25.1 A highly-digital frequency synthesizer using ring-oscillator frequency-to-digital conversion and noise cancellation. - Colin Weltin-Wu; Guobi Zhao; Ian Galton (ISSCC, 2015)

A 3.5 GHz Digital Fractional-N PLL Frequency Synthesizer Based on Ring Oscillator Frequency-to-Digital Conversion. - Colin Weltin-Wu; Guobi Zhao; Ian Galton (IEEE J. Solid State Circuits, 2015)