A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset

Baset Mesgari; Saeed Saeedi; Reinhard Feger; Horst Zimmermann

doi:10.1109/Austrochip67945.2025.11183682

A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset

Baset Mesgari^*, Saeed Saeedi^*, Reinhard Feger^*, Horst Zimmermann^*

^*Corresponding author for this work

Institute for Communications Engineering and RF-Systems

Research output: Chapter in Book/Report/Conference proceeding › Conference proceedings › peer-review

Abstract

A modified source-coupled relaxation oscillator with dynamic biasing feedback is presented as a reference clock. The proposed topology achieves a close-in phase noise of -72.9 dBc/Hz at a 1 kHz offset. By suppressing the effective impulse sensitivity function of the tail transistors, the technique significantly reduces flicker noise upconversion into the oscillator’s 1/f3 phase noise. Experimental results demonstrate a close-in figure of merit improvement of approximately 4 dB over previously reported comparator-based RC relaxation and source-coupled relaxation oscillator designs. Implemented in a 0.35 µm CMOS process, the oscillator operates at 2.65 MHz while consuming only 13.2 µW from a 3 V supply.

Original language	English
Title of host publication	2025 Austrochip Workshop on Microelectronics (Austrochip)
Publisher	IEEE
Pages	17-20
Number of pages	4
ISBN (Electronic)	979-8-3315-5477-4
ISBN (Print)	979-8-3315-5478-1
DOIs	https://doi.org/10.1109/Austrochip67945.2025.11183682
Publication status	Published - 25 Sept 2025
Event	2025 Austrochip Workshop on Microelectronics (Austrochip) - Linz, Austria Duration: 24 Sept 2025 → 25 Sept 2025

Publication series

Name	Proceedings of the Austrian Workshop on Microelectronics, Austrochip
ISSN (Print)	2689-8152

Conference

Conference	2025 Austrochip Workshop on Microelectronics (Austrochip)
Period	24.09.2025 → 25.09.2025

Fields of science

202033 Radar technology
202019 High frequency engineering
202 Electrical Engineering, Electronics, Information Engineering
202037 Signal processing
202029 Microwave engineering

JKU Focus areas

Digital Transformation

Access to Document

10.1109/Austrochip67945.2025.11183682

https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11183682

Cite this

Mesgari, B., Saeedi, S., Feger, R., & Zimmermann, H. (2025). A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset. In 2025 Austrochip Workshop on Microelectronics (Austrochip) (pp. 17-20). Article 11183682 (Proceedings of the Austrian Workshop on Microelectronics, Austrochip). IEEE. https://doi.org/10.1109/Austrochip67945.2025.11183682

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title = "A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset",

abstract = "A modified source-coupled relaxation oscillator with dynamic biasing feedback is presented as a reference clock. The proposed topology achieves a close-in phase noise of -72.9 dBc/Hz at a 1 kHz offset. By suppressing the effective impulse sensitivity function of the tail transistors, the technique significantly reduces flicker noise upconversion into the oscillator{\textquoteright}s 1/f3 phase noise. Experimental results demonstrate a close-in figure of merit improvement of approximately 4 dB over previously reported comparator-based RC relaxation and source-coupled relaxation oscillator designs. Implemented in a 0.35 µm CMOS process, the oscillator operates at 2.65 MHz while consuming only 13.2 µW from a 3 V supply.",

keywords = "Phase noise, Timing jitter, Sensitivity, Power demand, CMOS process, Performance metrics, Topology, 1/f noise, Transistors, Clocks",

author = "Baset Mesgari and Saeed Saeedi and Reinhard Feger and Horst Zimmermann",

year = "2025",

month = sep,

day = "25",

doi = "10.1109/Austrochip67945.2025.11183682",

language = "English",

isbn = "979-8-3315-5478-1",

series = "Proceedings of the Austrian Workshop on Microelectronics, Austrochip",

publisher = "IEEE",

pages = "17--20",

booktitle = "2025 Austrochip Workshop on Microelectronics (Austrochip)",

note = "2025 Austrochip Workshop on Microelectronics (Austrochip) ; Conference date: 24-09-2025 Through 25-09-2025",

}

Mesgari, B, Saeedi, S, Feger, R & Zimmermann, H 2025, A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset. in 2025 Austrochip Workshop on Microelectronics (Austrochip)., 11183682, Proceedings of the Austrian Workshop on Microelectronics, Austrochip, IEEE, pp. 17-20, 2025 Austrochip Workshop on Microelectronics (Austrochip), 24.09.2025. https://doi.org/10.1109/Austrochip67945.2025.11183682

A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset. / Mesgari, Baset; Saeedi, Saeed; Feger, Reinhard et al.
2025 Austrochip Workshop on Microelectronics (Austrochip). IEEE, 2025. p. 17-20 11183682 (Proceedings of the Austrian Workshop on Microelectronics, Austrochip).

Research output: Chapter in Book/Report/Conference proceeding › Conference proceedings › peer-review

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T1 - A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset

AU - Mesgari, Baset

AU - Saeedi, Saeed

AU - Feger, Reinhard

AU - Zimmermann, Horst

PY - 2025/9/25

Y1 - 2025/9/25

N2 - A modified source-coupled relaxation oscillator with dynamic biasing feedback is presented as a reference clock. The proposed topology achieves a close-in phase noise of -72.9 dBc/Hz at a 1 kHz offset. By suppressing the effective impulse sensitivity function of the tail transistors, the technique significantly reduces flicker noise upconversion into the oscillator’s 1/f3 phase noise. Experimental results demonstrate a close-in figure of merit improvement of approximately 4 dB over previously reported comparator-based RC relaxation and source-coupled relaxation oscillator designs. Implemented in a 0.35 µm CMOS process, the oscillator operates at 2.65 MHz while consuming only 13.2 µW from a 3 V supply.

AB - A modified source-coupled relaxation oscillator with dynamic biasing feedback is presented as a reference clock. The proposed topology achieves a close-in phase noise of -72.9 dBc/Hz at a 1 kHz offset. By suppressing the effective impulse sensitivity function of the tail transistors, the technique significantly reduces flicker noise upconversion into the oscillator’s 1/f3 phase noise. Experimental results demonstrate a close-in figure of merit improvement of approximately 4 dB over previously reported comparator-based RC relaxation and source-coupled relaxation oscillator designs. Implemented in a 0.35 µm CMOS process, the oscillator operates at 2.65 MHz while consuming only 13.2 µW from a 3 V supply.

KW - Phase noise

KW - Timing jitter

KW - Sensitivity

KW - Power demand

KW - CMOS process

KW - Performance metrics

KW - Topology

KW - 1/f noise

KW - Transistors

KW - Clocks

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UR - https://www.scopus.com/pages/publications/105019741004

U2 - 10.1109/Austrochip67945.2025.11183682

DO - 10.1109/Austrochip67945.2025.11183682

M3 - Conference proceedings

SN - 979-8-3315-5478-1

T3 - Proceedings of the Austrian Workshop on Microelectronics, Austrochip

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EP - 20

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PB - IEEE

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Y2 - 24 September 2025 through 25 September 2025

ER -

A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset

Abstract

Publication series

Conference

Fields of science

JKU Focus areas

Access to Document

Other files and links

Christian Doppler Laboratory for DistributedMicrowave- and Terahertz-Systems for Sensors and Data Links

Cite this

A CMOS Source-Coupled Relaxation Oscillator Achieving Close-in Phase Noise of -72.9 dBc/Hz at a 1 kHz Offset

Abstract

Publication series

Conference

Fields of science

JKU Focus areas

Access to Document

Other files and links

Projects

Christian Doppler Laboratory for DistributedMicrowave- and Terahertz-Systems for Sensors and Data Links

Cite this