| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a frequency synthesizer which utilizes transmitting and receiving fractional frequency-dividing phase-locked loops which reduce an area occupied by a chip, sharing a sigma delta modulator with each other, and also to provide a frequency synthesizing method. <P>SOLUTION: A frequency difference between a transmitting channel frequency and a receiving channel frequency is kept constant in radio mobile communications using a CDMA technology etc. When the value of a counter outputting a reference frequency is adjusted using the above feature so as to keep the decimal division ratios of the transmitting and receiving fractional frequency-dividing phase-locked loops equal to each other, the numbers of the sigma delta modulators and the counters deciding the reference frequencies can be each reduced to one. Therefore, the frequency synthesizer can be remarkably reduced in chip area and current consumption. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
