| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a frequency synthesizer that reduces a loop band of phase noise in a small area and low current configuration. <P>SOLUTION: The frequency synthesizer includes an oscillator 1 and a TDC circuit 7 for detecting a normalized phase difference between a frequency-divided signal CKV of an output of the oscillator 1 and a reference signal Fref, and controls the frequency of the oscillator 1 on the basis of the normalized phase difference detected by the TDC circuit 7. The TDC circuit 7 includes a second oscillator 711 and a counter 712 for counting the periodicity of an output signal OSC2 of the second oscillator 711, and acquires from the output of the counter 712 a counter value equivalent to the period of the frequency-divided signal CKV and a counter value equivalent to a phase difference between the frequency-divided signal CKV and the reference signal Fref and calculates the normalized phase difference from the counter values. <P>COPYRIGHT: (C)2012,JPO&INPIT |
