Patent ID: 7974162

Claim:
A digital data modulator-demodulator, comprising: a digital data modulator for modulating digital data and outputting the digital data to a transmission line; and a digital data demodulator for demodulating the digital data modulated by the digital data modulator and performing reproduction to original digital data, wherein the digital data modulator comprises: an error-correcting coder for adding an error-correcting code to digital data for each predetermined capacity to generate an error-correcting code data block; a modulating unit for adding a synchronous pattern to a front of the error-correcting code data block and converting the error-correcting code data block into a modulation code of a second data length for each first data length to generate a modulation data block; and a transmission digital data generating unit for replacing a data string of a specific data length on a specific position of the modulation data block, with a data string of the specific data length including a special code, generating a first transmission digital data block, and outputting the data block to a transmission line, and wherein the digital data demodulator comprises: a synchronous pattern processing unit for detecting the synchronous pattern from a data string of the first transmission digital data block on a predetermined detection position when the data string of the first transmission digital data block is inputted through the transmission line; a special code analyzer for detecting the special code from the data string of the first transmission digital data block and analyzing the detected special code to specify a position of the special code; a modulation code identifying unit including a demodulation cycle counter and a cycle difference detector, the demodulation cycle counter for generating a demodulation data strobe signal on a basis of the data string including the special code detected by the special code analyzer, and the cycle difference detector for detecting a phase difference between data strings of the second data length, the data strings being identified on the basis of the data string including the special code detected by the special code analyzer and the synchronous pattern detected by the synchronous pattern processing unit, to generate a cycle difference detection signal; and a demodulating unit for correcting, according to the position of the special code identified by the special code analyzer and the demodulation data strobe signal, an arrangement of the modulation code when the special code is detected by the special code analyzer, and performing reproduction to original digital data, wherein the synchronous pattern processing unit corrects the detection position of the synchronous pattern according to the cycle difference detection signal.