| 摘要 |
A local oscillator circuit has a control loop that locks the oscillation of a voltage-controlled oscillator at a programmable frequency. The control loop includes a voltage generator that generates a control voltage for the voltage-controlled oscillator, and a current generator that generates a current to raise and lower the control voltage. The magnitude of the current is switched according to the programmed frequency. The magnitude of the current can thereby be adjusted so that the local oscillator circuit achieves lock within a predetermined time, without the need for analog comparison of the control voltage.
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