Patent ID: 7050525
Filing Date: 2006-05-23
Classification: H03L

Abstract:
1. A frequency synthesizer apparatus comprising: a voltage control oscillator operable to generate an output signal having a frequency corresponding to an input control voltage; a variable frequency divider operable to divide the frequency of the output signal from said voltage control oscillator in accordance with an input data corresponding to a number of frequency division, and to output a frequency-divided signal; a phase comparator operable to perform a phase comparison between the output signal from said variable frequency divider and an input reference signal, and to generate and output a signal indicating a result of the phase comparison; a low-pass filter operable to low-pass-filter the output signal from said phase comparator, and to output the low-pass-filtered signal to said voltage control oscillator; a fraction part control circuit operable to receive an input data of a fraction part, to control the input data of the fraction part so as to periodically change the input data of the fraction part according to a predetermined period corresponding to a value of the input data of the fraction part, and to output data of a controlled fraction part; and a first adder operable to add an input data of an integral part to the data of the controlled fraction part outputted from said fraction part control circuit, and to output resultant addition data to said variable frequency divider as the input data corresponding to the number of frequency division, wherein said fraction part control circuit is a plural-(n+m)-th-order delta-sigma modulator circuit, said fraction part control circuit comprising: wherein said first delta-sigma modulator circuit comprises: wherein said second delta-sigma modulator circuit comprises: wherein output data from said second quantizer of said second delta-sigma modulator circuit is inputted to said natural-number-n-th-order differential circuit, wherein said fraction part control circuit further comprises: