Bit clock signal generator for use in a digital signal demodulator

Abstract

This invention relates to a digital audio tape recorder using a rotary magnetic head. On the tape which has been recorded using R-DAT, signals forming to the industry standards are recorded at a standard tape speed. The tape is caused to run at a speed faster than the standard tape speed and the recording signal is subjected to high speed reproducing while maintaining the rotational frequency of the head at a rotational speed at the time of recording. For realizing this, a bit clock signal generator for use in a digital signal demodulator is provided, which comprises means for generating a detection window pulse having a predetermined pulse width shorter than a period of a bit clock signal from either of time points of rise and fall of the waveform of a signal to be demodulated, or from both the time points thereof, said signal to be demodulated being a digital signal modulated in accordance with a modulation system such as a system constituted with a periodical signal intermittently including a phase information of the bit clock signal to deliver the detection window pulse to a phase locked loop including a phase comparison circuit and a voltage controlled oscillator as a comparison wave, thus allowing the voltage controlled oscillator in the phase locked loop to generate a bit clock signal, characterized by the provision of means for changing the pulse width of the detection window pulse in correspondence with changes in a bit rate of the demodulated signal.