| 摘要 |
A cellular phone has consecutively a receiving slot, an idling slot which is either a waiting slot or a peripheral information receiving slot, and a transmitting slot in a single frame. The PLL synthesizer includes a loop filter block between a charge pump and a voltage controlled oscillator to control the locking time of the PLL synthesizer for switching between the oscillation frequencies. The loop filter block selects a first filter having a largest time constant upon switching from a receiving frequency to a transmitting frequency via an idling slot, an intermediate time constant upon switching from the transmitting frequency to the receiving frequency, and a smallest time constant upon switching from the receiving frequency to the transmitting frequency via the peripheral information receiving frequency.
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