Optimal quantization noise management in wideband fractional-N PLLs

Quantization errors often produce the dominant phase noise component in wide-band fractional-N phase locked loops (PLLs). Recently, a few techniques have been proposed to alleviate the issue, at the cost of extra components. This work illustrates the possibility to significantly reduce the impact of quantization errors without additional building blocks, only relying on an optimal design of the noise shaping features of the ΔΣ modulator driving the PLL divider. In a representative design example the reduction in the peak noise density appreciated via linearized models can be better than 18 dB.