Clark T.-C. Nguyen
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Must Read Papers:

1.51-GHz with Q >10,000 Even in Air!
A result of purposely impedance-mismatching a polydiamond disk with its polysilicon stem.


1.2-GHz with Q = 14,600!

Who says diamond is needed to get Q >10,000 at GHz frequencies? With the right "hollow-disk" ring design, polysilicon can do even better than diamond.



60-MHz Wine-Glass Disk Oscillator Makes the GSM Reference Oscillator Spec!
Higher power handling and a Q >50,000 crucial in making the spec.



Arraying for Impedance <480W at 72MHz!
Mechanically coupled resonator arrays automatically align resonator frequencies to allow output summation for low impedance and higher power handling.



Clark T.-C. Nguyen


Dept. of Electrical Engineering & Computer Sciences

University of California, Berkeley

574 Cory Hall

Berkeley, California 94720
Tel: (510) 642-6251

Fax: (510) 643-6637



The Latest Award Winning Papers:

Solid-Gap Vibrating Micromechanical Resonator Wins Best Paper Award at the 2005 IEEE Int. Frequency Control Symposium!
Congratulations to Yu-Wei Lin for winning the Best Frequency Control Paper Award at the 2005 IEEE  Int. Frequency Control Symposium.


Chip-Scale Atomic Clock Overview Paper Wins the Jack Raper Award at the 2005 IEEE Int. Solid-State Circuits Conference!
Congratulations to all those in the CSAC program (which Prof. Nguyen ran while at DARPA), especially John Kitching from NIST, who co-authored this paper.


Vibrating RF MEMS Wins Best Invited Paper Award at the 2004 IEEE Custom Integrated Circuits Conference!
Read this for an overview on vibrating RF MEMS.


Resonator Array Oscillator Wins 2004 UFFC Symposium Best Frequency Control Paper Award!
Congratulations to Seungbae Lee for winning the Best Frequency Control Paper Award at the 2004 IEEE Ultrasonics, Ferroelectrics, and Frequency Control 50th Anniv. Joint Conf.


Ext. Wine-Glass Resonator Work Wins 2003 IEDM Best Paper Award!
Congratulations to Yuan Xie for winning the 2003 Int. Electron Devices Meeting Roger A. Haken Best Student Paper Award.



Recent News Items:

05/21/12 3 papers presented at the 2012 Int. Frequency Control Symposium in Baltimore, Maryland. Follow the Research link for pdf's of the papers.

7/1/12 Ph.D. student Li-Wen Hung graduates -- congrats! Li-Wen is now working at Invensense, in California.

Prof. Nguyen's Research Focus: (a quick summary)

Today’s wireless transceivers are generally designed under a near mandate to minimize or eliminate, in as much as possible, the use of high-Q passives. The reasons for this are quite simple: cost and size. Specifically, the ceramic filters, SAW filters, quartz crystals, and now FBAR filters, capable of achieving the Q’s from 500-10,000 needed for RF and IF bandpass filtering and frequency generation functions, are all off-chip components that must interface with transistor functions at the board-level, taking up a sizable amount of the total board volume, and comprising a sizable fraction of the parts and assembly cost.

For this reason, much of the recent mainstream research in wireless design has focused on the use of direct-conversion receiver architectures to remove the IF filter, and the use of  integrated inductor technologies to remove some of the off-chip L’s used for bias and matching networks. Although these methods can lower cost, they often do so at the expense of increased transistor circuit complexity and more stringent requirements on circuit performance (e.g., dynamic range), both of which degrade somewhat the robustness and power efficiency of the overall system. In addition, the removal of the IF filter does little to appease the impending needs of future multi-band reconfigurable handsets that will likely require high-Q RF filters in even larger quantities—perhaps one set for each wireless standard to be addressed. A quick look at next generation wireless architectures clearly shows that it is the high-Q RF filters, not the IF filter, that must be addressed. In the face of this need, an option to reinsert high Q components without the size and cost penalties of the past would be most welcome.

Prof. Nguyen's research focuses on the use of microelectromechanical systems (MEMS) technology to make available on-chip devices with Q's in the thousands that not only alleviate the above problem, but can potentially revolutionize the design of wireless circuits. In particular, Nguyen's Micromechanical Resonator Research Group, formerly at the University of Michigan and now at the University of California at Berkeley, has recently utilized MEMS technology to demonstrate on-chip vibrating micromechanical resonators operating past GHz frequencies with Q’s in excess of 10,000; 60-MHz micromechanical resonator self-sustained oscillators that satisfy the phase noise specifications for GSM communication reference oscillators with substantially lower power consumption; tunable on-chip micromechanical capacitors with Q's exceeding 300; RF MEMS switches with record low insertion loss and high linearity; and micromechanical mixer-filter devices that combine mixer and high-Q filtering functions all into one low-loss, passive device.

The advent of such devices, together with technologies to integrate them together with transistor circuits all onto a single chip, may now not only provide an attractive solution to the multi-band transceiver needs described above, but might also enable a paradigm-shift in transceiver design where the advantages of high-Q (e.g., in filters and oscillators) are emphasized, rather than suppressed . In particular, like transistors, micromechanical elements can be used in large quantities without adding significant cost. This not only brings more robust superheterodyne architectures back into contention, but also encourages modifications to take advantage of a new abundance in low loss ultra-high-Q frequency shaping at GHz frequencies. For example, an RF channel-select filter bank may now be possible, capable of eliminating not only out-of-band interferers, but also out-of-channel interferers, and in so doing, relaxing the dynamic range requirements of the LNA and mixer, and the phase noise requirements of the local oscillator, to the point of perhaps allowing complete transceiver implementations using very low cost transistor circuits (e.g., perhaps eventually even organic circuits). Transistorless RF front-ends are even conceivable, and if achievable, could potentially eliminate battery drain by future RF front-ends, without sacrificing the overall receiver noise figure.

Research on topics pursuant to realizing the above vision are presently underway in Prof. Nguyen's research group at the University of California at Berkeley. In particular, his Micromechanical Resonator Research Group is presently investigating extension of the frequency range of micromechanical signal processors (filters and oscillators) into the upper-UHF range, exploring the possibility of all-mechanical radio, developing merged circuit/microstructure technologies, studying physical phenomena that influence the frequency stability of micro- and nano-scale mechanical resonators, exploring novel architectures for single-chip transceivers for military and commercial applications using MEMS technologies, developing automatic generation codes for mechanical filter design, and designing and implementing novel, completely monolithic integrated sensors. For more information, please follow the links in this website.


Last Updated Tuesday, Aug. 7, 2012.

Contents copyright @ 2012. All rights reserved.

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