Patent ID: 6707855
Filing Date: 2004-03-16
Classification: H03L,H03M

Abstract:
A digital delta-sigma modulator for controlling a multi-modulus divider in a fractional-N frequency synthesizer, comprising:a plurality of delta-sigma modulator stages cascaded in a feed-forward circuit topology and defining an Nth order delta-sigma modulator; input means for receiving a N-bit input control word defining a desired frequency for selection, said desired frequency having an integer component part and a fractional component part; sign-bit input means for receiving a direction signal indicating the desired frequency is selected by adding said fractional component part to said integer part or by subtracting said fractional component part from said integer part; and logic means coupled to said delta-sigma modulator stages for detecting and determining the amount and direction of a frequency from the desired frequency to produce a weighted M-bit output multi-modulus divider control word.