Static viterbi detector for channels utilizing a code having time varying constraints

A detector for use in detecting data in a storage channel, the data being encoded according to a code having a time varying constraint, the detector comprising:

• a Viterbi detector represented by a trellis structure having a plurality of states connected by branches, each state having an associated state metric and each branch having an associated branch metric, the Viterbi detector further comprising, for each state:
• at least one branch metric component determining a predetermined number of branch metrics for the branches leading to the state, the predetermined number being time invariant;
• and
• a state metric component determining a state metric associated with the state based on the branch metrics and based on previous state metrics corresponding to previous states from which the branches connected to the state originated.

A communication channel, comprising:

• an encoder configured to encode data into code words having time varying constraints;
• a rotatable data storage disc which receives and stores encoded data;
• and
• a read channel which reads encoded data from the disc, the read channel including a Viterbi detector having a time invariant structure configured to receive a read signal indicative of the encoded data read from the disc and detect the encoded data in the read signal.

A method of detecting data encoded in a read signal according to a code having time varying constraints, the read signal being received from a read channel, the method comprising steps of:

• providing a Viterbi detector having a time-invariant structure which enforces the time varying constraints on the code;
• receiving the read signal at the Viterbi detector;
• and
• detecting data in the read signal with the Viterbi detector.