Phase noise in fractional-N frequency synthesizers employing successive requantizers and MASH-SQ hybrids
Abstract
Noise-shaping quantizers are used in fractional-N PLLs to provide a fractional-mean modulation signal to the loop divider. A drawback to this method is the introduction of phase noise due to the changing divide ratio. Noise shaping techniques are typically employed, but have been shown to produce spurs in the presence of loop nonlinearities. An alternative to the traditional MASH DΔΣM has been introduced in the form of the Successive Requantizer (SQ), which can offer better spurious performance at the expense of area. The MASH-SQ Hybrid combines both approaches to achieve the performance of the SQ with a much reduced implementation cost. In this paper, we summarise the properties of the SQ and a method for estimating the phase noise introduced, before deriving the minimum number of requantization stages required to mask an input modulation signal, and thus present an expression for the optimum MASH-SQ Hybrid size.
Publication Title
PRIME 2017 - 13th Conference on PhD Research in Microelectronics and Electronics, Proceedings
Recommended Citation
Donnelly, Y., & Kennedy, M. (2017). Phase noise in fractional-N frequency synthesizers employing successive requantizers and MASH-SQ hybrids. PRIME 2017 - 13th Conference on PhD Research in Microelectronics and Electronics, Proceedings, 217-220. https://doi.org/10.1109/PRIME.2017.7974146
