Patent ID: 7893774
Filing Date: 2011-02-22
Classification: H03L

Abstract:
1. A VCO driving circuit that inputs a control signal to a control terminal of a voltage controlled oscillator, the VCO driving circuit comprising: a coarse adjustment DAC that receives digital data having a coarse adjustment frequency to output an analog signal; a fine adjustment DAC that receives digital data having a fine adjustment frequency to output an analog signal; a first LPF that removes noise from an output signal from the coarse adjustment DAC, the first LPF having frequency pass characteristics that allow only a low frequency component to pass therethrough; a voltage dividing means that divides a voltage of an output from the fine adjustment DAC; a resistor that connects an input stage of the first LPF to an input stage of the voltage dividing means; a third LPF that smoothes out an output signal from the first LPF and then provides the resulting signal as an input to the control terminal of the voltage controlled oscillator; and a capacitor that provides a capacitive coupling such that the voltage divided by the voltage dividing means is applied to the output of the first LPF.