Patent ID: 7570555

Claim:
A digital data demodulator comprising: a synchronous pattern processing unit for receiving a modulation data block and for detecting a synchronous pattern in the modulation data block at a predetermined detection position, the modulation data block comprising the synchronous pattern and a predetermined number of modulation codes the synchronous pattern being located at a front of the predetermined number of modulation codes, and the modulation codes being converted from original digital data; a specific pattern detector for detecting a specific pattern in the modulation data block; a certainty decision unit for determining whether data including the specific pattern is the modulation code when a phase difference is present between a first plurality of data identified on a basis of the specific pattern detected by the specific pattern detector and a second plurality of data identified on a basis of the synchronous pattern detected by the synchronous pattern processing unit; a modulation code identifying unit for identifying the first plurality of data as the modulation codes on a basis of the modulation code including the specific pattern, detecting the phase difference, and correcting the detection position of the synchronous pattern in the synchronous pattern processing unit according to the phase difference when the certainty decision unit decides that the data including the specific pattern is the modulation code; and a demodulating unit for reproducing, to the original digital data, the modulation codes identified by the modulation code identifying unit when the certainty decision unit decides that the data including the specific pattern is the modulation code, wherein the certainty decision unit detects a predetermined number of data, the predetermined number of data being identified on a basis of the data including the specific pattern detected by the specific pattern detector, and the certainty decision unit counts a number of undecodable data from the predetermined number of data and decides that the data including the specific pattern detected by the specific pattern detector is the modulation code when the counted number is not larger than a threshold value indicating certainty of the specific pattern.