| 摘要 |
PURPOSE:To eliminate the internal beat by changing the phase comparison frequency of a subloop and the frequency division ratio of an output frequency divider so as to change the oscillated frequency of a voltage controlled oscillator without changing the output frequency. CONSTITUTION:When the oscillating frequency of a 1st VCO 11 and a 2nd VCO 23 satisfies the relation of IF=(f of the 1st VCO)Xn-(f of 2nd VCO)Xm, a spurious radiation is generated and internal beat is produced. In this case, it is noticed that the output of a 2nd PD 25 is unchanged, the frequency division ratio of a 4th PD 26 is selected from 2450 to 2500 as shown in figure, the REF of subloop is selected from 5kHz to 4.9kHz. However, since the N of a 3rd PD 22 remains unchanged, the oscillating frequency of the 2nd VCO 23 is decreased naturally, but since the frequency division ratio of a 2nd PD 21 is selected from 500 to 490, the output is unchanged. |
