Hitachi, Ltd.

Hitachi Video Engineering, Incorporated

Hitachi Video Eng. Inc.

Yoshitomo Kuwamoto

Masanori Ienaka

Junichi Nakagawa

Hidefumi Kimura

Hideaki Watanabe

Jun'ichi Nakagawa

Hiroshi Shirai

Osamu Numata

Shinichi Hagiya

A radio communication apparatus capable of carrying out transmission and reception of signals at a time has a frequency synthesizer and a frequency modulator both in novel structures for removing interference between a local signal and a transmission signal. The frequency synthesizer has a local oscillator controlled by a first phase comparator for phase-comparing a frequency divided output of the local oscillator and a reference frequency signal to provide a local signal. The frequency division of the output of the local oscillator is effectd by a first frequency divider for dividing the frequency of the output of the local oscillator and a variable division ratio frequency divider for dividing the frequency of the output of the first frequency divider. The frequency modulator has a transmission oscillator controlled by a second phase comparator for phase-comparing the output of the first frequency divider and a frequency divided output of the transmission oscillator to provide a transmission signal. The frequency division of the output of the transmission oscillator is effected by a second frequency divider.

Radio communication apparatus free from interference between local

A necessary signal portion of a control signal transmitted from a land station of a mobile telecommunication system during an idle period thereof is received intermittently by a mobile station, with an initial unstable operation period of the mobile station occurring in a period of an unnecessary signal portion of the control signal and a subsequent stable operation period thereof occurring in a period of the necessary signal portion of the control signal.

Control signal receiving system

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

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Yokosuka, Japan

Yoshitomo Kuwamoto