A Study of Stability and Phase Noise of Tail Capacitive-Feedback VCOs

Ahmed MUSA; Kenichi OKADA; Akira MATSUZAWA

doi:10.1587/transele.E96.C.577

A Study of Stability and Phase Noise of Tail Capacitive-Feedback VCOs

Ahmed MUSA, Kenichi OKADA, Akira MATSUZAWA

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Capacitive feedback VCOs use capacitors that are connected from the output node to the gate of the tail transistor that acts as a current source. Using such feedback results in modulating the current that is used by the oscillator and therefore changes its cyclostationary noise properties which results in a lower output phase noise. This paper presents a mathematical study of capacitive feedback VCOs in terms of stability and phase noise enhancement to confirm stability and to explain the enhancement in phase noise. The derived expression for the phase noise shows an improvement of 4.4 dB is achievable by using capacitive feedback as long as the VCO stays in the current limited region. Measurement results taken from an actual capacitive feedback VCO implemented in a 65 nm CMOS process also agrees with the analysis and simulation results which further validates the given analysis.

Publication: IEICE TRANSACTIONS on Electronics Vol.E96-C No.4 pp.577-585

Publication Date: 2013/04/01

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Online ISSN: 1745-1353

DOI: 10.1587/transele.E96.C.577

Type of Manuscript: Special Section PAPER (Special Section on Solid-State Circuit Design—Architecture, Circuit, Device and Design Methodology)

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Ahmed MUSA, Kenichi OKADA, Akira MATSUZAWA, "A Study of Stability and Phase Noise of Tail Capacitive-Feedback VCOs" in IEICE TRANSACTIONS on Electronics, vol. E96-C, no. 4, pp. 577-585, April 2013, doi: 10.1587/transele.E96.C.577.
Abstract: Capacitive feedback VCOs use capacitors that are connected from the output node to the gate of the tail transistor that acts as a current source. Using such feedback results in modulating the current that is used by the oscillator and therefore changes its cyclostationary noise properties which results in a lower output phase noise. This paper presents a mathematical study of capacitive feedback VCOs in terms of stability and phase noise enhancement to confirm stability and to explain the enhancement in phase noise. The derived expression for the phase noise shows an improvement of 4.4 dB is achievable by using capacitive feedback as long as the VCO stays in the current limited region. Measurement results taken from an actual capacitive feedback VCO implemented in a 65 nm CMOS process also agrees with the analysis and simulation results which further validates the given analysis.
URL: https://globals.ieice.org/en_transactions/electronics/10.1587/transele.E96.C.577/_p

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@ARTICLE{e96-c_4_577,
author={Ahmed MUSA, Kenichi OKADA, Akira MATSUZAWA, },
journal={IEICE TRANSACTIONS on Electronics},
title={A Study of Stability and Phase Noise of Tail Capacitive-Feedback VCOs},
year={2013},
volume={E96-C},
number={4},
pages={577-585},
abstract={Capacitive feedback VCOs use capacitors that are connected from the output node to the gate of the tail transistor that acts as a current source. Using such feedback results in modulating the current that is used by the oscillator and therefore changes its cyclostationary noise properties which results in a lower output phase noise. This paper presents a mathematical study of capacitive feedback VCOs in terms of stability and phase noise enhancement to confirm stability and to explain the enhancement in phase noise. The derived expression for the phase noise shows an improvement of 4.4 dB is achievable by using capacitive feedback as long as the VCO stays in the current limited region. Measurement results taken from an actual capacitive feedback VCO implemented in a 65 nm CMOS process also agrees with the analysis and simulation results which further validates the given analysis.},
keywords={},
doi={10.1587/transele.E96.C.577},
ISSN={1745-1353},
month={April},}

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TY - JOUR
TI - A Study of Stability and Phase Noise of Tail Capacitive-Feedback VCOs
T2 - IEICE TRANSACTIONS on Electronics
SP - 577
EP - 585
AU - Ahmed MUSA
AU - Kenichi OKADA
AU - Akira MATSUZAWA
PY - 2013
DO - 10.1587/transele.E96.C.577
JO - IEICE TRANSACTIONS on Electronics
SN - 1745-1353
VL - E96-C
IS - 4
JA - IEICE TRANSACTIONS on Electronics
Y1 - April 2013
AB - Capacitive feedback VCOs use capacitors that are connected from the output node to the gate of the tail transistor that acts as a current source. Using such feedback results in modulating the current that is used by the oscillator and therefore changes its cyclostationary noise properties which results in a lower output phase noise. This paper presents a mathematical study of capacitive feedback VCOs in terms of stability and phase noise enhancement to confirm stability and to explain the enhancement in phase noise. The derived expression for the phase noise shows an improvement of 4.4 dB is achievable by using capacitive feedback as long as the VCO stays in the current limited region. Measurement results taken from an actual capacitive feedback VCO implemented in a 65 nm CMOS process also agrees with the analysis and simulation results which further validates the given analysis.
ER -