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Spectrum Slicer. MEMS for RF Oscillators & Filters. David Giles & Curtis Mayberry December 7 th , 2012. Some Motivation. Oscillators On-chip integration High frequencies Bandpass Filters Many different filters, small area Narrow passbands (High Q) Good for channel select Applications
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Spectrum Slicer MEMS for RF Oscillators & Filters David Giles & Curtis Mayberry December 7th, 2012
Some Motivation • Oscillators • On-chip integration • High frequencies • Bandpass Filters • Many different filters, small area • Narrow passbands (High Q) • Good for channel select • Applications • RF Receivers (e.g. cellphones) • Cognitive Radio (spectrum hopping)
Piezoelectric Contour-Mode Resonator • Frequency range: 19 to 656 MHz • Q’s of around 4000 • Motional resistance: 50 to 700 Ω • Lithographically defined center frequencies • Width vs. length-extensional modes [Piazza, et al. 2006]
Laterally-Excited SiBAR • Motional resistance of 35 Ω • 100 MHz center frequency • Aluminum nitride now sputtered on sidewall • Use of d33 coefficient [Tabrizian, et al. 2011]
Bandpass Filter • Capacitive coupling by intrinsic capacitances [Zuo, et al. 2010]
Broadband Tunable TIA for Oscillators • Low-power broadband current preamp • 76 dBΩ constant gain up to 1.7 GHz • Demonstrated operation with 1 GHz, 750 Ω, and a 724 MHz, 150 Ωresonators
MEMS Challenges • Balancing greater thickness versus a distorted modeshape to maximize electromechanical coupling • Achieving low motional impedance • Designing an effective model • Learning COMSOL
Electroded Layers • The two pictures below show the two layers of Molybdenum electrodes and overall structure of the device
1 GHz Resonator • Q of 10,000 (1/3 of the theoretical maximum for Silicon) was assumed • One-port admittance simulated for half-resonator • Simulated only half of the device for faster results (while maintaining accuracy) • Dimensions • Height = 2um • Length = 20um • Width = 3.9um (counting AlN)
RLC Extraction – 1 GHz Resonator • fo = 986.5 MHz • R = 1 V / Total Current = 1 / 3.7mA = 267.3Ω • L = Q*R/ (2*π*fo) = 431.2uH • C = 1 / (L*(2*π*fo)2 = 60.36aF • Cft = eo*er*A/d = 10*8.854e-12*(2e-6*20e-6*2 + 20e-6*3.9e-6) / 1e-6 = 14fF
100 MHz Resonator Design • 98.14601 MHz • length extensional mode • Dimensions: • W = 40um • L = 400um • H = 20um • TAlN = 2um Cftt =2.2pF Cm =254.7aF R=1.1kΩ L =11mH
Simulated Bandpass Filter • 2nd order BPF • LCs as given for the 1 GHz resonator • Ccap = 30fF, Rterm = 250 Ω • 3dB bandwidth = 1 MHz • 20dB SF = 3 • Passband Ripple = 0.3 dB • IL = 2dB
Biasing: Current source • Supply insensitive due to cascode • Provides 3v dc bias to TIA. • Provides 15uA current bias that is used to generate voltage bias
Input Stage • Current amplifier + current to voltage conversion ‖
Trans-impedance Amplifier • Current mirror amplifier: 1:10 current amplification • Common source second stage with feedback • Shunt-shunt feedback to increase bandwidth • Total phase shift = 0°as required
TIA Open Loop Response • 76.47 dBΩ peak transimpedance gain • 115 MHz 3dB bandwidth
Packaging • Multi-chip-module • Easily integrated with other RF dies (LNA, PA, etc.) • MEMs and interface dies will be bonded to MCM directly • As more components are designed and integrated on one die, other solutions may become more notable • Can be integrated with existing technology
Ladder Filter Design “Reciprocal Mixing”
References 1] B. Razavi, RF Microelectronics, Second Edition, Prentice Hall 2011. [2] R. Aigner, “Innovative RF Filter Technologies: Gaurdrails for the Wireless Data Highway,” Microwave Product Digest. June 2007. [3] S. Pourkamali, G. K. Ho, and F. Ayazi, “Low-impedance VHF and UHF capacitive silicon bulk acoustic wave resonators - Part I: Concept and Fabrication” IEEE Transactions on Electron Devices, May 2007, Vol. 54, No. 8, Aug. 2007, pp. 2017-2023. [4] S. Pourkamali, G. K. Ho, and F. Ayazi, “Low-impedance VHF and UHF capacitive silicon bulk acoustic wave resonators - Part II: Measurement and Characterization,” IEEE Transactions on Electron Devices, Vol. 54, No. 8, Aug. 2007, pp. 2024-2030. [5] Z. Hao, S. Pourkamali, and F. Ayazi, “VHF Single Crystal Silicon Elliptic Bulk-Mode Capacitive Disk Resonators; Part I: Design and Modeling,” IEEE Journal of Microelectromechanical Systems, Vol. 13, No. 6, Dec. 2004, pp. 1043-1053. [6] S. Pourkamali, Z. Hao, and F. Ayazi, “VHF Single Crystal Silicon Elliptic Bulk-Mode Capacitive Disk Resonators; Part II: Implementation and Characterization,” IEEE Journal of Microelectromechanical Systems, Vol. 13, No. 6, Dec. 2004, pp. 1054-1062. [7] H. MiriLavassani, R. Abdolvand, and F. Ayazi, “A 500MHz Low Phase Noise AlN-on-Silicon Reference Oscillator,” Proc. IEEE Custom Integrated Circuits Conference (CICC 2007), Sept. 2007, pp. 599-602. [8] H.M. Lavasani, W. Pan, B. Harrington, R. Abdolvand, and F. Ayazi, “A 76dBOhm, 1.7 GHz, 0.18um CMOS Tunable Transimpedance Amplifier Using Broadband Current Pre-Amplifier for High Frequency Lateral Micromechanical Oscillators,” IEEE International Solid State Circuits Conference (ISSCC 2010), San Francisco, CA, Jan. 2010, pp. 318-320 [9] B. Razavi, “Cognitive Radio Design Challenges and Techniques,” IEEE Journal of Solid-State Circuits, vol. 45, pp.1542-1553, Aug. 2010. [10] J. Garrido, “Biosensors and Bioelectronics Lecture 10,”Walter SchottkyInstitut Center for Nanotechnology and Nanomaterials. http://www.wsi.tum.de/Portals/0/Media/Lectures/20082/98f31639-f453-466d-bbc2-a76a95d8dead/BiosensorsBioelectronics_lecture10.pdf [11] S. Pourkamali, R. Abdolvand, and F. Ayazi, “A 600kHz Electrically Coupled MEMS Bandpass Filter,” Proc. IEEE International Micro Electro Mechanical Systems Conference (MEMS‘03), Kyoto, Japan, Jan. 2003, pp. 702-705. [12] R. Tabrizian and F. Ayazi, "Laterally Excited Silicon Bulk Acoustic Resonator with Sidewall AlN," International Conference on Solid-State Sensors, Acutators and Microsystems (Transducers), Beijing, China, June 2011. [13] C. Zuo, N. Sinha, G. Piazza, “Very High Frequency Channel-Select MEMS Filters based on Self-Coupled Piezoelectric AlN Contour-Mode Resonators”, Sensors and Actuators, A Physical, vol. 160, no. 1-2, pp. 132-140, May 2010.
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