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 analog 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.
Melissa Abraham | EurekAlert!
Silicon solar cell of ISFH yields 25% efficiency with passivating POLO contacts
08.12.2016 | Institut für Solarenergieforschung GmbH
Robot on demand: Mobile machining of aircraft components with high precision
06.12.2016 | Fraunhofer IFAM
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Physics and Astronomy
08.12.2016 | Health and Medicine
08.12.2016 | Life Sciences