High-speed optical disk drive

If the read speed is increased while high-frequency modulated carrier is fixed at a constant frequency, it becomes difficult to separate the read signal from the carrier by using bandwidth limitation of the analog system because the upper limit of the read signal band nears to the carrier frequency. Moreover, if the separation between them is eased by raising the carrier frequency, a problem that write-waveform controls become difficult arises. However, the carrier amplitude can be suppressed simultaneously preventing leakage to the read signal band by converting the carrier frequency into the stop-band of the adaptive equalizer by making the use of aliasing that occurs at the A/D conversion.