Title:
周波数シンセサイザ
Document Type and Number:
Japanese Patent JP4357674
Kind Code:
B2
Abstract:
The present invention pertains to a type of frequency synthesizer which can correctly compensate for the ripple current. Frequency synthesizer 1 has PLL loop containing oscillator 31 and charge pump circuit 35. Also, the frequency synthesizer has compensating circuit 41 and correcting circuit 43. Said correcting circuit 43 has sense amplifier 44, up/down counter 45, and DA converter 40. The compensating circuit superimposes a compensating current onto the output current of charge pump circuit 35 which generates the control signal of oscillator 31, and it compensates for the ripple current contained in the output current. After the PLL loop is locked, sense amplifier 44 detects the ripple current with the superimposed compensating current, and based on the detection result, up/down counter 45 and DA converter 40 control compensating circuit 43, and the difference between the ripple current and the compensating current is reduced. Consequently, even when the ripple current varies due to variation in the circuit constants, etc., it is possible to cancel out the ripple current accurately.
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Inventors:
Kozo Ichimaru
Application Number:
JP33317399A
Publication Date:
November 04, 2009
Filing Date:
November 24, 1999
Export Citation:
Assignee:
Texas Instruments Japan Ltd.
International Classes:
H03L7/197; H03L7/089; H03L7/093
Domestic Patent References:
| JP11103251A | ||||
| JP8065160A |
Attorney, Agent or Firm:
Shigeo Ishijima
Hideki Abe
Hideki Abe