MASH-Based Divider Controllers for Mitigation of Wandering Spurs in a Fractional-N Frequency Synthesizer

Wandering Spur Suppression in a 4.9-GHz Fractional-N Frequency Synthesizer

“…Adding high-amplitude dither d 2 [n] at the input to the third-stage EFM in a MASH 1-1-1 introduces noise that is uncorrelated with e 2 [n] and can, thereby, mitigate wandering spurs [8]. As shown in [8], the dither signal d 2 [n] can be effective for mitigating wandering spurs. When dither d 2 [n] is applied, the output of the third-stage EFM is…”

“…The required range of the uniform random number source for the uniform dither solution is [0, M). In the theoretical analysis of the quantization noise of a MASH 1-1-1 DDSM, the quantization noise from the third-stage EFM1 e 3 [n] is often considered to be uniformly distributed in [0, M) [8].…”

“…In [8], several dither transfer functions that are effective in mitigating wandering spurs have been presented. As an equivalent to the uniformly distributed explicit dither, a dither transfer function…”

“…can be used. As mentioned in [8], a first-order shaped equivalent dither can be achieved by choosing a suitable dither transfer function. Therefore, we also consider the dither transfer function…”

“…Modified MASH DDSM architectures for the mitigation of wandering spurs were proposed in [8], and preliminary measurement results were presented in [9]. In this work, we review the underlying mechanism that gives rise to wandering spurs in Section II and present details of the implementation of two wandering spur suppression techniques in a 4.9-GHz 180-nm SiGe BiCMOS charge-pump PLL (CP-PLL) synthesizer platform-high amplitude dither and a modified MASH DDSM-in Sections III and IV.…”