Antennas are our electronic eyes and ears on the world. They play a very important role in mobile networks, satellite communications system, military communications, radars and electronic warfare by transforming a Radiofrequency ( RF) signal, traveling on a conductor, into an electromagnetic wave in free space and vice versa. The RF current flowing through the antenna produce electromagnetic waves which radiate into the atmosphere.
The first radio antennas were built by Heinrich Hertz, a professor at the Technical institute in Karlsruhe, Germany. Since then many varieties of antennas have proliferated including dipoles/monopoles, loop antennas, slot/horn antennas, reflector antennas, microstrip antennas, log periodic antennas, helical antennas, dielectric/lens antennas and frequency-independent antennas have been . Each category possesses inherent benefits that make them more or less suitable for particular applications.
Antennas for cellular phones and all types of wireless devices link us to everyone and everything.The main objective in designing antenna system for mobile devices is that that can operate for all existing band of mobile phone from 2G to 4G, and also for extension band planned for 5G communications.
The shrinking of mobiles is demanding miniaturization of the antenna as much as possible while preserving the efficiency. The numerous advantages of planar or microstrip antenna, such as its low weight, small volume, and ease of fabrication using printed circuit technology, led to the design of several configurations for various personal and mobile applications.
The miniaturization is also needed because it will enable to integrate multiple antennas in a device to support MIMO schemes. Multiple transmit and multiple receive (MIMO) antennas has emerged as one of the most significant technical breakthroughs in next generation wireless communications. MIMO is the use of multiple antennas at both the transmitter and receiver to improve communication performance.
Wearable applications require antennas and electronic devices to be embedded into clothing. Generally they need to be small, lightweight, conformal, and reliable. A widely studied approach to meet these requirements is fabrication of antennas from electrically conductive textiles (e-textiles).
Antenna Requirements in 5G , IoT and military
5G cellular networks promise to improve many aspects of wireless communications, supporting enhanced mobile services, greater scalability for IoT systems, and ultra-reliable communications for mission-critical applications.
5G requires advanced antenna technologies that allow handsets to have both sub-6 GHz and mmWave antenna systems coexisting in the same device while achieving strict performance requirements.. Advanced materials can be combined with smart antenna and MIMO technologies to create flexibly performing antennas with ultra-wide bandwidth and high efficiencies.
The antenna are required in military for land-based, naval, and airborne communications, as well as communications intelligence (COM- INT) and electronic warfare (EW) systems including communications electronic support measures (CESM) and communications electronic countermeasures (CECM). The aperture size is constrained by the dimensions of the host platform (e.g. aircraft or naval ship).
Antenna requirements for military applications include low profile, high efficiency, wide frequency band, highly integrated and conformability to the host platform. The low profile and conformality stem from the desire to blend the antenna into its surroundings to avoid easy visible detection and identification. These applications often require novel antenna solutions.
Military Antennas encompasses a wide range of highly sensitive active and passive, omnidirectional and directional, and broadband antennas for mobile and stationary use, covering wide spectrum from the 100 Hz to 40 GHz frequency range. Wideband antennas are essential for military systems requiring spectrum-agility or multi-functionality.
Military and aerospace users are keenly interested in developing antennas for SATCOM-on-the-move (SOTM) technology for land, sea, and airborne applications. “Going forward, the parabolic- designed antenna will continue to be the mainstay for SOTM terminals because of its efficiency,” Marvin Shoemake, vice president of business development, General Dynamics SATCOM Technologies in Duluth, Ga. predicts.
The development of ultra-compact antennas has great significance to military as it leads to miniaturisation of military and commercial communication systems.. The miniaturization of military electronics is of significant benefit to the warfighter, not only in terms of device size, but in transportability, space requirements, weight, and many factors,” said Howe. “It can allow us to fit more into a given space, whether that be in a field pack or on an aerial platform. It gives us greater capability in a smaller space.
Military applications combine the need for high performance and reliability with some of the hardest environmental conditions, explains Klaus Fischer, product manager, Antennas, Rhode & Schwarz in Munich, Germany. “This especially applies to antenna products, as they are generally the most exposed equipment of any system.
The need for supporting extremely high data transfer rate capable military communication systems in diverse communication environments is also driving the development of novel compact antennas and arrays. Experts predict that antennas of tomorrow will likely be smaller than today yet provide superior performance, and metamaterial technology will play an important role in new antenna development.
Modern antenna systems in mobile devices and transmission towers are increasingly being set up as arrays of antenna elements to increase performance, directionality, bandwidth and safety. For example, by adjusting the phase of individual antenna elements, the radiation pattern from an antenna array in a mobile phone can be directed away from the user for safety, while the radiation pattern from a transmission tower can be concentrated on a specific area for improved coverage. There is a demand for high-performance antenna array systems in numerous applications, such as radar surveillance, biomedical imaging, remote sensing, radio astronomy and satellite communications.
The goal of DARPA Arrays at Commercial Timescales (ACT) program is to develop a common technology base for Electronically Scanned Array (ESA) systems. Historically, most fielded ESA systems have been comprised of highly tailored, application-specific layers.
Bluewater Defense, Inc. and Vorbeck Materials Corp. have introduced of next generation, high performance wearable antennas for military, tactical and commercial use in apparel and equipment featuring multiple communication bands including LTE capabilities at AUSA 2016. They offered robust, high-gain, low-cost, and discrete conformal printed graphene antennas embedded in military apparel and backpacks. Benefits include: Increase existing cell phone coverage by up to 200%, Significant improvements of upload and download speeds, Omni-directional coverage through the deployment of an array of antennas, Supports wide frequency range from 800-3000 Mhz, Durable, flexible, washable and non-corrosive — environmentally friendly and Increased battery life by reducing operating power.
Cellular Wireless Antennas
Due to the migration to 4G cellular networks, additional frequency bands are used by network providers to increase service level speeds and throughput. Many IoT devices require that antennas be able to send and receive efficiently at all bands to be globally compliant, without the need to change antennas based on region. Devices may also require 2G/3G fallback. Traditionally this is achieved by increasing the ground-plane length of the board the antenna is mounted on. As a result, many devices are larger than is required—or practical—for the application they serve. Taoglas unveils what it calls a revolutionary breakthrough in antenna design that will deliver significantly increased antenna performance. This innovation is particularly suited to designs with shorter ground planes.
Taoglas Boost handles the challenge with a new technique to alter the electrical delay in the ground plane to improve efficiency at the lower frequencies (600 to 1,000 MHz) typically used for cellular applications. The modification can be implemented in the “keep-out” area of the antenna, the area on the host circuit board reserved for antenna placement, causing minimal impact to the designer in terms of antenna integration.
A tuning feature is integrated into the design to allow for quick optimization as Taoglas Boost is implemented in a user device. The result is up to 2 dB of antenna efficiency improvement on the same ground plane length compared to traditional technology. Extra antenna gain improves any system-level gain, but this improvement can be particularly useful to meeting over-the-air (OTA) requirements for size-constrained devices commonly found in M2M and IoT applications.
Active steering Antennas
Ethertronics has unveiled a new chip that will bring its active steering algorithms to Wi-Fi antennas, increasing their range and boosting their throughput in less than optimal conditions. Active steering essentially creates multiple radiation patterns around the same antenna and then selects the ideal pattern to hit its targeted device with best signal. Ethertronics has demonstrated in its tests, a 20 percent to 45 percent increase in throughput between access points and devices living on the fringes of a network.
Wyler claims breakthrough in low-cost antenna for OneWeb, other satellite systems
OneWeb founder Greg Wyler says a self-funded side project of his has developed an antenna module costing $15, paving the way for user terminals priced between $200 and $300. Wyler described the antenna as the “critical and hardest subcomponent” of the terminal.
Antenna is of electronically scanned antenna array type that would work with OneWeb satellites and other constellations. Constellations in low and medium Earth orbits, unlike geostationary satellites, move across the sky. Keeping in contact with such satellites requires ground terminals capable of tracking the satellites, either by mechanically repositioning a dish or using a stationary antenna that uses so-called electronic steering, or scanning, to maintain the connection.
“The entire antenna is less than an eighth inch thick,” he said. “So the breakthrough is that you can have an extremely light, thin, low-power antenna that’s very cost effective and can be produced in large volumes.”
Satixfy prepares release of flat panel antennas this year
British and Israeli satellite antenna developer Satixfy says it is nearing the release of flat-panel products designed first for connecting internet of things devices, with variants for other markets following shortly.Rajanik Mark, Satixfy’s chief operating officer, said the company has created its own chipsets that it can build in-house to bring down the cost of antenna modules for implementation in full user terminals.
Satixfy is one of around two dozen companies working on flat panel antennas capable of connecting with two or more satellites simultaneously — a feature widely viewed as critical for proposed large constellations of broadband satellites that would orbit too fast for most if not all dish antennas.
Satixfy terminals will use electronic steering instead of mechanical systems to track satellites. Mark said a Satixfy terminal can connect to as many as 32 satellites at once. “You don’t have a case of make-before-break,” he said, describing a situation unique to non-geosynchronous satellites where an antenna needs to switch links from one spacecraft to another as they rise and set over the horizon. “You would have the signal on all the time. And you could have situations where you may not have [low Earth orbit] coverage … we could in that situation talk to a LEO as well as a GEO simultaneously if they are operating in the same frequency band.”
Mark said Satixfy plans to release a Ku-band terminal based on that antenna this fall optimized for connecting sensors and other internet of things devices, followed by an aeronautical terminal in 2020.
Massive MIMO Antennas for 5G
Multiple Input Multiple Output (MIMO) techniques are one of key technologies in 5G systems. The main idea is to use the multiple antennas at a transmitter and receiver to improve the performance of wireless communication systems. Namely, a higher number of MIMO antennas mean a higher spectral efficiency. Massive (or Very Large) MIMO techniques use more than 100 antennas. A massive MIMO technique can increase 10 times or more channel capacity and improve 100 times or more energy efficiency. MIMO technique is well matched at a high frequency technique such as millimeter wave (mmWAVE) techniques.
Samsung Electronics, has announced the development of breakthrough 5G-ready case-integrated antenna, which incorporates dozens of antenna elements in a module that is less than 1mm thick – a critical step towards engineering both compact small cell base stations and user devices. The new technologies are intended to be applied to both 5G base stations and end-user devices using 28GHz millimeter wave (mmWave) spectrum. mmWave frequencies are widely expected to be one of the primary enablers of next-generation networks.
Size is particularly critical for 5G devices, as the peak and average throughputs of next-generation networks are expected to be on the gigabit-scale, where radio signal processing and power consumption can be very high without appropriately efficient technologies. Also, due to the naturally short range of the high frequency mmWave spectrum, network coverage strategies will likely require dense deployments of 5G small cells mounted in inconspicuous locations on walls and utility poles. These small cells thus need to be as small, light and efficient as possible.
Smart Antennas use a few key technologies to improve 5G capacity and coverage. One such technology is beamforming in which RF energy is focused in a narrow beam to exactly where it is needed rather than emanating the same energy in a broad area. Beamforming is especially useful for 5GNR as the higher frequency mmWave RF is subject to fading over distance and attenuation loss caused by hitting objects (buildings, cars, foliage, etc.). A more directed beam of RF energy helps to ensure a greater probability of optimal bandwidth and signal quality.
5G systems will also need Smart Antennas to optimize coverage, mobility, and minimize the need for hand-over from 5G to 4G RAN. Smart Antennas are useful to optimize LTE, but they are absolutely necessary to provide mobility support for many new and enhanced 5G apps and services such as virtual reality, self-driving cars, connected vehicles, and Voice over 5G (Vo5G).
Smart Antennas for 5G will improve coverage and optimize capacity by focusing RF signals where they are needed the most. In addition, Smart Antennas enhance 5G application and service mobility by facilitating a more continuous connection, which may become particularly useful at 5G coverage seams
Researchers at Utah State University are developing smarter antenna to improve cell phone service and data streaming that can dynamically change its properties like frequency, polarization, and radiation pattern. A circuit board allows the antenna to morph its dimensions to better function with the varying signals. The goal of the research is to be able to maintain optimum performance at all times on all wireless devices. U.S. Air Force recently gave USU a grant for $1 million to expand the research.
Adaptive antenna systems can steer the main beam in a desired direction and spatial nulls in undesired directions to avoid interference. Adaptive antenna systems represent a significant element of design for enhanced small‐cell deployment. These kinds of adaptive antenna systems can enable extension of transmission range, increase of data throughput, enhance spectrum reuse, and substantially reduce co-channel interference which is one critical issue in future heterogeneous wireless communications systems where classical macro networks and more advanced small cell systems are coexisting.
Tiny Membrane-Based Antennas
The new antennas developed by researchers at Northeastern University and their collaborators can now be shrunk to sizes as small as one-thousandth of the wavelength they aim to receive and transmit—without any degradation in performance. The researchers detailed their findings online today in the journal Nature Communications. These antennas could find use in portable wireless communications systems, including wearable electronics, smartphones, bio-implantable antennas, bio-injectable antennas, bio-ingestible antennas, and the Internet of Things, researchers say.
These new antennas consist of thin membranes made up of two different kinds of films. Its piezomagnetic iron-gallium-boron layers convert mechanical oscillations to magnetic signals and vice versa. They are paired with piezoelectric aluminum nitride films, which convert mechanical oscillations to electrical signals and vice versa. When these membranes receive electromagnetic signals, their magnetic layers sense the magnetic fields of these electromagnetic waves. This causes the membranes to vibrate, which piezoelectrically generates a voltage. Conversely, in order for the antennas to transmit, they vibrate. This causes the magnetic layers of the membranes to generate a magnetic current that radiates electromagnetic waves.
BAE Systems Gets US Army Contract for developing Advanced Radar Jamming Technology
BAE Systems was awarded research and development funding through the U.S. Army to create an advanced radar jamming technology. The technology aims to improve air survivability and mission effectiveness for U.S. Army rotary-wing aircraft and unmanned aerial systems (UAS) by detecting and defeating complex and unknown threats in electronic combat.
As part of the contract, BAE Systems FAST Labs R&D team will design technology to integrate adaptive radio frequency jamming and sensing capabilities into one system. Whereas today’s electronic countermeasure systems are too bulky and heavy for most rotary-wing and UAS platforms, BAE Systems technology will combine multiple, software-programmable antennas into a digital phased array that will enable simultaneous functions, exceeding existing capabilities while reducing the size, weight, and power (SWaP) of current systems. The technology will enable these platforms to safely fly closer to threats and within contested areas while remaining protected.
UT Austin Engineers Design Next-Generation Non-Reciprocal Antenna
Andrea Alù, associate professor in the Department of Electrical and Computer Engineering, along with postdoctoral fellows Yakir Hadad and Jason Soric, have designed a non-reciprocal antenna, as reported in the Proceedings of the National Academy of Sciences.“Our achievement is that we break the symmetry between transmission and reception signals, so we are able to prevent the antenna from having to listen to reflections and echoes that affect the source,” Alù said.
“We show that it is possible to efficiently overcome these constraints using temporally modulated traveling-wave antennas.” This enables faster data rates and improved connections while requiring less bulky antenna systems.Beyond telecommunications, the new antenna technology may be applied to sensors used in applications as diverse as health care and weather tracking, allowing the sensors to pick up stronger signals for more accurate data collection.
Conventional antennas are subject to reciprocity, or the natural symmetry in radiation characteristics while transmission or reception, because of which they unavoidably transmit and receive signals with the same efficiency. As it happens, this property is not always a beneficial feature because transmitting antennas are prone to absorb surrounding reflections or echoes that bounce back from nearby obstacles. This noise deteriorates the quality of the transmission signals.
In the team’s experiments, the researchers fed the antenna with two signals simultaneously: the radio-frequency signal that they want to transmit or receive, and a weak low-frequency modulation signal that slowly changes the properties of the antenna as the radio-frequency signal travels along it. This modulation breaks the inherent symmetry of the antenna in transmission and reception, overcoming the reciprocity constraints. Presently in the telecommunications field, magnet-based isolators are commonly used as part of antenna systems to prevent received signals from traveling into the transmission amplifier. The researchers believe their new antenna may be an efficient solution to significantly reduce the need of isolators and reduce the size and cost of telecommunication systems.
AFRL developing ultra compact Antennas
The US Air Force Research Laboratory (AFRL) has disclosed details of research into a new generation of ultra-compact antennas that could mark a breakthrough in the miniaturisation of military and commercial communication systems. Researchers at the AFRL Materials and Manufacturing Directorate, in partnership with Northeastern University, have exploited new material technologies to reduce the size of an antenna by more than 90%.
These ultra-compact antennas represent a whole different approach to this type of technology. Instead of using an electrically-conductive material to sense the electric field of microwaves, these antennas use special insulating materials, called “multiferroic composites.” These materials are composed of magnetostrictive materials, which convert magnetism to strain, and piezoelectric materials, which convert strain to voltage converting material. Using the multiferroic composites allows the ultra-compact antennas to function by sensing the magnetic field of microwaves.
“We miniaturized the antennas by borrowing a trick from acoustic filters in cellphones, which convert microwave voltages to strain waves. Strain waves travel much slower than the speed of light, so by doing this, we are able to shrink the wavelengths while keeping the frequency the same. This allowed us to make the antennas much smaller,” said AFRL materials scientist Dr. Michael McConney. He added that by coating conventional bulk acoustic wave filters with a magnetic material, these slower strain waves can be converted into radiation, which enabled them to break the inefficient scaling laws associated with shrinking typical antennas to very small sizes.
In a paper published online in Nature Communications, Nian Sun, professor of electrical and computer engineering at Northeastern, and his colleagues describe a new approach to designing antennas. The discovery enables researchers to construct antennas that are up to one hundred times smaller than currently available antennas, Sun said.
Traditional antennas are built to receive and transmit electromagnetic waves, which travel fast—up to the speed of light. But electromagnetic waves have a relatively long wavelength. That means antennas must maintain a certain size in order to work efficiently with electromagnetic radiation.
Instead of designing antennas at the electromagnetic wave resonance—so they receive and transmit electromagnetic waves—researchers tailored the antennas to acoustic resonance. Acoustic resonance waves are roughly 10 thousand times—smaller than electromagnetic waves. This translates to an antenna that’s one or two orders of magnitude smaller than even the most compact antennas available today.
Since acoustic resonance and electromagnetic waves have the same frequency, the new antennas would still work for cell phones and other wireless communication devices. And they would provide the same instantaneous delivery of information. In fact, researchers found their antennas performed better than traditional kinds. Tiny antennas have big implications, especially for Internet of Things devices, and in the biomedical field. For example, Sun said the technology could lead to better bioinjectible, bioimplantable, or even bioinjestible devices that monitor health.
One such application that neurosurgeons are interested in exploring is a device that could sense neuron behavior deep in the brain. But bringing this idea to life has stumped researchers, until now. “Something that’s millimeters or even micrometers in size would make biomedical implantation much easier to achieve, and the tissue damage would be much less,” Sun said.
Inflatable satellite antennas
US and coalition forces are using lightweight, easily transportable Ground Antenna Transmit & Receive or GATR Inflatable satellite antennas, enabling them to achieve high-bandwidth network connectivity anywhere in the world from small deployable packages. Fitting in just two transit cases, the GATR antenna provides the same robust data links as conventional rigid satellite dishes, but weighs up to 80 percent less. The spherical shape greatly reduces the effect of wind, and a unique cable anchoring system assures stability in winds exceeding 40 mph, and survivability up to 60 mph–wind speeds that can interrupt connectivity in all other terminals.
Distributed Aperture satellite Antenna
US Army is poised for a breakthrough in Antenna that would make command armored vehicles less detectable to enemies and safer to operate. The current SATCOM dish antennas are too bulky and cumbersome to fit inside heavy vehicles like the Bradley or the Abrams tank that have turreted weapon systems. The Army’s communications technology lab has identified distributed aperture terminals technology, wherein small antennas can be inserted on the exterior of the vehicle, to help shrink SATCOM systems. The Army Communications Electronics Research & Development Engineering Center (CERDEC) has awarded Harris Corp. a 29-month, $10 million fixed-price contract to build a distributed aperture satellite communications system in a Bradley infantry personnel carrier.
Low profile antennas
DARPA has awarded Kerby-Patel applied electromagnetics researcher the 2015 Young Faculty Award (YFA) for research into flatter low profile antennas that can be employed on both manned and unmanned aerial vehicles for navigation and communications. “I’m working on a new way to design low-profile antennas backed by high impedance surfaces,” says Kerby-Patel. “High impedance surfaces are a promising new material for antennas, but right now there is a lot of trial and error in the design process. We’re trying to eliminate that trial and error.”
Her research involves three components: First, she will develop a model that simplifies the physics of the antenna into an equivalent circuit. Second, she’ll compare the behavior of the actual antenna to the model using electromagnetic simulation software and real-world experiments. Finally, she’ll use the new physical detail captured by the model to create novel methods for designing low-profile antennas.
Merging Antenna and Electronics Boosts Energy and Spectrum Efficiency
By integrating the design of antenna and electronics, researchers have boosted the energy and spectrum efficiency for a new class of millimeter wave transmitters, allowing improved modulation and reduced generation of waste heat. The result could be longer talk time and higher data rates in millimeter wave wireless communication devices for future 5G applications.
“In this proof-of-example, our electronics and antenna were designed so that they can work together to achieve a unique on-antenna outphasing active load modulation capability that significantly enhances the efficiency of the entire transmitter,” said Hua Wang, an assistant professor in Georgia Tech’s School of Electrical and Computer Engineering. “This system could replace many types of transmitters in wireless mobile devices, base stations and infrastructure links in data centers.”
Key to the new design is maintaining a high-energy efficiency regardless whether the device is operating at its peak or average output power. The efficiency of most conventional transmitters is high only at the peak power but drops substantially at low power levels, resulting in low efficiency when amplifying complex spectrally efficient modulations. Moreover, conventional transmitters often add the outputs from multiple electronics using lossy power combiner circuits, exacerbating the efficiency degradation.
“We are combining the output power though a dual-feed loop antenna, and by doing so with our innovation in the antenna and electronics, we can substantially improve the energy efficiency,” said Wang, who is the Demetrius T. Paris Professor in the School of Electrical and Computer Engineering. “The innovation in this particular design is to merge the antenna and electronics to achieve the so-called outphasing operation that dynamically modulates and optimizes the output voltages and currents of power transistors, so that the millimeter wave transmitter maintains a high energy efficiency both at the peak and average power.”
Beyond energy efficiency, the co-design also facilitates spectrum efficiency by allowing more complex modulation protocols. That will enable transmission of a higher data rate within the fixed spectrum allocation that poses a significant challenge for 5G systems. “Within the same channel bandwidth, the proposed transmitter can transmit six to ten times higher data rate,” Wang said. “Integrating the antenna gives us more degrees of freedom to explore design innovation, something that could not be done before.”
The new designs have been implemented in 45-nanometer CMOS SOI IC devices and flip-chip packaged on high-frequency laminate boards, where testing has confirmed a minimum two-fold increase in energy efficiency, Wang said. The antenna electronics co-design is enabled by exploring the unique nature of multi-feed antennas.
“An antenna structure with multiple feeds allows us to use multiple electronics to drive the antenna concurrently. Different from conventional single-feed antennas, multi-feed antennas can serve not only as radiating elements, but they can also function as signal processing units that interface among multiple electronic circuits,” Wang explained. “This opens a completely new design paradigm to have different electronic circuits driving the antenna collectively with different but optimized signal conditions, achieving unprecedented energy efficiency, spectral efficiency and reconfigurability.”
The cross-disciplinary co-design could also facilitate fabrication and operation of multiple transmitters and receivers on the same chip, allowing hundreds or even thousands of elements to work together as a whole system. “In massive MIMO systems, we need to have a lot of transmitters and receivers, so energy efficiency will become even more important,” Wang noted.
Having large numbers of elements working together becomes more practical at millimeter wave frequencies because the wavelength reduction means elements can be placed closer together to achieve compact systems, he pointed out. These factors could pave the way for new types of beamforming that are essential in future millimeter wave 5G systems.
US ARL exploring 3D printing antennas
Larry Holmes, the principal investigator for materials and technology development in additive manufacturing at the U.S. Army Research Laboratory (ARL), is exploring potential uses for additive manufacturing of 3D printed plastic antennas. Unlike conventional antennas that are made of conductive material University of Texas at El Paso is exploring the use of plastic or even ceramic.
Holmes explains that the 3D printed antenna would work “by the dielectrics that are internal to the structure, solely because of the shapes you can make through 3D printing.” That is, the antenna would function electronically through its geometric composition, meticulously designed with 3D technology, rather than through its material, plastic being a non-conductive material.
The benefits of having an additively manufactured antenna include being able to manufacture them on the spot rather than having parts and equipment imported, as Holmes puts it, the antenna would “help us reduce logistics and the logistics trail but also help with signature management.
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