6731699
Filing Date: 2004-05-04
Classification: G11B,H03M

Abstract:
Detector (30) for detecting a digital signal (Bio) out of an input information signal (Ai) which represents a runlength limited sequence, the runlength having a minimal value m, the detector (30) comprising,means (60, 62) for generating a preliminary binary signal (Bi) out of said input information signal (Ai), means (86) for identifying a composed sequence of subsequent bits within the preliminary binary signal (Bi) which subsequently comprises at least a first neighboring bit of a unipolar sequence of length greater or equal than m+1, one or more further unipolar sequences of length m and at least a second neighboring bit of a unipolar sequence of length greater or equal than m+1, a unipolar sequence being defined as a sequence of bits having the same binary value, and bordering at both sides at a bit having the opposite binary value, means (84, 86) for generating a set of sequences which can be obtained from said composed sequence by changing polarities of binary values within said composed sequence without violating the runlength constraint, the set comprising the composed sequence obtained from the preliminary binary signal, means (94, 96) for calculating a path metric (D) for two or more sequences of said set, said path metric (D) being the sum of the branch metrics (d) for the path through the trellis corresponding to said sequence of binary values, means (86, 98, 100) for identifying the sequence from said set which has the highest likelihood of correspondence to the input sequence represented by the input information signal (Ai) on the basis of the path metric.