DEVICE FOR RECONSTRUCTING A RUNLENGTH CONSTRAINED SEQUENCE

摘要

A device is described for reconstructing a runlength constrained sequence of n-ary digits from an analog input signal (Si) representing said sequence, the device comprises an input (1) for receiving said signal (Si) coupled to a sampling unit (2) for taking time-discrete samples of the input signal (Si). The device further comprises a branch metric calculation unit (3) for calculating a set of branch metric values (BMs,n) for subsequent samples (Ssn) of the sampled input signal (Ss). Each of the set of branch metric values is an indication for the likelihood that an amplitude value of a sample (Ssn) corresponds to a particular state (s), a state being defined as a sequence of n-ary digits. The device further comprises a delay unit (4i) which forms part of a delay chain (4) of delay units. A first delay unit (4a) of the delay chain is coupled to the branch metric calculation unit (3). The device further comprises a path metric calculation chain (5) of path metric calculation units, the path metric calculation chain (5) comprising one or more path metric calculation units (5b) having first inputs (5b1) coupled to a delay unit (4g) and second inputs (5b2) coupled to a preceding path metric calculation unit (5a). The path metric calculation unit (5a) calculate the path metric values (PMs,n-k) out of the branch metric values (BMs,n), a path metric value being an indication for the likelihood that a sequence of samples corresponds to a sequence of states.