DIGITAL SIGNAL RECORDING AND REPRODUCING APPARATUS, ITS MODULATION CIRCUIT AND DEMODULATION CIRCUIT AS WELL AS MODULATION METHOD OF DIGITAL SIGNAL

摘要

PURPOSE: To improve the accuracy of carrier restoration and power efficiency by inserting a pilot signal for resorting a carrier and using HPF for suppressing a band on which a carrier signal is mounted for completely restoring the carrier. CONSTITUTION: A digital signal passing through an encoder is inputted to a mapper 321 and a relation between the signal points of the signal is set so that a coding gain at the time of combination becomes large. Then, the signal is separated into I and Q channel data so as to output them. First and second HPF 322 and 327 remove components around the DC of output signals. The output signals are inputted to first and second balanced modulators 324 and 328 through first, and second RCF 323 and 328 and they are multiplied by signals obtained by shifting 90 deg. the phase of the clock signal of a frequency similar to a carrier frequency from PL 325 by 90 degrees in a phase shifter 326. The multiplied output signals are synthesized in an adder 330. The pilot signal whose frequency is similar to the carrier frequency from a pilot signal generator 331 is added to the output signal of the adder 330 in an adder 332 so as to output them.