All-digital frequency synthesis with non-linear differential term for handling frequency perturbations

摘要

An all-digital frequency synthesizer architecture is built around a digitally controlled oscillator (DCO) that is tuned in response to a digital tuning word (OTW). In exemplary embodiments: (1) a gain characteristic (K_DCO) of the digitally controlled oscillator can be determined by observing a digital control word before and after a known change (Δf_max) in the oscillating frequency; (2) a portion (TUNE_TF) of the tuning word can be dithered (1202), and the resultant dithered portion (d_k^TF) can then be applied to a control input of switchable devices within the digitally controlled oscillator; and (3) a non-linear differential term (187, 331) can be used to expedite correction of the digitally controlled oscillator when large phase error changes (335) occur.