| 摘要 |
<P>PROBLEM TO BE SOLVED: To facilitate the inspection of an oscillation frequency range in a phase-locked loop having a function of changing over oscillation frequency characteristics of a plurality of voltage control oscillators. <P>SOLUTION: A PLL frequency synthesizer having a function of changing over oscillation frequency characteristics of a VCO block 15 used for a communication processing part includes: a phase comparator 13 for detecting a phase difference between a desired frequency and the oscillation frequency of the VCO block 15 so as to output a voltage Vcont corresponding to the phase difference; a band selecting circuit 12 for generating a band selection signal BS, based on the desired frequency and the oscillation frequency of the VCO block 15, so as to select the oscillation frequency of the VCO block 15; and a VCO block 15 which is constituted to have a superimposition part between the oscillation frequency characteristics of the VCO block 15 with respect to Vcont and generates a plurality of oscillation frequencies by the use of the band selection signal BS, based on Vcont. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
