andrew yee

Office of Media Relations
University of California-Los Angeles

Media Contacts:
Melissa Abraham, (310) 206-0540

FOR IMMEDIATE RELEASE: Monday, April 16, 2007

UCLA Engineers Set World Record for High-Frequency Submillimeter Waves

Researchers at the UCLA Henry Samueli School of Engineering and Applied
Science have achieved a new world record in high-frequency submillimeter
waves. The record-setting 324-gigahertz frequency was accomplished using a
voltage-controlled oscillator in a 90-nanometer complementary metal-oxide
semiconductor (CMOS) integrated circuit, a technology used in chips such as
microprocessors.

The signal generator, which produces frequencies nearly 70 percent faster
than other CMOS oscillators, paves the way for a new generation of
submillimeter devices that could someday be used in high-resolution sensors
on spacecraft, and here on Earth in a new class of highly integrated and
lightweight imagers that could literally cut through fog and see through
clothing fabrics. And because frequency ultimately means bandwidth, "the
higher frequency increases the available bandwidth," said M.C. Frank Chang,
UCLA professor of electrical engineering, who leads the research team. That
greater bandwidth translates into faster communication speeds.

With traditional 90-nanometer CMOS circuit approaches, it is virtually
impossible to generate usable submillimeter signals with a frequency higher
than about 190 GHz. That's because conventional oscillator circuits are
nonlinear systems in which increases in frequency are accompanied by a
corresponding loss in gain or efficiency and an increase in noise, making
them unsuitable for practical applications.

Chang, who also is director of UCLA Engineering's High Speed Electronics
Laboratory, and researchers Daquan Huang and Tim LaRocca skirted the issues
using a technological sleight of hand -- and some unique ****og signal
processing.

The researchers first generated a voltage-controlled CMOS oscillator, or
CMOS VCO, operating at a fundamental frequency of 81GHz with phase-shifted
outputs at 0, 90, 180 and 270
degrees, respectively. By linearly superimposing these four (or quadruple)
rectified phase-shifted outputs in real time, they ultimately generated a
waveform with a resultant oscillation frequency that is four times the
fundamental frequency, or 324 GHz. This new frequency generation method, in
principle, has high DC-to-RF conversion efficiency (up to 8 percent) and has
low phase noise, comparable to that of the constituent fundamental
oscillation signal.

"When you go back to the fundamental math and physics, you find that you can
do this and not pay much of a price. That's the beauty of it," Chang said.
"If you use digital signal processing, you can synthesize this and
synthesize that, but you pay the price for it with a loss of energy."

The measurement test of the 324-GHz signal was conducted by engineers Lorene
Samoska and Andy Fung of NASA's Jet Propulsion Laboratory in Pasadena, which
has facilities to test these high-frequency ranges. JPL and NASA are
particularly interested in submillimeter technology because
submillimeter-range wavelengths are ideal for deep-space remote sensing --
there is no atmosphere in space to dampen the signals. Higher frequency
signals, in turn, produce higher resolution images. "You can see better,"
Chang said.

Chang and Huang, in collaboration with JPL colleagues, have jointly applied
for government grants to use the technology to design lightweight, low-power
and highly integrated signal generators that can produce signals at
frequencies up to 600 GHz. Applications for these high-frequency VCOs
include imaging systems for both commercial and future space missions.

Creating 600-GHz signals requires a relatively straightforward modification
of the circuit -- either by increasing the fundamental frequency of the VCO
or increasing the number of superimposed oscillator outputs (using eight or
16 instead of four).

"Because the algorithm has been validated, we know that we can achieve these
frequencies," Chang says.

For example, if quadruple 85-GHz VCO outputs are used, the resulting output
frequency would be 340 GHz. That frequency is something of a Holy Grail to
the commercial aerospace industry and the military because it represents a
"window" in our atmosphere where there is very little attenuation of
submillimeter signals. (Essentially, they are invisible to the air.)

Normally, millimeter-range waves excite the atomic and molecular bonds in
water, oxygen, carbon dioxide and other molecules in the atmosphere, and the
gases absorb the waves. Signals at 340 GHz, however, "sneak through," Chang
said, and can propagate long distances.

"One result is that waves of these frequencies can see through the fog,
which is of interest to commercial aerospace companies," he said. Chang
estimates that he and his colleagues will be able to produce the 340-GHz
signals within the next six months

Another application of the high-frequency CMOS VCOs of interest to the
United States military is in submillimeter wavelength imaging.

"Because the wavelength is submillimeter, you may image through people's
clothing," Chang said. "For example, it would be possible to remotely view
if some civilian walking up to you has plastic explosives hidden under his
coat."

CMOS technology makes future submillimeter-wave devices easily integrated
with advanced microprocessors on-chip and can be very lightweight, so these
sensors would be portable. "Foot soldiers could backpack them into the
battle zone," Chang said.

About the UCLA Henry Samueli School of Engineering and Applied Science

Established in 1945, the UCLA Henry Samueli School of Engineering and
Applied Science offers 28 academic and professional degree programs,
including an interdepartmental graduate degree program in biomedical
engineering. Ranked among the top 10 engineering schools at public
universities nationwide, the school is home to seven multimillion-dollar
interdisciplinary research centers in space exploration, wireless sensor
systems, nanomanufacturing and defense technologies, which are funded by top
national and professional agencies. For more information, visit
http://www.engineer.ucla.edu .