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!
handling and a Q >50,000 crucial in making the spec.
Arraying for Impedance <480W at 72MHz!
coupled resonator arrays automatically align resonator frequencies to allow
output summation for low impedance and higher power handling.
better resolution of the above, click on the above, then click again to
the links at the upper left for detailed information.
Micromechanical Resonator Wins
Best Paper Award at the 2005 IEEE Int. Frequency Control Symposium!
to Yu-Wei Lin for winning the Best Frequency Control Paper Award at the 2005
IEEE Int. Frequency Control Symposium.
Clock Overview Paper Wins the Jack Raper Award at the
2005 IEEE Int. Solid-State Circuits Conference!
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
Read this for an
overview on vibrating RF MEMS.
Oscillator Wins 2004 UFFC
Symposium Best Frequency Control Paper Award!
to Seungbae Lee for winning the Best Frequency Control Paper Award at the 2004
IEEE Ultrasonics, Ferroelectrics, and Frequency Control 50th Anniv. Joint
Resonator Work Wins 2003 IEDM Best Paper Award!
to Yuan Xie for winning the 2003 Int. Electron Devices Meeting Roger A. Haken
Best Student Paper Award.
Prof. Nguyen's Research
Focus: (a quick
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.
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.
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.
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.