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

• Published in: IEEE journal of solid-state circuits 2021-06, Vol.56 (6), p.1745-1760
• Main Authors: Shehata, Mohamed Atef, Keaveney, Michael, Staszewski, Robert Bogdan
• Format: Article
• Language: English
• Subjects: 1f noise; 30 GHz; Bandwidth; CMOS; Dispersion; distributed oscillator; fifth generation (5G); Flicker; flicker noise upconversion; Frequency conversion; fully depleted silicon-on-insulator (FD-SOI); Harmonic analysis; Higher harmonics; Jitter; low phase noise (PN); Millimeter waves; millimeter-wave (mmW or mm-Wave); Noise; phase sensitivity function; rotary traveling-wave oscillator (RTWO); transmission line (TL) dispersion; Transmission lines; Tuning; Upconversion
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2020.3044278

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 order-of-magnitude better than currently achievable by state-of-the-art mmW RTWOs.