| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency direct modulator capable of suppressing noise for an adjacent communication channel caused by temperature variation of modulation frequency. SOLUTION: In the frequency direct modulator performing frequency modulation by applying a voltage dependent on transmission data (DATA) to the control terminals V1 and V2 of a voltage controlled oscillator 24 not through a phase locked loop 6, temperature dependency of the terminal voltage at the time of PLL and of the unlocked modulation voltage is set to conform with the temperature dependency of a varicap diode. Since temperature dependency of modulation index can be made extremely small and power leak to an adjacent channel can be suppressed, noise for the adjacent communication channel can be suppressed. COPYRIGHT: (C)2005,JPO&NCIPI
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