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A pair of light waves – one zipping clockwise the other counterclockwise around a microscopic track – may hold the key to creating the world’s smallest gyroscope: one a fraction of the width of a human hair. By bringing this essential technology down to an entirely new scale, a team of applied physicists hopes to enable a new generation of phenomenally compact gyroscope-based navigation systems, among other intriguing applications.

“We have found a new detection scheme that may lead to the world’s smallest gyroscope,” said Li Ge, a physicist at the Graduate Center and Staten Island College, City University of New York. “Though these so-called optical gyroscopes are not new, our approach is remarkable both in its super-small size and potential sensitivity.”

Ge and his colleagues – physicist Hui Cao and her student Raktim Sarma, both at Yale University in New Haven, Connecticut – recently published their results in The Optical Society’s (OSA) new high-impact journal Optica.

More than creative learning toys, gyroscopes are indispensable components in a number of technologies, including inertial guidance systems, which monitor an object’s motion and orientation. Space probes, satellites, and rockets continuously rely on these systems for accurate flight control. But like so many other essential pieces of aerospace technology, weight is a perennial problem. According to NASA, it costs about $10,000 for every pound lifted into orbit, so designing essential components that are smaller and lighter is a constant struggle for engineers and project managers.

If the size of an optical gyroscope is reduced to just a fraction of a millimeter, as is presented in the new paper, it could then be integrated into optical circuit boards, which are similar to a conventional electric circuit board but use light to carry information instead of electric currents. This could drastically reduce the equipment cost in space missions, opening the possibility for a new generation of micro-payloads.

Putting a New Spin on Light-powered Gyroscopes

Quite different from mechanical gyroscopes, which are currently used on ships for stabilization and rockets for guidance, optical gyroscopes have no moving parts. Instead, dual light waves race around an optical cavity or fiber, constantly passing each other as they travel in opposite directions.

Traditional mechanical gyroscopes use Newton’s laws of motion to maintain stability and orientation. These same physics principles, however, do not apply to light, so measuring motion requires looking for telltale yet very subtle optical signals instead.

One such signal comes from the unusual property of light known as the Sagnac effect, which – put simply – creates a measurable interference pattern when light waves split and then recombine upon leaving a spinning system. Commercial optical gyroscopes build on this principle, with their sizes varying from that of a baseball to a basketball. They could be made much smaller, but measuring rotation would require a much greater level of sensitivity than is currently available.

Making a Gyroscope Out of Light

Traditionally, engineers have used two approaches to make optical gyroscopes, both based on the Sagnac effect. The first one uses an optical cavity – an engineered structure on a crystal – to confine light and the second one uses an optical fiber to guide light.

The second approach has, to date, been most practical because its sensitivity can be easily enhanced by using longer sections of optical fiber (some up to five kilometers long). These lengths of fiber would then be wrapped around an object about five centimeters in diameter, achieving a more manageable size. Though this system is sensitive to rotation, there are practical limits to how long the fiber can be and how small it can be wrapped before the fiber itself is damaged.

To go truly small, optical cavities seem to be the preferable option, where the Sagnac effect manifests as a subtle color change. The problem, however, has been that the sensitivity of this type of optical gyroscopes degrades as the cavity gets smaller.

“This issue was the roadblock that has hindered scientists from developing tiny optical gyroscopes,” noted Ge. “There have been several attempts to get around this limitation, but they could not get around the real problem, the Sagnac effect itself.”

The researchers were able to overcome this hurdle by using a very different principle based on far-field emission. Rather than directly measuring the color change of the light waves, the researchers determined that they could measure the pattern the light produced as it exited the cavity.

“That was our key innovation – finding a new signal with a much improved sensitivity to rotation,” said Ge. “Optical gyroscopes optimized to produce and detect this new signal, we found, could be about 10 microns across – smaller than the cross section of a human hair.”

The idea is similar to rotating an uncovered light bulb. You can’t see any direct spinning, but on small scales, the act of rotation itself causes a small but measurable relativistic effect – slightly bending space in and around the light source. This then almost imperceptibly distorts the pattern on the wall. If measured, however, the speed of rotation can be calculated from the degree of distorting.

Spinning the Gyroscope

To start the new optical gyroscope, light waves are first pumped into the optical cavity. This naturally produces light waves traveling in both clockwise and counterclockwise directions. This behavior is similar to plucking a guitar string in the middle, sending vibrations in both directions simultaneously.

By carefully designing the shape of the optical cavity, the researchers were able to control where both waves would exit. Normally, cavities are designed to trap light as long as possible. Here, the researchers needed to balance the light trapping properties of the cavity with the need for some light to escape to create a far-field emission pattern. This pattern is observed by placing a pair of camera-like detectors facing the cavity at different angles that move along with the cavity. This allows them to continuously monitor the pattern for distortions that would reveal the speed of rotation.

Though this only reveals one plane of motion, multiple such sensors at different orientations would be able to give a fully three-dimensional picture of how the object is moving.

Next Steps and Technology Development

According to the researchers, further studies are needed to take into consideration the possibility that many modes, or light paths, exist simultaneously in the cavity. Their far-field emission patterns may change in different ways, which causes a reduction of the sensitivity to rotation. The researchers are currently working on different methods to control this effect.

Pibond Oy, a specialty chemical manufacturer of advanced semiconductor solutions, today introduced its new product line of liquid spin-on metal oxide hardmask materials. Targeting 10nm node semiconductor processing, 3D NAND, power ICs as well as MEMS applications, this technology enables advanced device manufacturing through reduced cost of ownership (COO) and simplified processing.

With the ever-increasing demand for increased functionality in applications from personal computing to mobile to cloud storage to wearables, the semiconductor industry is targeting smaller and smaller nodes and in so doing has lived up to Gordon Moore’sprediction. However, the limits of current lithography processes and the uncertainty surrounding next generation approaches, compounded by their costs, have cast doubt on whether Moore’s law has finally run “out of steam.”

Pibond’s materials are designed to bridge this gap, providing continuity for existing high-end fabs, while maintaining compatibility for future technology roadmaps. These novel polymers represent the next generation of liquid spin-on hard mask products and are suitable for advanced lithographic patterning, 2.5/3D-IC packaging, as well as MEMS processing.

Pibond’s SAP 100 product line is based on patent pending organo-siloxane modified spin-on metal oxide thin films that are compatible with advanced photoresist lithography and other semiconductor etch processes. The product line offers tunable optical (n&k) properties matching critical requirements of advanced lithography. Furthermore, it shows extraordinary etch resistance in plasma etching processes even at very low film thicknesses. Unlike most conventional hard masks, the Pibond SAP hard mask is applied with low cost spin-on track equipment, enabling high throughput and lowering the overall COO. Importantly, it can be applied with process equipment common in both state-of-the-art and legacy fabs, thus eliminating the need for new and potentially capital-intensive equipment. Future product releases in the SAP-100 family will be directly photopatternable further decreasing process complexity and COO.

“As process throughput and the demand for ever increasing device performance continue to challenge the semiconductor industry, we are happy to announce this new class of products based on advanced metal oxide and siloxane polymers. Capable of extending the runway for existing lithography tools and processes, thereby lowering the operating costs of current and future fabs, they are also paving the way for the future as new technologies like EUV mature,” said Jonathan Glen, Chairman of Pibond. “As the industry demands new materials to meet the needs of EUV lithography, 3D memory, power ICs, image sensors, TSV and MEMS applications, Pibond is well placed to be a driving force in this transition.”

ULVAC, Inc. this week announced industry’s first low temperature PZT sputtering technology in mass production scale, enabling future advanced MEMS device integrated on CMOS which will be the mainstream of next generation MEMS devices.

Background

Today many sensors such as accelerometers, gyros, and pressure sensors are widely used inside high performance smart phones, tablet PCs, and automobiles enabling the “Smart society” representing the IoT world. The increasing demand and the key element to enable this functionality, is the piezoelectric MEMS (Micro Electro Mechanical Systems) device, using a piezoelectric thin film material called PZT (lead zirconate titanate, Pb(Zr,Ti)O3). Examples of applications in use are: actuators for auto focus lenses on digital cameras, and inkjet heads for printers.

The future holds that, higher performance, multi-functional and smaller piezoelectric MEMS devices for the next generation of advanced sensor technology is rapidly expanding its applications by the integration with CMOS devices. PZT, Piezo-electric MEMS is one of the most practical MEMS devices available today, however, the process temperature was an obstacle, to integrate the MEMS device directly onto a CMOS device. A CMOS device due to its nature, can only withstand a process temperature of 500 degrees C or lower. A typical crystallization temperature for a PZT thin film is 600 degrees C for sputtering and 700 degrees C for Sol-Gel.

ULVAC has developed world’s first unique innovative technology allowing integration of the piezoelectric MEMS device onto a CMOS device, thus achieving highest level piezoelectric performance, withstand voltage reliability, and cycle performance. This is accomplished by utilizing unique sputtering technology with process temperature below 500 degrees C.

Insight of the Technology

The piezoelectric device, using thin film PZT, is formed by five (5) layers which are: an adhesion layer, a lower electrode layer, a buffer layer, a piezoelectric (PZT) layer, and upper electrode layer. All the accumulated layers are formed sequentially, through one single sputtering system developed by ULVAC. This multi-chamber type sputtering system (model SME-200) allows for consistent process flow, optimizing each individual layer inside each process chamber respectively, achieving highly stable repeatability of the stacked layer performance, and also improving throughput, to that which is that is very suitable for mass production purposes.

Additionally this system is designed to achieve highly uniform and stable process utilizing 8-inch silicon wafers, the largest size substrate available for MEMS device mass production known today. Maximum seven (7) process chamber such as DC and RF magnetron sputtering chamber, RTA (Rapid Thermal Annealing) chamber to accelerate crystallization, and a load-lock chamber are utilized.

The PZT thin film is accumulated by crystal growth on a heated wafer. The sputtering chamber is specifically designed for dielectric material to allow stable deposition process and lead composition control, a character required for highly volatile materials such as PZT. The world’s highest PZT thin film performance level, in mass production is enabled, utilizing a new, low temperature process under 500 degrees C, and ULVAC unique process technology, for applying a buffer layer.

At this week’s OFC 2015, the largest global conference and exposition for optical communications, nanoelectronics research center imec, its associated lab at Ghent University (Intec), and Stanford University have demonstrated a compact germanium (Ge) waveguide electro-absorption modulator (EAM) with a modulation bandwidth beyond 50GHz. Combining state-of-the-art extinction ratio and low insertion loss with an ultra-low capacitance of just 10fF, the demonstrated EAM marks an important milestone for the realization of next-generation silicon integrated optical interconnects at 50Gb/s and beyond.

Future chip-level optical interconnects require integrated optical modulators with stringent requirements for modulation efficiency and bandwidth, as well as for footprint and thermal robustness. In the presented work, imec and its partners have improved the state-of-the-art for Ge EAMs on Si, realizing higher modulation speed, higher modulation efficiency and lower capacitance. This was obtained by fully leveraging the strong confinement of the optical and electrical fields in the Ge waveguides, as enabled in imec’s 200mm Silicon Photonics platform. The EAM was implemented along with various Si waveguide devices, highly efficient grating couplers, various active Si devices, and high speed Ge photodetectors, paving the way to industrial adoption of optical transceivers based on this device.

“This achievement is a milestone for realizing silicon optical transceivers for datacom applications at 50Gb/s and beyond,” stated Joris Van Campenhout, program director at imec. “We have developed a modulator that addresses the bandwidth and density requirements for future chip-level optical interconnects.”

Companies can benefit from imec’s Silicon Photonics platform (iSiPP25G) through established standard cells, or by exploring the functionality of their own designs in Multi-Project Wafer (MPW) runs. The iSiPP25G technology is available via ICLink services and MOSIS, a provider of low-cost prototyping and small volume production services for custom ICs.

University of Washington scientists have built a new nanometer-sized laser — using the thinnest semiconductor available today — that is energy efficient, easy to build and compatible with existing electronics.

Lasers play essential roles in countless technologies, from medical therapies to metal cutters to electronic gadgets. But to meet modern needs in computation, communications, imaging and sensing, scientists are striving to create ever-smaller laser systems that also consume less energy.

The ultra-thin semiconductor, which is about 100,000 times thinner than a human hair, stretches across the top of the photonic cavity. Credit: University of Washington

The ultra-thin semiconductor, which is about 100,000 times thinner than a human hair, stretches across the top of the photonic cavity. Credit:
University of Washington

The UW nanolaser, developed in collaboration with Stanford University, uses a tungsten-based semiconductor only three atoms thick as the “gain material” that emits light. The technology is described in a paper published in the March 16 online edition of Nature.

“This is a recently discovered, new type of semiconductor which is very thin and emits light efficiently,” said Sanfeng Wu, lead author and a UW doctoral candidate in physics. “Researchers are making transistors, light-emitting diodes, and solar cells based on this material because of its properties. And now, nanolasers.”

Nanolasers — which are so small they can’t be seen with the eye — have the potential to be used in a wide range of applications from next-generation computing to implantable microchips that monitor health problems. But nanolasers so far haven’t strayed far from the research lab.

Other nanolaser designs use gain materials that are either much thicker or that are embedded in the structure of the cavity that captures light. That makes them difficult to build and to integrate with modern electrical circuits and computing technologies.

The UW version, instead, uses a flat sheet that can be placed directly on top of a commonly used optical cavity, a tiny cave that confines and intensifies light. The ultrathin nature of the semiconductor — made from a single layer of a tungsten-based molecule — yields efficient coordination between the two key components of the laser.

The UW nanolaser requires only 27 nanowatts to kickstart its beam, which means it is very energy efficient.

Other advantages of the UW team’s nanolaser are that it can be easily fabricated, and it can potentially work with silicon components common in modern electronics. Using a separate atomic sheet as the gain material offers versatility and the opportunity to more easily manipulate its properties.

“You can think of it as the difference between a cell phone where the SIM card is embedded into the phone versus one that’s removable,” said co-author Arka Majumdar, UW assistant professor of electrical engineering and of physics.

“When you’re working with other materials, your gain medium is embedded and you can’t change it. In our nanolasers, you can take the monolayer out or put it back, and it’s much easier to change around,” he said.

The researchers hope this and other recent innovations will enable them to produce an electrically-driven nanolaser that could open the door to using light, rather than electrons, to transfer information between computer chips and boards.

The current process can cause systems to overheat and wastes power, so companies such as Facebook, Oracle, HP, Google and Intel with massive data centers are keenly interested in more energy-efficient solutions.

Using photons rather than electrons to transfer that information would consume less energy and could enable next-generation computing that breaks current bandwidth and power limitations. The recently proven UW nanolaser technology is one step toward making optical computing and short distance optical communication a reality.

“We all want to make devices run faster with less energy consumption, so we need new technologies,” said co-author Xiaodong Xu, UW associate professor of materials science and engineering and of physics. “The real innovation in this new approach of ours, compared to the old nanolasers, is that we’re able to have scalability and more controls.”

Still, there’s more work to be done in the near future, Xu said. Next steps include investigating photon statistics to establish the coherent properties of the laser’s light.

Silicon Labs, a provider of semiconductor and software solutions for the Internet of Things (IoT) and Digi-Key, a developer of electronic component selection, availability and delivery, today announced an IoT design contest for pioneering developers who want to create connected “things” that will help make the world a smarter, more connected and energy-friendly place. Co-sponsored by Silicon Labs and Digi-Key, the “Your IoT Connected World” design contest is open to inventors of all skill levels, from professional embedded developers and seasoned makers to electronics enthusiasts.

The contest runs now through July 17, with three winners to be announced on August 3, 2015. Visitors to the www.YourIoTContest.com site will vote to decide on 15 finalists, and expert judges from Silicon Labs and Digi-Key will choose the three winners. Each winner will select the Silicon Labs components they need (microcontrollers, wireless chips, sensors, boards and more – valued up to $10,000) to bring their prize-winning IoT ideas to market as commercially viable products.

“The silicon and software technology needed to make ‘your IoT’ a reality is available today, and it’s up to pioneering developers like you to create the next IoT innovations that will help save time and energy, enhance health and security, and improve the quality of life for people everywhere,” said Peter Vancorenland, vice president of engineering and IoT solutions at Silicon Labs. “This is your chance to bring your groundbreaking IoT ideas to market, enabled by Silicon Labs development tools and kickstarted by $10,000 in Silicon Labs components.”

“Whether designers are solving an existing problem or creating a totally new invention, ideas are limited only by the developer’s imagination,” said David Sandys, director of technical marketing for Digi-Key. “Winning IoT designs may include innovations like connected home devices, smart appliances, lighting control systems, wearable technology, security systems, wireless sensor networks and much more.”

To get started, simply visit www.YourIoTContest.com. All IoT designs must contain a Silicon Labs microcontroller (MCU) product. Each contestant must submit photos or a brief video overview of their IoT product design. Silicon Labs offers a wide array of 8-bit and 32-bit MCUs, wireless ICs, interface chips, optical and environmental sensors, and development tools for IoT applications, all available through Digi-Key. To help simplify the evaluation, design and prototyping process, Silicon Labs’ Simplicity Studio development platform can be downloaded at no charge at www.silabs.com/simplicity-studio.

The competition is open to contestants in selected countries in the Americas and EMEA including Austria, Belgium, Brazil, Canada (excluding Quebec), the Czech Republic, Denmark, Finland, France, Germany, Hungary, Ireland, Israel, Italy, Mexico, Norway, Poland, Portugal, Spain, Sweden, Turkey, the United Kingdom and the United States.

Creating large amounts of polymer nanofibers dispersed in liquid is a challenge that has vexed researchers for years. But engineers and researchers at North Carolina State University and one of its start-up companies have now reported a method that can produce unprecedented amounts of polymer nanofibers, which have potential applications in filtration, batteries and cell scaffolding.

In a paper published online in Advanced Materials, the NC State researchers and colleagues from industry, including NC State start-up company Xanofi, describe the method that allows them to fabricate polymer nanofibers on a massive scale.

The method – fine-tuned after nearly a decade of increasing success in producing micro- and nanoparticles of different shapes – works as simply as dropping liquid solution of a polymer in a beaker containing a spinning cylinder. Glycerin – a common and safe liquid that has many uses – is used to shear the polymer solution inside the beaker along with an antisolvent like water. When you take out the rotating cylinder, says Dr. Orlin Velev, Invista Professor of Chemical and Biomolecular Engineering at NC State and the corresponding author of the paper describing the research, you find a mat of nanofibers wrapped around it.

When they first started investigating the liquid shearing process, the researchers created polymer microrods, which could have various useful applications in foams and consumer products.

“However, while investigating the shear process we came up with something strange. We discovered that these rods were really just pieces of ‘broken’ fibers,” Velev said. “We didn’t quite have the conditions set perfectly at that time. If you get the conditions right, the fibers don’t break.”

NC State patented the liquid shear process in 2006 and in a series of subsequent patents while Velev and his colleagues continued to work to perfect the process and its outcome. First, they created microfibers and nanoribbons as they investigated the process.

“Microfibers, nanorods and nanoribbons are interesting and potentially useful, but you really want nanofibers,” Velev said. “We achieved this during the scaling up and commercialization of the technology.”

Velev engaged with NC State’s Office of Technology Transfer and the university’s TEC (The Entrepreneurship Collaborative) program to commercialize the discoveries. They worked with the experienced entrepreneur Miles Wright to start a company called Xanofi to advance the quest for nanofibers and the most efficient way to make mass quantities of them.

“We can now create kilograms of nanofibers per hour using this simple continuous flow process, which when scaled up becomes a ‘nanofiber gusher,'” Velev said. “Depending on the concentrations of liquids, polymers and antisolvents, you can create multiple types of nanomaterials of different shapes and sizes.”

“Large quantities are paramount in nanomanufacturing, so anything scalable is important,” said Wright, the CEO of Xanofi and a co-author on the paper. “When we produce the nanofibers via continuous flow, we get exactly the same nanofibers you would get if you were producing small quantities of them. The fabrication of these materials in liquid is advantageous because you can create truly three-dimensional nanofiber substrates with very, very high overall surface area. This leads to many enhanced products ranging from filters to cell scaffolds, printable bioinks, battery separators, plus many more.”

Graphene quantum dots made from coal, introduced in 2013 by the Rice University lab of chemist James Tour, can be engineered for specific semiconducting properties in either of two single-step processes.

Vials hold solutions with graphene quantum dots that fluoresce in different colors depending on the dots' size. Techniques to produce the dots in specific sizes using coal as a source were developed at Rice University. Credit: Tour Group/Rice University

Vials hold solutions with graphene quantum dots that fluoresce in different colors depending on the dots’ size. Techniques to produce the dots in specific sizes using coal as a source were developed at Rice University.
Credit: Tour Group/Rice University

In a new study this week in the American Chemical Society journal Applied Materials & Interfaces, Tour and colleagues demonstrated fine control over the graphene oxide dots’ size-dependent band gap, the property that makes them semiconductors. Quantum dots are semiconducting materials that are small enough to exhibit quantum mechanical properties that only appear at the nanoscale.

Tour’s group found they could produce quantum dots with specific semiconducting properties by sorting them through ultrafiltration, a method commonly used in municipal and industrial water filtration and in food production.

The other single-step process involved direct control of the reaction temperature in the oxidation process that reduced coal to quantum dots. The researchers found hotter temperatures produced smaller dots, which had different semiconducting properties.

Tour said graphene quantum dots may prove highly efficient in applications ranging from medical imaging to additions to fabrics and upholstery for brighter and longer-lasting colors.

“Quantum dots generally cost about $1 million per kilogram and we can now make them in an inexpensive reaction between coal and acid, followed by separation. And the coal is less than $100 per ton.”

The dots in these experiments all come from treatment of anthracite, a kind of coal. The processes produce batches in specific sizes between 4.5 and 70 nanometers in diameter.

Graphene quantum dots are photoluminescent, which means they emit light of a particular wavelength in response to incoming light of a different wavelength. The emitted light ranges from green (smaller dots) to orange-red (larger dots). Because the emitted color also depends on the dots’ size, this property can also be tuned, Tour said. The lab found quantum dots that emit blue light were easiest to produce from bituminous coal.

The researchers suggested their quantum dots may also enhance sensing, electronic and photovoltaic applications. For instance, catalytic reactions could be enhanced by manipulating the reactive edges of quantum dots. Their fluorescence could make them suitable for metal or chemical detection applications by tuning to avoid interference with the target materials’ emissions.

EV Group (EVG), a supplier of wafer bonding and lithography equipment for the MEMS, nanotechnology and semiconductor markets, today introduced two new configurations to its EVG 580 ComBond series of automated high-vacuum covalent wafer bonding systems. Addressing the needs of universities and R&D institutes, and high-volume manufacturing (HVM) requirements, respectively, both system configurations achieve electrically conductive and oxide-free bonds of materials with different lattice constants and coefficients of thermal expansion at room temperature.

Applications that demand room-temperature bonding of substrates with very different material properties and that are supported by the EVG580 ComBond series include advanced engineered substrates, power devices, stacked solar cells and emerging technologies such as silicon photonics.

The new entry-level EVG580 ComBond system for universities and R&D institutes comes with one cassette station or manual load port as well as a single-arm robot, supporting up to three process modules. The EVG580 ComBond HVM system can be configured with two cassette stations or an equipment front-end module with up to four cassettes for continuous mode operation, as well as comes with a dual-arm robot to support up to six process modules for maximum throughput.

Both new ComBond system configurations, as well as the standard system that can accommodate up to five process modules, are built on a modular platform supporting wafers up to 200mm in diameter. In addition to one or more bond chambers, the systems feature a dedicated ComBond Activation Module (CAM), which provides advanced surface preparation by directing energized particles to the substrate surface to achieve a contamination-free and oxide-free bond interface. The systems operate in a high-vacuum-process environment with base pressures in the range of 5×10-8 mbar, which prevents re-oxidation of the treated wafers prior to the bonding step.

“The EVG580 ComBond system with its standard five-module configuration, which was launched last autumn, has already demonstrated its capabilities with multiple R&D partners and customers,” stated Dr. Thomas Glinsner, corporate product management director at EV Group. “With the new three-module system, we will now make this breakthrough technology available to universities and smaller R&D institutes, which often are at the forefront of pioneering advanced electronic materials and device research, such as heterogeneous integration of compound semiconductors for silicon photonics and other leading-edge applications. All ComBond systems can be further customized to address specific application development needs, such as with special metrology modules utilizing free ports of the high-vacuum handling.”

wafer bonding ev group

A team of Columbia Engineering researchers has invented a technology–full-duplex radio integrated circuits (ICs)–that can be implemented in nanoscale CMOS to enable simultaneous transmission and reception at the same frequency in a wireless radio. Up to now, this has been thought to be impossible: transmitters and receivers either work at different times or at the same time but at different frequencies. The Columbia team, led by Electrical Engineering Associate Professor Harish Krishnaswamy, is the first to demonstrate an IC that can accomplish this. The researchers presented their work at the International Solid-State Circuits Conference (ISSCC) in San Francisco on February 25.

“This is a game-changer,” says Krishnaswamy. “By leveraging our new technology, networks can effectively double the frequency spectrum resources available for devices like smartphones and tablets.”

CoSMIC (Columbia high-Speed and Mm-wave IC) Lab full-duplex transceiver IC that can be implemented in nanoscale CMOS to enable simultaneous transmission and reception at the same frequency in a wireless radio. Image courtesy Jin Zhou and Harish Krishnaswamy, Columbia Engineering

CoSMIC (Columbia high-Speed and Mm-wave IC) Lab full-duplex transceiver IC that can be implemented in nanoscale CMOS to enable simultaneous transmission and reception at the same frequency in a wireless radio.
Image courtesy Jin Zhou and Harish Krishnaswamy, Columbia Engineering

In the era of Big Data, the current frequency spectrum crisis is one of the biggest challenges researchers are grappling with and it is clear that today’s wireless networks will not be able to support tomorrow’s data deluge. Today’s standards, such as 4G/LTE, already support 40 different frequency bands, and there is no space left at radio frequencies for future expansion. At the same time, the grand challenge of the next-generation 5G network is to increase the data capacity by 1,000 times.

So the ability to have a transmitter and receiver re-use the same frequency has the potential to immediately double the data capacity of today’s networks. Krishnaswamy notes that other research groups and startup companies have demonstrated the theoretical feasibility of simultaneous transmission and reception at the same frequency, but no one has yet been able to build tiny nanoscale ICs with this capability.

“Our work is the first to demonstrate an IC that can receive and transmit simultaneously,” he says. “Doing this in an IC is critical if we are to have widespread impact and bring this functionality to handheld devices such as cellular handsets, mobile devices such as tablets for WiFi, and in cellular and WiFi base stations to support full duplex communications.”

The biggest challenge the team faced with full duplex was canceling the transmitter’s echo. Imagine that you are trying to listen to someone whisper from far away while at the same time someone else is yelling while standing next to you. If you can cancel the echo of the person yelling, you can hear the other person whispering.

“If everyone could do this, everyone could talk and listen at the same time, and conversations would take half the amount of time and resources as they take right now,” explains Jin Zhou, Krishnaswamy’s PhD student and the paper’s lead author. “Transmitter echo or ‘self-interference’ cancellation has been a fundamental challenge, especially when performed in a tiny nanoscale IC, and we have found a way to solve that challenge.”

Krishnaswamy and Zhou plan next to test a number of full-duplex nodes to understand what the gains are at the network level. “We are working closely with Electrical Engineering Associate Professor Gil Zussman’s group, who are network theory experts here at Columbia Engineering,” Krishnaswamy adds. “It will be very exciting if we are indeed able to deliver the promised performance gains.”