| 摘要 |
PURPOSE: To obtain a low-noise frequency synthesizer, having low phase noise and a spurious level by adjusting a gain of a phase detection means for compensating a change in a division number and providing a digital control means that selects a 1st or 2nd division number. CONSTITUTION: A 1st divider 13 receives an input signal f1 and outputs a reference frequency signal fR which is equal to an input signal divided by a 1st dividing number N. A voltage-controlled oscillator 18 generates an output fO of the frequency synthesizer. A divider 15 receives the output fO and outputs a reference frequency signal fC equal to an output signal, divided by a 2nd dividing number M. A phase/frequency detector 14 compares the reference frequencies fR, fC to produce a phase error output signal, and the gain is controlled by a gain control output voltage signal GC of a D/A converter 12. A digital controller 20 adjusts the gain of the detector 14 to compensate a change in the division number and selects a 1st or 2nd division number N, M. Thus, the divider which uses a half of an integer division number and the low-noise frequency synthesizer which uses analog gain compensation are obtained. |
