| 摘要 |
PURPOSE:To realize a frequency synthesizer with inexpensive configuration and high resolution by controlling the oscillated frequency of a 1st voltage controlled oscillator in a double loop comprising 1st and 2nd phase locked loops and providing a 3rd phase locked loop and a 2nd frequency converter converting the frequency of an output signal. CONSTITUTION:An output signal of the 1st voltage controlled oscillator 24 is controlled by two phase locked loops 35, 40 and a signal with low noise is outputted from the 1st voltage controlled oscillator 24. Moreover, the variable frequency oscillator 26 consists of the 3rd phase locked loop 45 comprising the 2nd voltage controlled oscillator 41, the 2nd variable frequency divider 42 and the 3rd phase/frequency comparator 43 and a 2nd frequency divider 46 frequency-dividing the output signal of the 3rd phase locked loop 45 and supplying the result to a 90 deg. shifter 27. Thus, the noise component included in the signal outputted from the 3rd phase locked loop 45 is reduced by the frequency divider 46. Furthermore, the signal frequency outputted from the 1st voltage controlled oscillator 24 is adjusted by the 1st variable frequency divider 31 and the 2nd variable frequency divider 42. Thus, the frequency synthesizer with high resolution and low cost is obtained. |
