Hitachi, Ltd.

Hitachi Video Engineering, Incorporated

Hitachi Video Eng. Inc.

Hidefumi Kimura

Masanori Ienaka

Yoshitomo Kuwamoto

Hideaki Watanabe

Jun'ichi Nakagawa

Junichi Nakagawa

This invention relates to a phase coincidence detector for examining whether or not two input digital signals are coincident by utilizing a delay signal and an advance signal of a digital phase comparator which examines the phase difference between the two input digital signals and outputs the delay signal representing the delay of one of the input signals to the other and the advance signal representing the advance of one of the input signals to the other. Particularly, the output signals of the phase comparator, that is, the delay signal and the advance signal, are periodic pulse signals, and residual pulses having a small pulse width occur periodically even at the time of coincidence. The phase coincidence detector of this invention changes the delay and advance signals by a pulse width discrimination circuit for discriminating whether or not the phase difference between the two input signals is below a certain constant value, and samples the changed signals to output the in-phase and out-of-phase state as signals having different levels.

Phase coincidence detector

In an intermittently operative phase-locked loop, in order to prevent the oscillator frequency from significantly changing at the time of turning on of an electric power source, a point in time at which a phase difference between clock signals respectively fed to a reference frequency divider and to a frequency divider for dividing the output frequency of a voltage-controlled oscillator becomes substantially zero is detected, and the two frequency dividers are initialized when the above-mentioned point in time is detected after turning on of the electric power source.

Power saving intermittently operated phase locked loop

Growing community of inventors

Katsuta, Japan

Hidefumi Kimura