Low Phase Noise 14-Bit Digitally Controlled CMOS Quadrature Ring Oscillator

Ramesh K. POKHAREL  Prapto NUGROHO  Awinash ANAND  Abhishek TOMAR  Haruichi KANAYA  Keiji YOSHIDA  

IEICE TRANSACTIONS on Electronics   Vol.E96-C   No.2   pp.262-269
Publication Date: 2013/02/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E96.C.262
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Microwaves, Millimeter-Waves
sub-feedback,  phase noise,  ring oscillator,  digitally controlled oscillator,  quadrature outputs,  

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High phase noise is a common problem in ring oscillators. Continuous conduction of the transistor in an analog tuning method degrades the phase noise of ring oscillators. In this paper, a digital control tuning which completely switches the transistors on and off, and a 1/f noise reduction technique are employed to reduce the phase noise. A 14-bit control signal is employed to obtain a small frequency step and a wide tuning range. Furthermore, multiphase ring oscillator with a sub-feedback loop topology is used to obtain a stable quadrature outputs with even number of stages and to increase the output frequency. The measured DCO has a frequency tuning range from 554 MHz to 2.405 GHz. The power dissipation is 112 mW from 1.8 V power supply. The phase noise at 4 MHz offset and 2.4 GHz center frequency is -134.82 dBc/Hz. The FoM is -169.9 dBc/Hz which is a 6.3 dB improvement over the previous oscillator design.