Digital signal magnetic recording/reproducing apparatus using amplitude phase shift keying and frequency-multiplexing

A digital signal magnetic recording/reproducing apparatus comprising:

• a divider, said divider dividing an input digital signal into first to Nth digital signals (N is an integer of 2 or more) each having a specified number of bits;
• first to Nth amplitude phase shift keyers, said keyers respectively performing digital amplitude phase shift keyings of said first to Nth digital signals outputted from said divider so as to thereby generate first to Nth modulated signals having respective carrier frequencies which are different from one another such that frequency bands of said first to Nth modulated signals fail to overlap one another, each of said first to Nth amplitude phase shift keyers comprising a divider for dividing a corresponding one of said first to Nth digital signals into two signals, and a quadrature biphase modulator for quadrature biphase modulating said two signals to obtain a corresponding one of said first to Nth modulated signals;
• an adder, said adder adding said first to Nth modulated signals respectively outputted from said first to Nth digital amplitude phase shift keyers;
• a magnetic recording and reproducing means for recording an output signal from said adder on a magnetic recording medium and for reproducing the recorded signal from said magnetic recording medium;
• first to Nth filters, said filters respectively taking out first to Nth reproduced modulated signals from a reproduced signals from said magnetic recording and reproducing means;
• first to Nth demodulators, said demodulators respectively demodulating the first to Nth reproduced modulated signals respectively outputted from said first to Nth filters;
• first to Nth decoders, said decoders respectively decoding first to Nth demodulated signals respectively outputted from said first to Nth demodulators;
• and
• a mixer, said mixer mixing first to Nth decoded digital signals respectively outputted from said first to Nth decoded digital signals respectively outputted from said first to Nth decoders by inversely processing the operation of said divider so as to thereby generate a reproduced digital signal of one sequence;
• wherein said first to Nth digital signals are in the order form the lowest to highest in allowable error, and said first to Nth amplitude phase shift keyers are in the order from the lowest to highest in error rate after demodulating and decoding a modulated signal obtained thereby.