A waveform-shaping millimeter-wave oscillator with 184.7dBc/Hz FOM in 40nm digital CMOS process

In this paper, a topology for millimeter-wave (mm­ wave) oscillator with a waveform-shaping operation is proposed with improved phase-noise. The 3rd harmonic enhancement for enforcing a pseudo-square voltage waveform and adjustable tuning-banks for wide tuning range are simultaneously achieved, based on a multi-stage broadside-coupled transformer (MSBCT) with recon gurable coupling factors at mm-wave. Meanwhile, to meet the high-Q, high-resolution, and metal density limits, a novel 3D self-shielded capacitor is developed for implementation of tuning-banks operating at mm-wave. To verify the mechanism of the structures above, a waveform-shaping mm-wave digitally­ controlled oscillator (DCO) is fabricated. The proposed oscillator has a state-of-the-art gure-of-merit (FoM) of 184.7dBcIHz at 58.1 GHz under 110°C, despite being realized in a digital CMOS 40nm process without customary ultra-thick metal option. The resolution for this DCO is about 2.5MHz within the whole tuning range. The chip core size is 315um by llOum.Index Terms-3D self-shielded capacitor, digitally-controlled oscillator (DCO), multi-stage broadside-coupled transformer (MSBCT), waveform-shaping, millimeter-wave (mm-wave).