A 28-GHz Fractional-N Frequency Synthesizer with Reference and Frequency Doublers for 5G Mobile Communications in 65nm CMOS

Hanli LIU  Teerachot SIRIBURANON  Kengo NAKATA  Wei DENG  Ju Ho SON  Dae Young LEE  Kenichi OKADA  Akira MATSUZAWA  

IEICE TRANSACTIONS on Electronics   Vol.E101-C   No.4   pp.187-196
Publication Date: 2018/04/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E101.C.187
Type of Manuscript: Special Section PAPER (Special Section on Solid-State Circuit Design — Architecture, Circuit, Device and Design Methodology)
5G communications,  CMOS,  28GHz,  fractional-N frequency synthesizer,  phase noise,  spur,  

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This paper presents a 27.5-29.6GHz fractional-N frequency synthesizer using reference and frequency doublers to achieve low in-band and out-of-band phase-noise for 5G mobile communications. A consideration of the baseband carrier recovery circuit helps estimate phase noise requirement for high modulation scheme. The push-push amplifier and 28GHz balun help achieving differential signals with low out-of-band phase noise while consuming low power. A charge pump with gated offset as well as reference doubler help reducing PD noise resulting in low in-band phase noise while sampling loop filter helps reduce spurs. The proposed synthesizer has been implemented in 65nm CMOS technology achieving an in-band and out-of-band phase noise of -78dBc/Hz and -126dBc/Hz, respectively. It consumes only a total power of 33mW. The jitter-power figure-of-merit (FOM) is -231dB which is the highest among the state of the art >20GHz fractional-N PLLs using a low reference clock (<200MHz). The measured reference spurs are less than -80dBc.