A 19-to-45 GHz High-Efficiency Frequency Doubler Using Multi-Port Darlington Cell With Fundamental and Second-Harmonic Pole-Stagger in 55-nm CMOS

A millimeter-wave (mm-Wave) ultra-wideband high-efficiency frequency doubler without any buffer and switching is proposed in this article. The proposed frequency doubler employs a new multi-port Darlington cell (MPDC) pair to incorporate a secondary feedback path for the 2nd harmonic generated at the drain terminal to the gate terminal. The positive feedback is created to override the negative feedback from gate-to-drain parasitics for drain efficiency enhancement. For frequency extension, the pole-stagger technique is adopted for the fundamental input and second-harmonic feedback voltage at the gate terminal. As a result, the proposed MPDC frequency doubler demonstrated a 19–45 GHz (81.25%) 3-dB instantaneous bandwidth, a 25–35 GHz (41.27%) 1-dB instantaneous bandwidth, a 23.2% peak drain efficiency (η<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>D</i></sub>) (>15% from 20 to 41 GHz), and a 17.7% peak total efficiency (η<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>total</roman></sub>) (>10% from 20 to 42 GHz) in 55-nm bulk CMOS technology.