A repository & source of cutting edge news about emerging terahertz technology, it's commercialization & innovations in THz devices, quality & process control, medical diagnostics, security, astronomy, communications, applications in graphene, metamaterials, CMOS, compressive sensing, 3d printing, and the Internet of Nanothings. NOTHING POSTED IS INVESTMENT ADVICE! REPOSTED COPYRIGHT IS FOR EDUCATIONAL USE.
Screens may be larger on smartphones now, but nearly every other component is designed to be thinner, flatter and tinier than ever before. The engineering requires a shift from shapely, and bulky lenses to the development of miniaturized, two-dimensional metalenses. They might look better, but do they work better?
A team of Japan-based researchers says yes, thanks to a solution they published on July 7th in Applied Physics Express.
The researchers previously developed a low-reflection metasurface—an ultra-thin interface that can manipulate electromagnetic waves—specifically to control terahertz waves. These waves overlap millimeter waves and infrared waves, and, while they can transmit a significant amount of data, they easily attenuate in the atmosphere.
The technology may not be suitable for long-range wireless communications, but could improve short-range data exchanges, such as residential internet speeds, said paper author Takehito Suzuki, associate professor in the Institute of Engineering at Tokyo University of Agriculture and Technology. According to Suzuki, the researchers have taken a step toward such application developments by using their metasurface to craft the world's best ultra-short metalens that collimates to align an optical system with a distance of only one millimeter. The metalens is capable of increasing transmitted power by three at the far field, where the signal strength typically weakens.
"Terahertz flat optics based on our originally developed low-reflection metasurface with a high-refractive index can offer attractive two-dimensional optical components for the manipulation of terahertz waves," Suzuki said.
The challenge was whether the collimating lens, which converts approximately spherical-shaped terahertz waves to aligned terahertz waves, made with the metasurface, could be mounted closely to the electronics—called a resonant tunneling diode—that transmits terahertz waves at the right frequency and in the right direction. The minimal distance between the diode and the metalens is the necessary ingredient in current and future electronic devices, Suzuki said.
"We resolved this problem," Suzuki said. "We integrated a fabricated collimating metalens made with our original metasurface with a resonant tunneling diode at a distance of one millimeter." Measurements verify that the collimating metalens integrated with the resonant tunneling diode enhances the directivity to three times that of a single resonant tunneling diode.
The researchers tuned their device to 0.3 terahertz, a band at a higher frequency than the one used for 5G wireless communications. The manipulation of higher-frequency electromagnetic waves allows the upload and download of huge amounts of data in 6G wireless communications, according to Suzuki.
"The 0.3 terahertz band is a promising candidate for 6G offering advanced cyber-physical systems," Suzuki said. "And our presented collimating metalens can be simply integrated with various terahertz continuous-wave sources to accelerate the growth of emerging terahertz industry such as 6G wireless communications."
On the electromagnetic spectrum, terahertz light is located between infrared radiation and microwaves. It holds enormous potential for tomorrow's technologies: Among other things, it might succeed 5G by enabling extremely fast mobile communications connections and wireless networks. The bottleneck in the transition from gigahertz to terahertz frequencies has been caused by insufficiently efficient sources and converters. A German-Spanish research team with the participation of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now developed a material system to generate terahertz pulses much more effectively than before. It is based on graphene, i.e., a super-thin carbon sheet, coated with a metallic lamellar structure. The research group presented its results in the journal ACS Nano.
Some time ago, a team of experts working on the HZDR accelerator ELBE were able to show that graphene can act as a frequency multiplier: When the two-dimensional carbon is irradiated with light pulses in the low terahertz frequency range, these are converted to higher frequencies. Until now, the problem has been that extremely strong input signals, which in turn could only be produced by a full-scale particle accelerator, were required to generate such terahertz pulses efficiently."This is obviously impractical for future technical applications," explains the study's primary author Jan-Christoph Deinert of the Institute of Radiation Physics at HZDR. "So, we looked for a material system that also works with a much less violent input, i.e., with lower field strengths."
For this purpose, HZDR scientists, together with colleagues from the Catalan Institute of Nanoscience and Nanotechnology (ICN2), the Institute of Photonic Sciences (ICFO), the University of Bielefeld, TU Berlin and the Mainz-based Max Planck Institute for Polymer Research, came up with a new idea: the frequency conversion could be enhanced enormously by coating the graphene with tiny gold lamellae, which possess a fascinating property: "They act like antennas that significantly amplify the incoming terahertz radiation in graphene," explains project coordinator Klaas-Jan Tielrooij from ICN2. "As a result, we get very strong fields where the graphene is exposed between the lamellae. This allows us to generate terahertz pulses very efficiently."
Surprisingly effective frequency multiplication
To test the idea, team members from ICN2 in Barcelona produced samples: First, they applied a single graphene layer to a glass carrier. On top, they vapor-deposited an ultra-thin insulating layer of aluminum oxide, followed by a lattice of gold strips. The samples were then taken to the TELBE terahertz facility in Dresden-Rossendorf, where they were hit with light pulses in the low terahertz range (0.3 to 0.7 THz). During this process, the experts used special detectors to analyze how effectively the graphene coated with gold lamellae can multiply the frequency of the incident radiation.
"It worked very well," Sergey Kovalev is happy to report. He is responsible for the TELBE facility at HZDR. "Compared to untreated graphene, much weaker input signals sufficed to produce a frequency-multiplied signal." Expressed in numbers, just one-tenth of the originally required field strength was enough to observe the frequency multiplication. And at technologically relevant low field strengths, the power of the converted terahertz pulses is more than a thousand times stronger thanks to the new material system. The wider the individual lamellae and the smaller the areas of graphene that are left exposed, the more pronounced the phenomenon. Initially, the experts were able to triple the incoming frequencies. Later, they attained even larger effects -- fivefold, sevenfold, and even ninefold increases in the input frequency.
Compatible with chip technology
This offers a very interesting prospect, because until now, scientists have needed large, complex devices such as accelerators or large lasers to generate terahertz waves. Thanks to the new material, it might also be possible to achieve the leap from gigahertz to terahertz purely with electrical input signals, i.e., with much less effort. "Our graphene-based metamaterial would be quite compatible with current semiconductor technology," Deinert emphasizes. "In principle, it could be integrated into ordinary chips." He and his team have proven the feasibility of the new process -- now implementation in specific assemblies may become possible.
The potential applications could be vast: Since terahertz waves have higher frequencies than the gigahertz mobile communications frequencies used today, they could be used to transmit significantly more wireless data -- 5G would become 6G. But the terahertz range is also of interest to other fields -- from quality control in industry and security scanners at airports to a wide variety of scientific applications in materials research, for example.
Jan-Christoph Deinert, David Alcaraz Iranzo, Raúl Pérez, Xiaoyu Jia, Hassan A. Hafez, Igor Ilyakov, Nilesh Awari, Min Chen, Mohammed Bawatna, Alexey N. Ponomaryov, Semyon Germanskiy, Mischa Bonn, Frank H.L. Koppens, Dmitry Turchinovich, Michael Gensch, Sergey Kovalev, Klaas-Jan Tielrooij. Grating-Graphene Metamaterial as a Platform for Terahertz Nonlinear Photonics. ACS Nano, 2020; DOI: 10.1021/acsnano.0c08106
Radiation of varying frequencies emanate from a leaky waveguide at different angles. This rainbow of frequencies is the basis for a link discovery system for future terahertz data networks.CREDIT Mittleman Lab / Knightly Lab
PROVIDENCE, R.I. [Brown University] -- When someone opens a laptop, a router can quickly locate it and connect it to the local Wi-Fi network. That ability is a basic element of any wireless network known as link discovery, and now a team of researchers has developed a means of doing it with terahertz radiation, the high-frequency waves that could one day make for ultra-fast wireless data transmission.
Because of their high frequency, terahertz waves can carry hundreds of times more data than the microwaves used to carry our data today. But that high frequency also means that terahertz waves propagate differently than microwaves. Whereas microwaves emanate from a source in an omni-directional broadcast, terahertz waves propagate in narrow beams.
"When you're talking about a network that's sending out beams, it raises a whole myriad of questions about how you actually build that network," said Daniel Mittleman, a professor in Brown's School of Engineering. "One of those questions is how does an access point, which you can think of as a router, find out where client devices are in order to aim a beam at them. That's what we're thinking about here."
In a paper published in Nature Communications, researchers from Brown and Rice University showed that a device known as a leaky waveguide can be used for link discovery at terahertz frequencies. The approach enables link discovery to be done passively, and in one shot.
The concept of a leaky waveguide is simple. It's just two metal plates with a space between them where radiation can propagate. One of the plates has a narrow slit cut into it, which allows a little bit of the radiation to leak out. This new research shows the device can be used for link discovery and tracking by exploiting one of its underlying properties: that different frequencies leak out of the slit at different angles.
"We input a wide range of terahertz frequencies into this waveguide in a single pulse, and each one leaks out simultaneously at a different angle," said Yasaman Ghasempour, a graduate student at Rice and co-author on the study. "You can think of it like a rainbow leaking out, with each color represents a unique spectral signature corresponding to an angle."
Now imagine a leaky waveguide placed on an access point. Depending upon where a client device is relative to the access point, it's going to see a different color coming out of the waveguide. The client just sends a signal back to the access point that says, "I saw yellow," and now the access point knows exactly where the client is, and can continue tracking it.
"It is not just about discovering the link once," Yasaman said. "In fact, the direction of transmission needs to be continually adjusted as the client moves. Our technique allows for ultra-fast adaptation which is the key to achieving seamless connectivity."
The setup also uses a leaky waveguide on the client side. On that side, the range of frequencies received through the slit in the waveguide can be used to determine the position of the router relative to the local rotation of the device -- like when someone swivels their chair while using a laptop.
Mittleman says that finding a novel way to make link discovery work in the terahertz realm is important because existing protocols for link discovery in microwaves simply won't work for terahertz signals. Even the protocols that have been developed for burgeoning 5G networks, which are much more directional than standard microwaves, aren't feasible for terahertz. That's because as narrow as 5G beams are, they're still around 10 times wider than the beams in a terahertz network.
"I think some people have assumed that since 5G is somewhat directional, this problem had been solved, but the 5G solution simply isn't scalable," Mittleman said. "A whole new idea is needed. This is one of those fundamental protocol pieces that you need to start building terahertz networks."
A new way to exploit the terahertz (THz) radio spectrum could prove cost-effective and reliable enough to commercialize new, under-used frequencies for high volume applications for 5G and beyond.
Developed at KTH Royal Institute of Technology, a new generation of methods and micro hardware is currently being used in a testbed by networks supplier Ericsson to run a fully-functional wireless link operating between 110-170 GHz at its Lindholmen lab facility in Sweden.
Lead author James Campion from the Department of Micro and Nanosystems at KTH, says the solution involves exploiting silicon to create affordable, scalable alternatives to existing hardware solutions. The authors reported their results recently in IEEE Transactions on Terahertz Science and Technology.
"We introduce the first integration of silicon-germanium active circuitry with silicon-micromachined waveguides," he says. "And for the first time, industrial-grade processes are being used to manufacture all system components, with automated assembly of the THz systems."
He says the integrated microelectromechanical actuators, which are possible in silicon-micromachined processes, enable the creation of low-cost tuneable systems in this approach. The micromachined waveguides are fabricated at KTH's Electrum Laboratory in Kista, with state-of-the-art integrated circuits designed by researchers at Ericsson and Chalmers fabricated at Infineon Technologies.
The recognition that THz frequencies are needed to support continued growth in data traffic around the world has led to a hunt for ways to enable the 100-500 GHz band for commercial use. In the U.S., the bands between 100-300 GHz have been allocated by the Federal Communications Commission for use in communications applications, providing a pathway for future commercialization.
Campion says that the solution overturns two major barriers to providing compact, low-cost point-to-point high-speed communication links in this frequency space. First is the cost of active circuitry, which is now based on fragile, thin substrates that can only be fabricated in small volumes; second, the metallic waveguides requiring precision on the order of tens of microns.
"This limits THz frequencies to one-off prototypes or scientific and research applications only," Campion says. These traditional systems also require precise manual assembly and cannot be produced in bulk, he says.
"The terahertz frequency spectrum must be used to support the continuous increases in global wireless data traffic," he says. "5G will not be sufficient—new solutions with higher bandwidth are required beyond 5G."
"Our approach can greatly reduce the cost of hardware and thereby enable widespread use of the THz spectrum, while the scalability allows for distributed applications for the internet-of-things and massive networks of miniaturized sensors."
While the wireless industry is firmly entrenched in deploying 5G networks—and in many cases, busy debunking myths surrounding it—plenty of academics and others are exploring what’s going to happen after 5G.
Test and measurement company Keysight Technologies, which has been there throughout the 5G standards process and even before that, recently announced that it has joined the multi-party 6G Flagship Program supported by the Academy of Finland and led by the University of Oulu, Finland.
Keysight actually has had a long relationship with Oulu University and has an R&D team based in Oulu, according to Roger Nichols, 5G program manager at Keysight, so it’s not as if this is coming out of the blue. According to a press release, however, Keysight is the only test and measurement provider thus far invited to take part in the program.
Keysight said its early research capability, complemented by a range of software and hardware for design, simulation and validation, will help the program accomplish its overarching goals. Those goals include supporting the industry in finalizing the adoption of 5G across verticals, developing fundamental technologies needed to enable 6G such as artificial intelligence (AI) and intelligent UX, and speeding digitalization of society.
The next generation of wireless communications is expected to leverage spectrum above millimeter waves. The terahertz waves, from 300 GHz to 3 THz, form an important component in delivering data rates of up to one terabit per second and ultra-low latencies, but they are still very much in the experimental territory.
“A lot of what’s happening up there now is still in the research phase because as you can imagine in those higher frequencies, it’s challenging to get things to work the way you want them,” Nichols told FierceWirelessTech. “We’ve been involved in that territory for quite a while,” having sub-100 GHz capability in its equipment for decades and using third-parties to extend that up into the terahertz range.
It’s not just about higher frequencies but what can be done with the wide bandwidths. For the sake of 6G, “really this is about: can we get an even wider bandwidth to deal with new applications that we haven’t thought about that have a demand for data rates that are well beyond anything we’re considering for 5G?” he said. “Obviously, going to terahertz super wide bandwidth is only part of 6G, just like millimeter wave is only part of 5G.”
Nichols points to an ITU Network 2030 white paper that describes the Network 2030 initiative and provides a comprehensive analysis of the applications, network, and infrastructure envisioned for the next big wireless transformation. That paper points to holographic type communications, multi-sense networks, time-engineered applications and critical infrastructure as emerging applications or use cases.
But nobody is suggesting it's a good idea to get ahead of themselves. Part of Keysight’s success in 5G was getting involved early and knowing where that technology was headed and the tools that are needed, plus developing relationships with academia and industry. “Clearly, we’re going to spend our time ensuring that we stay on top of that business opportunity, which is far from being over,” he said.
https://digital-library.theiet.org/content/books/cs/pbcs035e Communications technology at a frequency range into Terahertz (THz) levels has attracted attention because it promises near-fibre-optic-speed wireless links for the 5G and post-5G world. Transmitter and receiver integrated circuits based on CMOS, which has the ability to realize such circuits with low power consumption at a low cost, are expected to become increasingly widespread, with much research into the underlying electronics currently underway. This book describes recent research on terahertz CMOS design for high-speed wireless communication. The topics covered include fundamental technologies for terahertz CMOS design, amplifier design, physical design approaches, transceiver design, and future prospects. This concise source of key information, written by leading experts in the field, is intended for researchers and professional circuit designers working in RFIC and CMOS design for telecommunications.
UCLA Samueli School of Engineering’s Integrated Sensors Laboratory is collaborating with Airborne Wireless Network (ABWN), a leader in high-speed broadband aerial wireless networks, to field test its terahertz-band communication technology at medium altitude.
At present, the world’s wireless connectivity is achieved through undersea cables, ground-based fiber and satellites. A midair digital network is a potential solution to provide low cost, high-speed connectivity to commercial and private aircraft in flight, as well as remote areas such as island nations and territories, ships at sea, and oil platforms.
“We are excited to enter into this agreement and pair UCLA’s pioneering work in terahertz communications with our inventive work in air-to-air and air-to-ground mesh networks,” said Mike Warren, CEO of ABWN. “There are many areas of collaboration and mutual interest.”
The Integrated Sensors Laboratory, directed by Aydin Babakhani, associate professor of electrical and computer engineering, designs, fabricates, and tests silicon-based terahertz sensors and systems. The laboratory has reported the world’s first picosecond pulse generation and detection technology using silicon microchips and successfully demonstrated a long distance terahertz wireless communication link.
“We look forward to our collaboration with ABWN in deploying our terahertz technology on airborne platforms,” said Babakhani. “The large bandwidth and high directivity offered by our research is an ideal solution for establishing secure air-to-air wireless links. Terahertz also offers much larger bandwidth than today’s 5G systems. The technology has the potential to enable a link with over one terabits-per-second speed, which is fifty times higher than the peak data rate offered by today’s 5G systems.”
The UCLA-developed technology avoids the alignment and dispersion issues that limit the performance of free-space optical links. In addition to communication, the broadband terahertz pulse successfully augments the capabilities of precision radars and navigation systems, and also enables the identification and classification of small drones and other airborne objects through hyper-spectral sensing and micro-Doppler effects.
The technology will be tested at mid-level altitudes (10,000 to 15,000 feet) where it is expected to have inherent advantages over satellites; it will also be used to test and establish high bandwidth self-synchronizing airborne data links.
https://www.sciencedirect.com/science/article/pii/S0013935118300331 In the interaction of microwave radiation and human beings, the skin is traditionally considered as just an absorbing sponge stratum filled with water. In previous works, we showed that this view is flawed when we demonstrated that the coiled portion of the sweat duct in upper skin layer is regarded as a helical antenna in the sub-THz band. Experimentally we showed that the reflectance of the human skin in the sub-THz region depends on the intensity of perspiration, i.e. sweat duct's conductivity, and correlates with levels of human stress (physical, mental and emotional). Later on, we detected circular dichroism in the reflectance from the skin, a signature of the axial mode of a helical antenna. The full ramifications of what these findings represent in the human condition are still unclear. We also revealed correlation of electrocardiography (ECG) parameters to the sub-THz reflection coefficient of human skin. In a recent work, we developed a unique simulation tool of human skin, taking into account the skin multi-layer structure together with the helical segment of the sweat duct embedded in it. The presence of the sweat duct led to a high specific absorption rate (SAR) of the skin in extremely high frequency band. In this paper, we summarize the physical evidence for this phenomenon and consider its implication for the future exploitation of the electromagnetic spectrum by wireless communication. Starting from July 2016 the US Federal Communications Commission (FCC) has adopted new rules for wireless broadband operations above 24 GHz (5 G). This trend of exploitation is predicted to expand to higher frequencies in the sub-THz region. One must consider the implications of human immersion in the electromagnetic noise, caused by devices working at the very same frequencies as those, to which the sweat duct (as a helical antenna) is most attuned. We are raising a warning flag against the unrestricted use of sub-THz technologies for communication, before the possible consequences for public health are explore
The popularity, widespread use and increasing dependency on wireless technologies has spawned a telecommunications industrial revolution with increasing public exposure to broader and higher frequencies of the electromagnetic spectrum to transmit data through a variety of devices and infrastructure. On the horizon, a new generation of even shorter high frequency 5G wavelengths is being proposed to power the Internet of Things (IoT). The IoT promises us convenient and easy lifestyles with a massive 5G interconnected telecommunications network, however, the expansion of broadband with shorter wavelength radiofrequency radiation highlights the concern that health and safety issues remain unknown. Controversy continues with regards to harm from current 2G, 3G and 4G wireless technologies. 5G technologies are far less studied for human or environmental effects.
It is argued that the addition of this added high frequency 5G radiation to an already complex mix of lower frequencies, will contribute to a negative public health outcome both from both physical and mental health perspectives.
Radiofrequency radiation (RF) is increasingly being recognized as a new form of environmental pollution. Like other common toxic exposures, the effects of radiofrequency electromagnetic radiation (RF EMR) will be problematic if not impossible to sort out epidemiologically as there no longer remains an unexposed control group. This is especially important considering these effects are likely magnified by synergistic toxic exposures and other common health risk behaviors. Effects can also be non-linear. Because this is the first generation to have cradle-to-grave lifespan exposure to this level of man-made microwave (RF EMR) radiofrequencies, it will be years or decades before the true health consequences are known. Precaution in the roll out of this new technology is strongly indicated.
This article will review relevant electromagnetic frequencies, exposure standards and current scientific literature on the health implications of 2G, 3G, 4G exposure, including some of the available literature on 5G frequencies. The question of what constitutes a public health issue will be raised, as well as the need for a precautionary approach in advancing new wireless technologies.
New research shows that non-line-of-site terahertz data links are possible because the waves can bounce off of walls without losing too much data CREDIT Mittleman lab / Brown University
PROVIDENCE, R.I. [Brown University] -- An off-the-wall new study by Brown University researchers shows that terahertz frequency data links can bounce around a room without dropping too much data. The results are good news for the feasibility of future terahertz wireless data networks, which have the potential to carry many times more data than current networks.
Today's cellular networks and Wi-Fi systems rely on microwave radiation to carry data, but the demand for more and more bandwidth is quickly becoming more than microwaves can handle. That has researchers thinking about transmitting data on higher-frequency terahertz waves, which have as much as 100 times the data-carrying capacity of microwaves. But terahertz communication technology is in its infancy. There's much basic research to be done and plenty of challenges to overcome.
For example, it's been assumed that terahertz links would require a direct line of sight between transmitter and receiver. Unlike microwaves, terahertz waves are entirely blocked by most solid objects. And the assumption has been that it's not possible to bounce a terahertz beam around--say, off a wall or two--to find a clear path around an object.
"I think it's fair to say that most people in the terahertz field would tell you that there would be too much power loss on those bounces, and so non-line-of-sight links are not going to be feasible in terahertz," said Daniel Mittleman, a professor in Brown University's School of Engineering and senior author of the new research published in APL Photonics. "But our work indicates that the loss is actually quite tolerable in some cases -- quite a bit less than many people would have thought."
For the study, Mittleman and his colleagues bounced terahertz waves at four different frequencies off of a variety of objects--mirrors, metal doors, cinderblock walls and others -- and measured the bit-error-rate of the data on the wave after the bounces. They showed that acceptable bit-error-rates were achievable with modest increases in signal power.
"The concern had been that in order to make those bounces and not lose your data, you'd need more power than was feasible to generate," Mittleman said. "We show that you don't need as much power as you might think because the loss on the bounce is not as much as you'd think."
In one experiment, the researchers bounced a beam off two walls, enabling a successful link when transmitter and receiver were around a corner from each other, with no direct line-of-sight whatsoever. That's a promising finding to support the idea of terahertz local-area networks.
"You can imagine a wireless network," Mittleman explained, "where someone's computer is connected to a terahertz router and there's direct line-of-sight between the two, but then someone walks in between and blocks the beam. If you can't find an alternative path, that link will be shut down. What we show is that you might still be able to maintain the link by searching for a new path that could involve bouncing off a wall somewhere. There are technologies today that can do that kind of path-finding for lower frequencies and there's no reason they can't be developed for terahertz."
The researchers also performed several outdoor experiments on terahertz wireless links. An experimental license issued by the FCC makes Brown the only place in the country where outdoor research can be done legally at these frequencies. The work is important because scientists are just beginning to understand the details of how terahertz data links behave in the elements, Mittleman says.
Their study focused on what's known as specular reflection. When a signal is transmitted over long distances, the waves fan out forming an ever-widening cone. As a result of that fanning out, a portion the waves will bounce off of the ground before reaching the receiver. That reflected radiation can interfere with the main signal unless a decoder compensates for it. It's a well-understood phenomenon in microwave transmission. Mittleman and his colleagues wanted to characterize it in the terahertz range.
They showed that this kind of interference indeed occurs in terahertz waves, but occurs to a lesser degree over grass compared to concrete. That's likely because grass has lots of water, which tends to absorb terahertz waves. So over grass, the reflected beam is absorbed to a greater degree than concrete, leaving less of it to interfere with the main beam. That means that terahertz links over grass can be longer than those over concrete because there's less interference to deal with, Mittleman says.
But there's also an upside to that kind of interference with the ground.
"The specular reflection represents another possible path for your signal," Mittleman said. "You can imagine that if your line-of-site path is blocked, you could think about bouncing it off the ground to get there."
Mittleman says that these kinds of basic studies on the nature of terahertz data transmission are critical for understanding how to design the network architecture for future terahertz data systems.
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Mittleman's co-authors were Jianjun Ma, Rabi Shrestha and Lothar Moeller. The research was supported by the National Science Foundation and the W.M. Keck Foundation.
As the cellular networks continue to progress between generations, the expectations of 5G systems are planned toward high-capacity communication links that can provide users access to numerous types of applications (e.g., augmented reality and holographic multimedia streaming). The demand for higher bandwidth has led the research community to investigate unexplored frequency spectrums, such as the terahertz band for 5G. However, this particular spectrum is strived with numerous challenges, which includes the need for line-of-sight (LoS) links as reflections will deflect the waves as well as molecular absorption that can affect the signal strength. This is further amplified when a high quality of service has to be maintained over infrastructure that supports mobility, as users (or groups of users) migrate between locations, requiring frequent handover for roaming. In this paper, the concept of mirror-assisted wireless coverage is introduced, where smart antennas are utilized with dielectric mirrors that act as reflectors for the terahertz waves. The objective is to utilize information such as the user's location and to direct the reflective beam toward the highest concentration of users. A multiray model is presented in order to develop the propagation models for both indoor and outdoor scenarios in order to validate the proposed use of the reflectors. An office and a pedestrian-walking scenarios are used for indoor and outdoor scenarios, respectively. The results from the simulation work show an improvement with the usage of mirror-assisted wireless coverage, improving the overall capacity, the received power, the path loss, and the probability of LoS.
Imagine downloading a movie to your smartphone in less than a second. That’s the potential of the next generation (5G) of cellular network technology. Researchers say it will allow wireless transfer of data 10 times faster than the current 4G network. It will also have more capacity and better reach with multiple improved smaller antennas.
“The fifth generation (5G) cellular networks are coming,” explains Payam Heydari, a UC Irvine electrical engineering professor whose expertise is in the design and analysis of novel terahertz, millimeter-wave and radio-frequency integrated circuits, technologies that could revolutionize power-efficient wireless sensor networks.
As an IEEE Distinguished Lecturer for the Solid-State Circuits Society, Heydari spoke about the challenges and solutions of developing 5G technologies with engineering students and faculty at three East Coast universities: Lehigh, Princeton and Columbia.
“Millimeter-wave (mm-wave) and terahertz (THz) bands are underutilized regions of the electromagnetic spectrum that have generated a great deal of excitement for future systems that would be able to achieve very high speed wireless data transfer as well as wideband sensing/imaging applications,” Heydari explains. “The shorter wavelength associated with these bands is appealing since the physical dimensions of the antenna and associated electronics can be smaller, making it possible to design multiple antenna structures that can emit signals in various directions and even bounce off buildings.”
On the lecture tour, Heydari presented an overview of recent advances in designing silicon-based integrated circuits. He discussed two case studies from UCI’s Nanoscale Communication Integrated Circuits Labs. One is the first 210-gigahertz wireless transceiver in complementary metal–oxide–semiconductor technologies that enables 20 gigabit-per-second wireless data transfer, and the second is the world’s highest frequency synthesizer at 300 gigahertz with a wide –tuning range, allowing very high resolution radar sensors for surveillance and security systems.
This is a crucial time in the development of 5G. “We are talking about what technologies will define this next generation,” says Heydari. “Will 5G be just an evolution of 4G, or will emerging technologies cause a disruption requiring a wholesale rethinking of entrenched cellular principles?”
IEEE Distinguished Lecturers are engineering professionals who lead their fields in new technical developments that shape the global community. They serve two-year terms and deliver lectures at chapter meetings and regional seminars around the world.
It is that time of the year again when Swami Hindle makes his Microwave Industry Predictions. Last year, some of the hot industry topics included GaN PAs, focus on PA efficiency (envelope tracking, outphasing techniques, etc.), the start of CMOS PA adoption, software defined test instrumentation (and adoption of the PXI platform), tunable device technology for antennas, 4G technologies such as MIMO/carrier aggregation. Here are my predictions for 2014:
5G systems will be proto-typed and tested (massive MIMO, millimeter/terahertz, etc.)
Heterogeneous networks will start to relieve the capacity crunch
Metamaterials will step out of the lab into mainstream applications
60 GHz applications will take off as the cost of those modules plunges
Connected vehicles and homes will start to be realized in mass
CMOS (mostly SOI) will gain market significant RF market share
Modeling and simulation software will see major integration with test equipment
Low cost T&M instrument companies will thrive but many will be consolidated into the larger companies
3D packaging will take off in commercial markets
New heat sinking technologies will be developed to greatly improve GaN amplifier efficiency/reliability
UAV technology will see huge growth in the commercial markets and software/sensors will be developed to let them make their own decisions without an operators intervention
The current T/R module approach to AESA radars will be replaced by another architecture that greatly reduces SWaP-C
What predictions do you have for 2014? Let us know by commenting here.
Pat Hindle, MWJ Technical Editor
Pat Hindle is responsible for editorial content, article review and special industry reporting for Microwave Journal magazine and its web site in addition to social media and special digital projects. Prior to joining the Journal, Mr. Hindle held various technical and marketing positions throughout New England, including Marketing Communications Manager at M/A-COM (Tyco Electronics), Product/QA Manager at Alpha Industries (Skyworks), Program Manager at Raytheon and Project Manager/Quality Engineer at MIT. Mr. Hindle graduated from Northeastern University - Graduate School of Business Administration and holds a BS degree from Cornell University in Materials Science Engineering.
[SatNews] A line of frequency-extension modules from Virginia Diodes Inc. (VDI), a company that designs, manufactures and sells millimeter-wave and terahertz devices, components and systems, for its signal generators and analyzers, has debuted by Agilent Technologies Inc. (NYSE: A). http://www.satnews.com/story.php?number=1608451500
Covering millimeter frequencies up to 1.1THz, the VDI modules extend the reach of Agilent’s signal generators and analyzers to address growing needs in early next-generation wireless research, sometimes referred to as 5G. The VDI modules are also ideal for working with millimeter-wave communication backhaul systems and emerging wireless standards such as IEEE 802.11ad, as well as a range of aerospace/defense applications.
High frequency measurements up to 1.1 THz are easier than ever with new frequency extension modules from VDI for the Agilent PXA/EXA signal analyzers (N9029AVxx) and the PSG signal generator (E8257DVxx).
As applications move to higher frequencies to support increased modulation bandwidth and seek out an uncrowded spectrum, measurement challenges increase dramatically. Agilent’s signal generators and analyzers, coupled with the new extender modules from VDI, address these challenges by enabling designers to accurately generate and analyze complex millimeter-wave signals.
P> The new VDI modules offer much higher performance than other frequency extenders, enabling better measurement results. The VDI source modules, for example, offer higher output power, while the VDI signal analyzer modules reduce conversion loss and increase sensitivity. Performance specifications such as these provide greater overall dynamic range for a variety of measurements.
The VDI signal analyzer modules offer two modes of operation: standard external mixer and wideband block downconverter. The block downconverter mode enables analysis of wideband modulated signals using either an Agilent signal analyzer or wideband digital oscilloscope running Agilent 89600 VSA software.
Clothes, cars, trains, tractors, body sensors, and tracking tags. By the end of this decade, analysts say, 50 billion things such as these will connect to mobile networks. They’ll consume 1000 times as much data as today’s mobile gadgets, at rates 10 to 100 times as fast as existing networks can support. So as carriers rush to roll out 4G equipment, engineers are already beginning to define a fifth generation of wireless standards.
What will these “5G” technologies look like? It’s too early to know for sure, but engineers at Samsung and at New York University say they’re onto a promising solution. The South Korea–based electronics giant generated some buzz when it announced a new 5G beam-forming antenna that could send and receive mobile data faster than 1 gigabit per second over distances as great as 2 kilometers. Although the 5G label is premature, the technology could help pave the road to more-advanced mobile applications and faster data transfers.
Samsung’s technology is appealing because it’s designed to operate at or near “millimeter-wave” frequencies (3 to 300 gigahertz). Cellular networks have always occupied bands lower on the spectrum, where carrier waves tens of centimeters long (hundreds of megahertz) pass easily around obstacles and through the air. But this coveted spectrum is heavily used, making it difficult for operators to acquire more of it. Meanwhile, 4G networks have just about reached the theoretical limit on how many bits they can squeeze into a given amount of spectrum.
So some engineers have begun looking toward higher frequencies, where radio use is lighter. Engineers at Samsung estimate that government regulators could free as much as 100 GHz of millimeter-wave spectrum for mobile communications—about 200 times what mobile networks use today. This glut of spectrum would allow for larger bandwidth channels and greater data speeds.
Wireless products that use millimeter waves already exist for fixed, line-of-sight transmissions. And a new indoor wireless standard known as WiGig will soon allow multigigabit data transfers between devices in the same room. But there are reasons engineers have long avoided millimeter waves for broader mobile coverage.
Illustration: Erik Vrielink5g Beam Scheme: Steerable millimeter-wave beams could enable multigigabit mobile connections. Phones at the edge of a 4G cell [blue] could use the beams to route signals around obstacles. Because the beams wouldn’t overlap, phones could use the same frequencies [pink] without interference. Phones near the 4G tower could connect directly to it [green].
For one thing, these waves don’t penetrate solid materials very well. They also tend to lose more energy than do lower frequencies over long distances, because they are readily absorbed or scattered by gases, rain, and foliage. And because a single millimeter-wave antenna has a small aperture, it needs more power to send and receive data than is practical for cellular systems.
Samsung’s engineers say their technology can overcome these challenges by using an array of multiple antennas to concentrate radio energy in a narrow, directional beam, thereby increasing gain without upping transmission power. Such beam-forming arrays, long used for radar and space communications, are now being used in more diverse ways. The Intellectual Ventures spin-off Kymeta, for instance, is developing metamaterials-based arrays in an effort to bring high-speed satellite broadband to remote or mobile locations such as airplanes.
Samsung’s current prototype is a matchbook-size array of 64 antenna elements connected to custom-built signal-processing components. By dynamically varying the signal phase at each antenna, this transceiver generates a beam just 10 degrees wide that it can switch rapidly in any direction, as if it were a hyperactive searchlight. To connect with one another, a base station and mobile radio would continually sweep their beams to search for the strongest connection, getting around obstructions by taking advantage of reflections.
“The transmitter and receiver work together to find the best beam path,” says Farooq Khan, who heads Samsung’s R&D center in Dallas. Khan and his colleagues Zhouyue Pi and Jianzhong Zhang filed the first patent describing a millimeter-wave mobile broadband system in 2010. Although the prototype revealed this year is designed to work at 28 GHz, the Samsung engineers say their approach could be applied to most frequencies between about 3 and 300 GHz. “Our technology is not limited to 28 GHz,” Pi says. “In the end, where it can be deployed depends on spectrum availability.”
In outdoor experiments near Samsung’s Advanced Communications Lab, in Suwon, South Korea, a prototype transmitter was able to send data at more than 1 Gb/s to two receivers moving up to 8 kilometers per hour—about the speed of a fast jog. Using transmission power “no higher than currently used in 4G base stations,” the devices were able to connect up to 2 km away when in sight of one another, says Wonil Roh, who heads the Suwon lab. For non-line-of-sight connections, the range shrank to about 200 to 300 meters. Theodore Rappaport, a wireless expert at the Polytechnic Institute of NYU, has achieved similar results for crowded urban spaces in New York City and Austin, Texas. His NYU Wireless lab, which has received funding from Samsung, is working to characterize the physical properties of millimeterwave channels. In recent experiments, he and his students simulated beam-forming arrays using megaphone-like “horn” antennas to steer signals. After measuring path losses between two horn transceivers placed in various configurations, they concluded that a base station operating at 28 or 38 GHz could provide consistent signal coverage up to about 200 meters.
Millimeter-wave transceivers may not make useful replacements for current cellular base stations, which cover up to about a kilometer. But in the future, many base stations will likely be much smaller than today’s, Rappaport points out. Already carriers are deploying compact base stations, known as small cells, in congested urban areas to expand data capacity. Not only could millimeter-wave technology add to that capacity, he says, it could also provide a simple, inexpensive alternative to backhaul cables, which link mobile base stations to operators’ core networks.
“The beauty of millimeter waves is there’s so much spectrum, we can now contemplate systems that use spectrum not only to connect base stations to mobile devices but also to link base stations to other base stations or back to the switch,” Rappaport says. “We can imagine a whole new cellular architecture.”
Other wireless experts remain skeptical that millimeter waves can be widely used for mobile broadband. “This is still theoretical; it has to be proven,” says Afif Osseiran, a master researcher at Ericsson and project coordinator for the Mobile and wireless communication Enablers for the Twenty-twenty Information Society (METIS). The newly formed consortium of European companies and universities is working to identify the most promising 5G solutions by early 2015.
Osseiran says METIS is considering a variety of technologies, including new data coding and modulation techniques, better interference management, densely layered small cells, multihop networks, and advanced receiver designs. He emphasizes that a key characteristic of 5G networks will be the use of many diverse systems that must work together. “Millimeter-wave technology is only one part of a bigger pie,” he says. This article originally appeared in print as “The 5G Phone Future.”
Imagine downloading a movie to your smartphone in less than a second. That’s the potential of the next generation (5G) of cellular network technology. Researchers say it will allow wireless transfer of data 10 times faster than the current 4G network. It will also have more capacity and better reach with multiple improved smaller antennas.
On the lecture tour, Heydari presented an overview of recent advances in designing silicon-based integrated circuits. He discussed two case studies from UCI’s 
5G systems will be proto-typed and tested (massive MIMO, millimeter/terahertz, etc.)
