An Ultracompact 9.4–14.8-GHz Transformer-Based Fractional-N All-Digital PLL in 40-nm CMOS

In this paper, we apply various area reduction techniques on an inductor–capacitor (LC)-tank oscillator in order to make its size comparable to that of ring oscillators (ROs), while still retaining its salient features of excellent phase noise and low sensitivity to supply variations. The resulting oscillator employs a proposed ultracompact...