| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a fractional N frequency synthesizer with low power consumption at low cost. <P>SOLUTION: The fractional N frequency synthesizer 10 includes: a phase detector 14 to which a reference frequency and a comparison frequency are entered; a loop filter 18 to which a control signal from the phase detector is entered; an oscillator 12 to which the control signal filtered through the loop filter is entered for generating an output frequency; and an integer frequency divider 16 for dividing the output frequency, which is entered from the oscillator, using a dividing control number (N+F) and generating the divided output frequency as a comparison frequency to the phase detector. The dividing control frequency consists of an integer (N) and a fraction part (F) having at least two distinct ordered fractions. First and second sigma/delta transformers 20 and 22 generate mainly different fractions. The second sigma/delta transformer 22, which processes the smaller fraction, is operated at a clock frequency smaller than that of the first sigma/delta transformer, which processes the larger fraction. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
