FREQUENCY TUNING METHOD FOR VOLTAGE CONTROLLED OSCILLATOR AND PHASE LOCKED LOOP USING THE SAME

摘要

A frequency tuning method for a voltage controlled oscillator includes outputting a first frequency selected from 2ⁿ discrete frequencies included in a frequency tuning range of the voltage controlled oscillator based on a predetermined control voltage and an n-bit control code during coarse tuning; outputting a third frequency corresponding to an average of the first frequency and a second frequency, that is, ½ of a code interval in response to the predetermined control voltage, the n-bit control code, and a control bit; and locking an output frequency of the voltage controlled oscillator to a reference frequency based on an analog control voltage and the third frequency during fine tuning. The second frequency is adjacent to the first frequency amoung the 2ⁿ discrete frequencies and the third frequency is used as an initial frequency in the fine tuning.