Flicker Phase-Noise Reduction Using Gate-Drain Phase Shift in Transformer-Based Oscillators

Abstract

This article presents a wide-band suppression technique of flicker phase noise (PN) by means of a gate-drain phase shift in a transformer-based complementary oscillator. We identify that after naturally canceling its second-harmonic voltage by the complementary operation itself, third-harmonic current entering the capacitive path is now the main cause of asymmetry in the rising and falling edges, leading to the 1/f noise upconversion. A complete 1/f 3 PN analysis for the transformer-based complementary oscillator is discussed. By tuning gate-drain capacitance ratio, a specific phase-shift range is introduced at the gate and drain nodes of the cross-coupled pair to mitigate the detrimental effects of ill-behaved third-harmonic voltage, thus lowering the flicker PN. To further reduce the area and improve the PN in the thermal region, we introduce a new triple-8-shaped transformer. Fabricated in 22-nm FDSOI, the prototype occupies a compact area of 0.01mm2 and achieves 1/f3 PN corner of 70kHz, PN of-110dBc/Hz at 1MHz offset, figure-of-merit (FoM) of-182dB at 9GHz, and 39% tuning range (TR). It results in the best FoM with normalized TR and area (FoMTA) of-214dB at 1MHz offset.