A Family of ∆Σ Modulators with High Spur Immunity and Low Folded Nonlinearity Noise when used in Fractional-N Frequency Synthesizers

Digital Delta Sigma modulators (DDSM) are typically used in phase locked loops for fractional frequency synthesis. Different types and configurations of DDSMs have been presented in the past which have distinctive characteristics in terms of spectral shaping of the quantization errors, spur immunity and implementation cost. In this paper we present a family of DDSMs that have high spur immunity and low folded noise when used in fractional-N frequency synthesizers.