FREQUENCY SYNTHESIZER

PURPOSE:To reduce a noise component from a charge pump and to prevent a time to be settled to a desired frequency when a large phase difference takes place from being increased in the frequency synthesizer used for a portable telephone set or the like. CONSTITUTION:When a phase difference detected b...

Ausführliche Beschreibung

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Bibliographische Detailangaben
Hauptverfasser:	TANIGUCHI TOMOYUKI, FUKUBE KENJI, YOSHIDA HIROSHI
Format:	Patent
Sprache:	eng
Schlagworte:	AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATIONOF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES BASIC ELECTRONIC CIRCUITRY ELECTRIC COMMUNICATION TECHNIQUE ELECTRICITY TRANSMISSION
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Beschreibung
Zusammenfassung:	PURPOSE:To reduce a noise component from a charge pump and to prevent a time to be settled to a desired frequency when a large phase difference takes place from being increased in the frequency synthesizer used for a portable telephone set or the like. CONSTITUTION:When a phase difference detected by a phase comparator 14 is large, a control circuit 16 controls the synthesizer so that the conversion gain of a charge pump 15 is increased and the conversion gain of a loop filter 17 is decreased thereby increasing a variable range in a control voltage and decreasing a time to be settled to a desired frequency. Furthermore, when the phase difference is small, the control circuit 16 controls the synthesizer so that the conversion gain of the charge pump 15 is increased and the conversion gain of the loop filter 17 is decreased thereby reducing the noise component from the charge pump 15.