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). 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). 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) 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.