US Patent 7230458 Delta/sigma frequency discriminator

Delta/sigma frequency discriminator (1) for converting a frequency (Fv) of an input signal into a digital output signal (C) comprising a frequency divider (8) which divides the input signal at a frequency dividing ratio which can be switched in dependence on the digital output signal (C), with at least one sampling register (12) which samples the divided input signal by means of a reference clock signal for generating the digital output signal (C), and with a dither circuit (15) which varies the clock period (T) of the reference clock signal so that interfering modulation tones in the signal spectrum of the digital output signal (C) are suppressed.