| 摘要 |
PROBLEM TO BE SOLVED: To provide an FSK modulation circuit capable of narrowing a frequency band of an FSK modulation output signal including frequency variations while keeping an FSK modulation width constant without being attended with increase in the manufacturing cost and deterioration in the yield. SOLUTION: The FSK modulation circuit includes: an oscillation circuit for driving a piezoelectric vibrator X to carry out oscillation operations; an inductor Ls connected in series with the piezoelectric vibrator; a variable capacitor section 1 connected in series with the piezoelectric vibrator and the inductor and the static capacitance of which is controllable; a storage section 3 for storing information with respect to the series resonance frequency of the piezoelectric vibrator; and a control section 2 that selects a set of static capacitance values among a plurality of static capacitance values which the variable capacitor section can take on the basis of the information stored in the storage section, and selects one of the static capacitance value in a set of the selected static capacitance values for the static capacitance value of the variable capacitor section according to a received pulse so as to deviate the oscillating frequency of the oscillation circuit. COPYRIGHT: (C)2006,JPO&NCIPI
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