An Inductorless Fractional-N PLL Using Harmonic-Mixer-Based Dual Feedback and High-OSR Delta-Sigma-Modulator with Phase-Domain Filtering

Abstract

An inductorless Harmonic-Mixer (HM) based fractional-N PLL is proposed. It simultaneously achieves Delta-Sigma-Modulator (DSM) noise suppression and a wide loop bandwidth by employing a high-OSR DSM and nested-PLL-based phase-domain lowpass filtering inside of the dual-feedback architecture. A 2.8-3.5 GHz prototype implemented in 65-nm CMOS achieves a -227.6dB FoM with an 8 MHz bandwidth, with no calibration circuitry and with a compact layout containing no inductors.