Multiple-values digital signal magnetic recording and reproducing apparatus using a QAM and PSK modulator, pilot signal and a viterbi decoder

摘要

A digital signal magnetic recording and reproducing apparatus includes an encoding portion for convolutionally coding an input digital data, a modulating portion for quadrature-amplitude-modulating and phase-shift-keying-modulating the convolutionally coded digital data, a pilot signal mixer for generating a pilot signal and adding it to the modulated signal, and a recording controller for forming a magnetized signal suitable for a magnetic recording medium from the modulated signal mixed with the pilot signal. The apparatus also includes a reproducing controller for outputting a digital signal, in which distortion and deterioration produced during transmission are corrected, from the magnetized signal reproduced in the magnetic recording medium, a carrier wave restoring portion for generating a clock signal at the carrier signal frequency in response to a pilot signal in the reproduced magnetized signal, a demodulating portion for demodulating the quadrature-amplitude-modulated signal output from the reproducing controller and a decoding portion for outputting original digital data by Viterbi-decoding convolutionally coded data from the demodulating portion. The apparatus increases frequency utilization efficiency by adopting a multiple valued digital modulation method, which is effective in recording in a high density signal. The apparatus is characterized in that the overall signal processing is processed digitally.