A Distributed Stubs Technique to Mitigate Flicker Noise Upconversion in a mm-Wave Rotary Traveling-Wave Oscillator

Abstract

A rotary traveling-wave oscillator (RTWO) has an ability to generate multiple phases at millimeter-wave (mmW) frequencies while achieving low phase noise (PN). Unfortunately, due to the practically unavoidable transmission line (TL) dispersion, which causes the higher-order harmonics to travel faster than the fundamental, RTWOs suffer from flicker noise upconversion. In this article, we propose a "distributed stubs" technique to mitigate this mechanism in which tuning capacitors placed on the TL stubs away from the maintaining amplifiers will slow down the travel speed of higher-order harmonics relative to the fundamental, thus lowering the phase shifts due to the TL dispersion. We further provide a comprehensive analysis of the flicker noise upconversion mechanism due to the TL dispersion. The proposed 26.2-30-GHz RTWO is implemented in 22-nm fully depleted silicon-on-insulator (FD-SOI) CMOS with eight differential phases. At 30 GHz, it achieves PN of −107.6 and −128.9 dBc/Hz at 1-and 10-MHz offsets, respectively. This translates into figures-of-merit (FoMs) of 184.2 and 185.4 dB, respectively, for a single phase. The proposed architecture consumes 20 mW from 0.8-V supply. It achieves a flicker PN corner of 180 kHz, which is an orderof-magnitude better than currently achievable by state-of-the-art mmW RTWOs.

A 19.1–25.5-GHz Compact Dual-Mode Rotary Traveling-Wave Oscillator With 195.4-dBc/Hz FoM

“…A single-core RTWO is divided into N segments to support N differential phases [25]. The oscillation frequency is determined by the following equation:…”

“…It is not easy for coupled LCOs to generate more than four phases. Compared with conventional coupled LCOs, rotary traveling-wave oscillator (RTWO) has the advantage of generating multiple phases in limited area [20]- [25]. However, the reported RTWOs lack effective wideband tuning method and are less attractive to multistandard wireless communication systems.…”