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Oscillator Research

Overview

The Feng Research Group studies tiny vibrating mechanical devices called MEMS and NEMS oscillators. Our goal is to understand how networks of these oscillators interact and how their collective behavior can be used to solve complex optimization problems. Today, such problems are typically solved using digital processors. While powerful, these systems can require large amounts of energy and time when many interacting variables are involved. Alternative approaches based on physical systems are being explored, but many rely on simulations or electronic circuits that are difficult to scale.

Our work develops networks of micro- and nanoscale mechanical oscillators that influence each other through controlled coupling. Building on earlier work demonstrating stable, high-frequency oscillators in materials such as silicon and aluminum nitride, we now focus on synchronization and collective dynamics in oscillator arrays. If successful, this research could enable new computing platforms that solve certain optimization problems faster and more efficiently, while also advancing MEMS oscillator technologies for sensing and timing applications.

Featured Publications:

A Programmable Sustaining Amplifier for Flexible Multimode MEMS-Referenced Oscillators

This paper presents a programmable single-chip sustaining amplifier for MEMS oscillators with integrated low-noise amplification, tunable filtering, automatic level control, and feedthrough cancellation. Fabricated in 0.5 μm CMOS and tested with 10–90 kHz resonators, the system achieves a 20 dBc/Hz reduction in close-in phase noise (10 Hz offset) using high-Q (~13,000) single-crystal devices versus low-Q (~320) polysilicon. These results demonstrate effective background cancellation, phase optimization, and stable frequency locking for low-noise MEMS oscillator applications.

Parametric Frequency Divider based Ising Machines

This paper presents a new class of Ising machines based on coupled parametric frequency dividers (PFDs), eliminating the need for strong injection or DC bias and enabling nanowatt-level power per spin. A 4-node prototype solves Max-Cut problems at 600 nW per spin—two orders of magnitude lower power than state-of-the-art SHIL-based designs—while achieving fast synchronization and reduced time-to-solution.

A Self-Sustained Frequency Comb Oscillator via Tapping Mode Comb-Drive Resonator Integrated with a Feedback ASIC

In this conference paper, we demonstrate the first reconfigurable self-sustained MEMS oscillator capable of generating either a single stable tone or a frequency comb with tunable spacing. The system integrates a single-crystal SOI comb-drive resonator with a programmable CMOS sustaining amplifier, enabling operation across linear, nonlinear, and tapping regimes. By tuning DC bias and loop gain, the oscillator produces controllable combs with ~0.8–2.6 kHz spacing, highlighting a compact and versatile platform for multi-frequency signal generation.

References:

Journal Papers

  • Kaisar T, Habermehl ST, Casilli N, Mandal S, Rais-Zadeh M, Roukes ML, Shaw SW, Cassella C, Feng PXL*, “Synchronization Dynamics of MEMS Oscillators with Sub-Harmonic Injection Locking (SHIL) for Emulating Artificial Ising Spins”, Journal of Microelectromechanical Systems 34, Accepted, In Press (2025). DOI:
  • Casilli N, Kim S, Hussein H, Tetro R, Colombo L, Rinaldi, Feng PXL, Alù A, Cassella C, “Ising Dynamics for Programmable Threshold Sensing in Wireless Devices”, Nature Electronics 8, 529-536 (2025).  DOI: https://doi.org/10.1038/s41928-025-01392-4
  • Casilli N+, Kaisar T+, Colombo L, Ghosh S, Feng PXL*, Cassella C*, “Parametric Frequency Divider based Ising Machines”, Physical Review Letters 132, 147301 (2024). DOI: https://doi.org/10.1103/PhysRevLett.132.147301 
  • Kaisar T, Yousuf SMEH, Lee J, Qamar A, Rais-Zadeh M, Mandal S, Feng PXL*, “Five Low-Noise Stable Oscillators Referenced to the Same Multimode AlN/Si MEMS Resonator”, IEEE Transactions on Ultrasonics, Ferroelectrics, & Frequency Control (T-UFFC), 70, 1213-1228, (2023). DOI: https://doi.org/10.1109/TUFFC.2023.3312159
  • Lee J, Feng PXL*, “Self-Sustaining MoS2 Nanomechanical Oscillators and Feedback Cooling”, Applied Physics Letters 119, 243506 (2021). DOI: https://doi.org/10.1063/5.0063079
  • Islam MS, Singh SK, Lee JS, Xie Y, Zorman CA, Feng PXL, Mandal S*, “A Programmable Sustaining Amplifier for Flexible Multimode MEMS-Referenced Oscillators”, IEEE Transactions on Circuits & Systems I: Regular Papers (2018). DOI: https://doi.org/10.1109/TCSI.2018.2880675
  • Islam MS, Wei R, Lee JS, Xie Y, Mandal S*, Feng PXL*, “A Temperature-Compensated Single-Crystal Silicon-on-Insulator (SOI) MEMS Oscillator with a CMOS Amplifier Chip”, Micromachines 9, 559 (2018). DOI: https://doi.org/10.3390/mi9110559
  • Zheng XQ, Lee JS, Rafique S, Karim MR, Han L, Zhao H, Zorman CA, Feng PXL*, “β-Ga2O3 NEMS Oscillator for Real-Time Middle Ultraviolet (MUV) Light Detection”, IEEE Electron Device Letters 39, 1230-1233 (2018). DOI: https://doi.org/10.1109/LED.2018.2850776
  • Feng PXL*, “Tuning in to a Graphene Oscillator”, Nature Nanotechnology 8, 897-898 (2013). DOI: https://doi.org/10.1038/nnano.2013.268
  • Feng PXL, White CJ, Hajimiri A, Roukes ML*, “A Self-Sustaining Ultrahigh-Frequency Nanoelectromechanical Oscillator”, Nature Nanotechnology 3, 342-346 (2008). [Featured with News & Views]. [90] (This work was later reported in public media such as NanotechWeb.org, etc.) DOI: https://doi.org/10.1038/nnano.2008.125

Conference Papers

  • Kaisar T, Yousuf SMEH, Casilli N, Rais-Zadeh M, Mandal S, Cassella C, Feng PXL, “Demonstration of Artificial Spin States Using Sub-Harmonic Injection Locking in AlN-on-Si Length-Extensional Mode MEMS Self-Sustaining Oscillator”, Proc. 37th IEEE Int. Conf. on Micro Electro Mechanical Systems (MEMS 2024), 186-189, Austin TX, January 21-25 (2024). DOI: https://doi.org/10.1109/MEMS58180.2024.10439574
  • Kaisar T, Dehghanzadeh P, Feng PXL, Mandal S, “Digitally Programmable CMOS Feedback ASIC for Network of Coupled Electromechanical Oscillators”, Proc. 56th IEEE International Symposium on Circuits & Systems (ISCAS 2023) (5 pages), Monterey, CA, USA, May 21-25 (2023). DOI: https://doi.org/10.1109/ISCAS46773.2023.10182172
  • Casilli N, Kaya O, Kaisar T, Davaji B, Feng PXL, Cassella C, “Nonvolatile State Configuration of Nano-Watt Parametric Ising Spins through Ferroelectric Hafnium Zirconium Oxide MEMS Varactors”, Proc. 36th IEEE Int. Conf. on Micro Electro Mechanical Systems (MEMS 2023), 511-514, Munich, Germany & Online (Hybrid), January 15-19 (2023). DOI: https://doi.org/10.1109/MEMS49605.2023.10052601
  • Kaisar T, Yousuf SMEH, Lee J, Qamar A, Rais-Zadeh M, Mandal S, Feng PXL, “Multiple Stable Oscillators Referenced to the Same Multimode AlN/Si MEMS Resonator with Mode-Dependent Phase Noise and Frequency Stability”, Proc. of the 68th IEEE International Electron Devices Meeting (IEDM 2022), Paper No. 16.3, 378-381, San Francisco, CA, USA, December 3-7 (2022). DOI: https://doi.org/10.1109/IEDM45625.2022.10019478
  • Wei R, Lee JS, Mei T, Xie Y, Islam MS, Mandal S, Feng PXL, “A Self-Sustained Frequency Comb Oscillator via Tapping Mode Comb-Drive Resonator Integrated with a Feedback ASIC”, Proc. 32nd IEEE Int. Conf. on Micro Electro Mechanical Systems (MEMS 2019), 165-168, Seoul, Korea, January 27-31 (2019). DOI: https://doi.org/10.1109/MEMSYS.2019.8870745
  • Zheng XQ, Lee JS, Rafique S, Karim RM, Han L, Zhao H, Zorman CA, Feng PXL, “Towards Real-Time Middle Ultraviolet (MUV) Light Detection by β-Ga2O3 NEMS Oscillators”, Digest of Tech. Papers, the 18th Solid-State Sensors, Actuators, and Microsystems Workshop (Hilton Head’18), 92-93, Hilton Head Island, SC, June 3-7 (2018). DOI: https://doi.org/10.31438/trf.hh2018.25
  • Khanmohammad H, Wang P, Babecki C, Feng PXL, Mandal S, “A Programmable CMOS Feedback IC for Reconfigurable MEMS-Referenced Oscillators”, Proc. of the 14th IEEE International New Circuits & Systems Conference (NEWCAS), (4 pages), Vancouver, BC, Canada, June 26-29 (2016). DOI: https://doi.org/10.1109/NEWCAS.2016.7604795
  • Tang H, Jia H, Feng PXL, “High-Q Silicon Carbide (SiC) Micromechanical Self-Sustained Feedback Oscillator Operating in Liquid”, Proc. 29th IEEE Int. Conf. on Micro Electro Mechanical Systems (MEMS 2016), 714-717, Shanghai, China, January 24-28 (2016). DOI: https://doi.org/10.1109/MEMSYS.2016.7421727
  • Wang ZH, Wang P, Lee JS, Liu C-C, Feng PXL, “Towards Real-Time Methane (CH4) Capture and Detection by Nanoparticle-Enhanced Silicon Carbide Trampoline Oscillators”, Tech. Digest, the 18th International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers 2015), 432-435, Anchorage, Alaska, June 21-25 (2015). DOI: https://doi.org/10.1109/TRANSDUCERS.2015.7180953
  • Zamani H, Feng PXL, “Design of a 2.5µW, 1GHz Low Phase Noise Pierce Oscillator with Nanowire NEMS Resonator”, Digest of Tech. Papers, IEEE International Frequency Control Symposium (IFCS’13) at the Joint UFFC, EFTF and PFM Symposia, 948-951, Prague, Czech Republic, July 21-25 (2013). DOI: https://doi.org/10.1109/EFTF-IFC.2013.6702309