17. The frequency modulator of claim 9 , wherein said DCO is part of an all-digital PLL (ADPLL).
9. A frequency modulator comprising: a digitally-controlled oscillator (DCO), arranged for producing a frequency deviation in response to an integer tuning word and a fractional tuning word; and a DCO interface circuit, arranged for generating said integer tuning word and said fractional tuning word to said DCO, wherein said fractional tuning word is obtained through asynchronous sampling of a fixed-point tuning word; wherein samples of said fractional tuning word are synchronous to a resonant frequency of said DCO.