| 摘要 |
PURPOSE:To attain miniaturization and low power consumption by forming a phase comparator circuit with a counter circuit and a latch circuit as a digital circuit and adopting a digital circuit for a loop filter connecting to its post-stage. CONSTITUTION:A phase comparator circuit consists of a counter circuit 15 and a 1st latch circuit 16 as digital configuration and a digital circuit is adopted for a loop filter connecting to a post-stage. Moreover, a D/A converter circuit 18 is connected to a post stage of the digital loop filter 17 to use an output of the digital loop filter for a control voltage of a voltage controlled oscillator (VSO). Thus, since the phase comparator circuit and the loop filter 17 being major circuits of a conventional frequency synthesizer are configured as digital circuits, an A/D converter circuit having been used for a conventional frequency synthesizer is not required. Thus, the compensation error in a VCO characteristic fluctuation due to a difference between the A/D converter circuit and the D/A converter circuit is eliminated. |
