Broadband modulation pll, and modulation factor adjustment method thereof

摘要

A problem of the present invention is to provide a wide band modulation PLL having good modulation accuracy at low cost. With respect to a PLL having a VCO ( 21 ), a frequency divider ( 22 ), a phase comparator ( 23 ), a charge pump ( 24 ) and a loop filter ( 25 ), the VCO ( 21 ) and a frequency dividing ratio of the frequency divider ( 22 ) are controlled to perform modulation. The VCO ( 21 ) has two control terminals for PLL and modulation, and a control signal generation part ( 28 ) generates a control voltage V_tm of the VCO ( 21 ) based on phase modulation data and an input voltage V_tl to the control terminal for PLL. At the time of adjusting a modulation factor, the control voltage V_tm to the control terminal for modulation of the VCO ( 21 ) is controlled and also the input voltage V_tl is measured and a modulation sensitivity of a frequency of the VCO ( 21 ) to V_tm is calculated and a modulation factor of the phase modulation data is adjusted based on the modulation sensitivity obtained.