Tuning Word Retiming of a Digitally-Controlled Oscillator Using RF Built-In Self Test

This paper represents an innovative solution to reduce phase noise present on the GMSK modulated spectrum in an all-digital RF transmitter employing a discrete-time oscillator. The root cause of this issue is the improper timing of oscillator tuning word update with respect to the digitally-controlled oscillator (DCO) capacitor state. Using the built-in self test (BIST) circuit in the all-digital PLL (ADPLL), the DCO tuning word update timing is calibrated such that the impact on the phase noise is compensated and desired modulated spectrum margin from the specification is achieved