Quantization Noise Cancellation for FDC-Based Fractional-N PLLs

This paper presents a quantization noise cancellation technique for frequency-to-digital converter-based fractional-N phase-locked loops (FDC-PLLs). The technique cancels quantization noise prior to the loop filter so the PLL bandwidth can be increased without a significant phase noise penalty. The paper also presents an FDC-PLL architecture enhancement that achieves the effect of a charge pump offset current to improve linearity without the extra current source required by previous implementations.