Viterbi decoding method and decoder capable of eliminating phase indeterminacy

摘要

In a Viterbi decoder and a Viterbi decoding method, a modulating method and a phase of a carrier wave, employed in a transmitter apparatus can be automatically followed up in a receiver apparatus. The Viterbi decoder is comprised of phase shifting means (61) for shifting a phase of a reproduced carrier wave of a reception signal in response to a phase-shift control signal, thereby producing a phase-shifted signal; distance calculating means (62) for receiving the phase- shifted signal to calculate a square Euclidean distance between a signal point of the phase-shifted signal and a signal point defined in a predetermined modulating method; path metric calculating means (62) for calculating a path metric with respect to each of the phases from the calculated square Euclidean distance value; selecting means for selecting a minimum value of the path metric for each of the phases; and phase-shift control signal producing means (63) for producing the phase-shift control signal used to control the phase shifting means in such a manner that the phase of the reproduced carrier wave of the reception signal is set to a phase corresponding to the minimum path metric value. Also, the Viterbi decoding method is comprised of a first step for shifting (61) a phase of a reproduced carrier wave of a reception signal in response to a phase-shift control signal, thereby producing a phase-shifted signal; a second step for receiving the phase-shifted signal to calculate (51) a square Euclidean distance between a signal point of the phase-shifted signal and a signal point defined in a predetermined modulating method; a third step for calculating (62) a path metric with respect to each of the phases from the calculated square Euclidean distance value; a fourth step for selecting (72) a minimum value of the path metric for each of the phases; and a fifth step for producing (63) the phase-shift control signal used to control the phase shift of the reproduced carrier wave at the first step in such a manner that the phase of the reproduced carrier wave of the reception signal is set to a phase corresponding to the minimum path metric value.