DOUBLE FOLDING VITERBI DECODER

摘要

PURPOSE: A double folding Viterbi decoder is provided to save the electric power by reducing a size of an ACS circuit and a size of a PM cell and simplifying a state transition degree. CONSTITUTION: A size of an ACS(Add Compare Select) circuit is reduced by forming the ACS circuit with three adders/subtracters and three increment/decrement portions. An EPRML trellis of a folding Viterbi detector is divided into two trellises of butterfly shape. The first ACS circuit is used for calculating a probable distance of the trellis of a state of 111/000, 100/011 to a state of 111/000, 110/001. The first ACS circuit is formed with two adder/subtracters and two increment/decrement portions. The second ACS circuit is used for calculating the probable distance of the trellis of a state of 111/001, 101/010 to a state of 100/011, 101/010. The second ACS circuit is formed with two adder/subtracters and two increment/decrement portions.