| 摘要 |
A FSK modulation circuit comprises a voltage control oscillator (20) for producing fO, a local oscillator (50) for producing fL, a mixer (40) for mixing the outputs of the voltage control oscillator and the local oscillator, a freq. selection switch (80) for selecting an oscillation freq. and a modulation ratio, a programmable freq. divider (70) for dividing the output freq. of the mixer by the freq. selection switch, a crystal oscillator (100) for producing fr, a phase comparator (90) for comparing the phase of fv and fr, a lock detector (10), and a RF output control switch section (30). The circuit is capable of modifying a carrier freq. without replacing the crystal oscillator.
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