Broadband Devices Research Articles

Electromechanical characterization of piezoelectric polymer thin films in a broad frequency range

Piezoelectric materials are usually characterized using resonant methods. However, piezoelectric polymers are used in broadband devices, thus requiring characterization over a wide range of frequencies. In this work, we present a non-resonant method for the broadband electromechanical characterization of piezoelectric polymer thin films. The procedure is based on measuring the complex capacitance of a sample of known geometry under three conditions: free, blocked and immersed in a fluid of known acoustic properties. The behaviour of the sample under study is modelled as a one-dimensional transducer and treated as a two-port network that relates the measurable electrical and mechanical variables. Also, the sample is considered as a free-space radiator when immersed in a fluid. The method determines the intensive and the equivalent circuit parameters of piezoelectric polymer films, allowing the characterization of elastic and electrical properties in a broad frequency range.In order to test the method, we performed isothermal capacitance measurements on a sample of poly(vinylidene fluoride) at a temperature of 298 K. The sample was measured along the direction of the poling field and in the frequency range from 10 Hz to 10 MHz. The results given by the method agree with those reported by other authors.

Energy-Efficient Power Allocation for Delay-Sensitive Multimedia Traffic Over Wireless Systems

With the extremely high penetration rate of wireless broadband devices, the telecommunication industry predicts that the mobile data traffic will double almost every year for the next five years with more than two-thirds of the future traffic being mobile video. This trend clearly indicates that future mobile broadband networks will face the dual challenge of supporting large data volumes while providing reliable service for delay-sensitive mobile multimedia streams. This explosive demand for mobile multimedia communications has significantly increased not only spectrum requirements but also energy consumption. Energy-efficient communication is becoming a prime concern for mobile multimedia communications partially due to the fact that improvements in battery technology occur on a much slower scale than gains in processing power and energy consumption of electronic devices. Furthermore, the ever-increasing demand for wireless services and ubiquitous network access comes at the expense of a growing carbon footprint for the mobile wireless communication industry. This paper addresses resource allocation to maximize the energy efficiency of a wireless link under statistical quality-of-service (QoS) constraints for mobile multimedia traffic. In the energy-efficiency analysis, both circuit and transmit power values of mobile devices are taken into account. The joint impact of statistical QoS constraints, underlying circuit power consumption, transmission power, and spectral bandwidth is considered. The unique globally optimal power allocation scheme for delay-sensitive multimedia traffic is characterized. Intuition about optimal strategies is obtained by looking at both the low-signal-to-noise-ratio (SNR) regime and the high-SNR regime.

Non-reciprocal and highly nonlinear active acoustic metamaterials

Unidirectional devices that pass acoustic energy in only one direction have numerous applications and, consequently, have recently received significant attention. However, for most practical applications that require unidirectionality at audio and low frequencies, subwavelength implementations capable of the necessary time-reversal symmetry breaking remain elusive. Here we describe a design approach based on metamaterial techniques that provides highly subwavelength and strongly non-reciprocal devices. We demonstrate this approach by designing and experimentally characterizing a non-reciprocal active acoustic metamaterial unit cell composed of a single piezoelectric membrane augmented by a nonlinear electronic circuit, and sandwiched between Helmholtz cavities tuned to different frequencies. The design is thinner than a tenth of a wavelength, yet it has an isolation factor of >10 dB. The design method generates relatively broadband unidirectional devices and is a good candidate for numerous acoustic applications.

Dual-band tunable negative refractive index metamaterial with F-Shape structure

AbstractThis paper presents a negative refractive index tunable metamaterial based on F-Shape structure which is capable of achieving dual-band negative permeability and permittivity, thus dual-band negative refractive index. An electromagnetic simulation was performed and effective media parameters were retrieved. Numerical investigations show clear existence of two frequency bands in which permeability and permittivity both are negative. The two negative refractive index bandwidths are from 23.8 GHz to 24.1 GHz and from 28.3 GHz to 34.9 GHz, respectively. The geometry of the structure is simple so it can easily be fabricated. The proposed structure can be used in multiband and broad band devices, as the band range in second negative refractive index region is 7 GHz, for potential applications instead of using complex geometric structures and easily tuned by varying the separation between the horizontal wires.

A qualitative case study of telehealth for in-home monitoring to support the management of type 2 diabetes

The present study formed part of a randomised controlled trial of telehealth for in-home monitoring to support people with poorly controlled type 2 diabetes. We explored the experiences of patients and healthcare practitioners, and their perceptions of the telehealth model of care used in the trial. In addition to their usual diabetes care, participants receive diabetes care from a diabetes educator nurse via an in-home broadband communication device. On average, each patient participated in 14 videoconferences with a diabetes care coordinator during the 12-month trial period. Qualitative data was collected from two general practices and included semi-structured interviews and document review of patient clinical notes. A total of 12 people were interviewed: 8 health practitioners and 4 patients. Patients and health practitioners expressed a high level of satisfaction with the model of care provided. Patients also reported positive health and social outcomes as a result of being involved in the trial and indicated that in the main they had achieved their goals and were happy with their progress over the 12-month period. Analysis of interviews revealed three broad elements associated with the implementation of telehealth: interpersonal factors, operational problems and the wider health system context within which the general practices and trial team were operating. The findings suggest that adopting telehealth in the management of type 2 diabetes can lead to improved diabetes control, but more support is required to ensure sustainability and widespread implementation.

Multi-element Josephson structures for implementing broadband devices

It is proposed the solution of an urgent problem of developing broadband superconducting devices via implementation of multi-element Josephson structures with an expanded dynamic range (due to the increase in the number of cells) and required high linearity of the transfer function of magnetic signal into voltage (due to the use of specially designed Josephson cells with a highly linear voltage response). Active electrically small antenna prototypes based on the proposed multi-element structures are experimentally studied.

A System Dynamics Approach to Quantitatively Analyze the Effects of Mobile Broadband Ecosystem’s Variables on Demands and Allocation of Wireless Spectrum for the Cellular Industry

Radio spectrum is an encumbered and finite resource. Perception of radio spectrum scarcity has been linked, sometimes linearly, to the higher demand of mobile data services and the greater market penetration of mobile broadband devices. Cellular operators worldwide have been asking to allocate more spectrum to support this demand. To validate the “spectrum scarcity” notion, various elements of the wireless ecosystem, including network infrastructure, spectral efficiency of mobile technologies, and data offloading via unlicensed spectrum need to be appraised; and their effects on “spectrum utilization” need to be understood. Research presented here takes a system dynamics approach to study dynamic behaviour among these elements and their effects on usage of spectrum through sensitivity analysis. A stock-and-flow model-based simulation is employed for hypotheses testing to justify the need for more spectrum. Simulation results show that mobile data demand can exceed the current capacity of cellular networks causing a spectrum deficit if apt planning of spectrum policies and appropriate infrastructure investment are delayed.

A Dual‐Resonant Metamaterial in Terahertz Regime

ABSTRACTThe design, fabrication, and measurement of a dual‐band terahertz (THz) metamaterial based on gallium arsenide substrate are presented. The proposed subwavelength structure provides two distinct electrical resonances near 0.39 and 0.59 THz. Measured results obtained from the THz time‐domain spectroscopy show good agreement with the simulation results. Effective medium parameters show negative values of permittivity during two frequency bands of 0.38–0.44 THz and 0.59–0.64 THz. This metamaterial is expected to enhance the realization of broadband and multiband functional devices in THz regime. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2095–2099, 2013

What Teachers Need to Know About Augmented Reality Enhanced Learning Environments

Augmented reality (AR) enhanced learning environments have been designed to teach a variety of subjects by having learners act like professionals in the field as opposed to students in a classroom. The environments, grounded in constructivist and situated learning theories, place students in a meaningful, non-classroom environment and force them to collaborate with each other in order to solve an ill-defined problem. AR content, accessed via a mobile broadband device (MBD) such as a phone or tablet, is used to guide the learning experiences. Student participants have reported an increased interest in the settings of the experiences and have expressed a positive attitude towards this innovative form of instructional delivery. Using newly available software loaded on MBDs, teachers and/or students can design and share AR enhanced learning environments that are tied to unique places in their communities.

Impacts of the Broadband Telecommunication Opportunities Program in Michigan Urban Communities

The American Recovery and Reinvestment Act of 2009 (ARRA) was used to increase broadband adoption and utilization across the United States as part of the economic recovery after the 2008 recession. Part of this act implemented a program called the Broadband Telecommunication Opportunities Program (BTOP), which focused on expanding effective broadband utilization in underserved communities through the development of library-based public computing centers and other educational outreach. This paper reports the results of two waves of surveys of 400 participants each, spanning 18 months, which were conducted in urban communities in Michigan served by libraries participating in a $6M BTOP grant project to upgrade their public Internet resources. The surveys tracked perceptions of broadband services and their utilization in public libraries, residences, and other community locations. One of the major questions going into this project was whether or not urban poor residents were adopting and utilizing broadband through either a private connection or a public connection. If the former, then results would indicate a similar trend among urban poor as seen in the rest of the world. That is, home adoption of fixed landline broadband connections will be lower in our sample than in more wealthy areas, but mobile adoption of broadband devices and services would be increasing. The second question, with libraries across the U.S. losing funding and reducing hours, would be whether the implementation of programs and new computing centers from the ARRA BTOP increase broadband adoption and utilization leading to economic recovery in these urban poor communities?Over three-fifths of those surveyed as the project drew to a close were aware of the public computing center initiative at their local library, although only about one tenth were active participants. Among those using library computers at the time of the final survey, about a fourth indicated that they had noticed an improvement in library computing facilities. The above findings suggest that, while library access, public computing centers, and broadband awareness increases adoption of broadband at the home and mobile level. Thus, in order to increase broadband use among urban poor, other considerations may need to be adopted in addition to increased outreach and awareness projects about library broadband use.

A COMPACT, LOW-PROFILE, ULTRA-WIDEBAND ANTENNA UTILIZING DUAL-MODE COUPLED RADIATORS

In this paper, we present a low-proflle, compact, ultra- wideband antenna that uses a set of closely coupled radiators. The system of two coupled radiators has two difierent linearly independent modes of operation with complementary frequency bands of operation. These include the difierential mode and the common mode of operation. When the antenna is excited in the common mode of operation, it acts as an ultra-wideband (UWB) antenna covering a broad frequency band. When excited in the difierential mode, the antenna operates as a wideband dipole in a frequency range below that of the common mode. Thus, by appropriately combining the two modes using a suitably designed feed network, the bandwidth of the antenna can be extended and its lowest frequency of operation is reduced. Mode combining is achieved with a feed network that employs a frequency-dependent phase shifter. Using this feed network, the two modes of the antenna are combined and a single-port broadband device is achieved that has a bandwidth larger than that of either the common or the difierential mode individually. A prototype of the antenna is fabricated and experimentally characterized.

Randomised controlled trial of an in-home monitoring intervention to improve health outcomes for type 2 diabetes: study protocol.

Type 2 diabetes is a leading cause of death and morbidity and is a health priority in Australia. This randomised controlled trial will explore whether remote access to clinical care, supported by telehealth technologies over high speed broadband, leads to improved diabetes control in a way that benefits patients, carers and clinicians and improves the overall health system. People in the intervention arm of the trial will receive additional diabetes care from a care coordinator nurse via an in-home broadband communication device that can capture clinical measures, provide regular health assessments and videoconference with other health professionals when required. Patients in the control arm of the trial will receive usual care from their GP and participate in the clinical measurement and quality of life components of the evaluation. The trial evaluation will include biomedical, psychological, self-management and quality of life measures. Data on utilisation rates and satisfaction with the technology will be collected and cost -effectiveness analyses undertaken. The role of this technology in health care reform will be explored.

Optical Properties of Chiral Three-Dimensional Plasmonic Oligomers at the Onset of Charge-Transfer Plasmons

We demonstrate strong chiral optical response in three-dimensional chiral nanoparticle oligomers in the wavelength regime between 700 and 3500 nm. We show in experiment and simulation that this broad-band response occurs at the onset of charge transfer between the individual nanoparticles. The ohmic contact causes a strong red shift of the fundamental mode, while the geometrical shape of the resulting fused particles still allows for an efficient excitation of higher order modes. Calculated spectra and field distributions confirm our interpretation and show a number of interacting plasmonic modes. Our results deepen the understanding of the chiral optical response in complex chiral plasmonic nanostructures and pave the road toward broad-band chiral optical devices with strong responses, for example, for chiral plasmon rulers or sensing applications.

Experimental study of hydraulic engine mounts using multiple inertia tracks and orifices: Narrow and broad band tuning concepts

Hydraulic engine mount tuning concepts with one inertia track and one decoupler are well understood. However, the dynamic response with multiple tracks or orifices is not. To overcome this void in the literature, dynamic tuning concepts of hydraulic engine mounts, with emphasis on multiple (n-)inertia tracks/orifices, are experimentally examined. A new prototype mount concept is designed, built, and experimentally evaluated in a controlled manner. Refined linear time-invariant models of fixed decoupler-type designs are developed to critically assess the dynamic stiffness measurements and to explore a family of alternate designs. Three narrowband devices are investigated for accurately predicting the frequencies corresponding to peak loss angles for the first time, in addition to examining and validating an n=3 track mount. Two broadband devices are also successfully evaluated by tuning damping introduced by orifice-type tracks. A special broad-tuned design utilizing a controlled ‘leakage’ path flow area is then suggested, and the role of fluid resistance in achieving the desired performance is clarified. Finally, a production mount with unknown configuration is diagnosed using the proposed models with n tracks.

Block Transceivers: OFDM and Beyond

The demand for data traffic over mobile communication networks has substantially increased during the last decade. As a result, these mobile broadband devices spend the available spectrum fiercely, requiring the search for new technologies. In transmissions where the channel presents a frequency-selective behavior, multicarrier modulation (MCM) schemes have proven to be more efficient, in terms of spectral usage, than conventional modulations and spread spectrum techniques. The orthogonal frequency-division multiplexing (OFDM) is the most popular MCM method, since it not only increases spectral efficiency but also yields simple transceivers. All OFDM-based systems, including the single-carrier with frequency-division equalization (SC-FD), transmit redundancy in order to cope with the problem of interference among symbols. This book presents OFDM-inspired systems that are able to, at most, halve the amount of redundancy used by OFDM systems while keeping the computational complexity comparable. Such systems, herein called memoryless linear time-invariant (LTI) transceivers with reduced redundancy, require low-complexity arithmetical operations and fast algorithms. In addition, whenever the block transmitter and receiver have memory and/or are linear time-varying (LTV), it is possible to reduce the redundancy in the transmission even further, as also discussed in this book. For the transceivers with memory it is possible to eliminate the redundancy at the cost of making the channel equalization more difficult. Moreover, when time-varying block transceivers are also employed, then the amount of redundancy can be as low as a single symbol per block, regardless of the size of the channel memory. With the techniques presented in the book it is possible to address what lies beyond the use of OFDM-related solutions in broadband transmissions. Table of Contents: The Big Picture / Transmultiplexers / OFDM / Memoryless LTI Transceivers with Reduced Redundancy / FIR LTV Transceivers with Reduced Redundancy

Topological insulator nanostructures for near-infrared transparent flexible electrodes

Topological insulators are an intriguing class of materials with an insulating bulk state and gapless Dirac-type edge/surface states. Recent theoretical work predicts that few-layer topological insulators are promising candidates for broadband and high-performance optoelectronic devices due to their spin-momentum-locked massless Dirac edge/surface states, which are topologically protected against all time-reversal-invariant perturbations. Here, we present the first experimental demonstration of near-infrared transparent flexible electrodes based on few-layer topological-insulator Bi(2)Se(3) nanostructures epitaxially grown on mica substrates by means of van der Waals epitaxy. The large, continuous, Bi(2)Se(3)-nanosheet transparent electrodes have single Dirac cone surface states, and exhibit sheet resistances as low as ~330 Ω per square, with a transparency of more than 70% over a wide range of wavelengths. Furthermore, Bi(2)Se(3)-nanosheet transparent electrodes show high chemical and thermal stabilities as well as excellent mechanical durability, which may lead to novel optoelectronic devices with unique properties.

Control of Plasmonic Superradiance in Metallic Nanoparticle Assembly by Light-Induced Force and Fluctuations.

The possibility of simultaneous control of the configuration and optical functions of a metallic nanoparticle (NP) assembly by light-induced force (LIF) and thermal fluctuations has been demonstrated on the basis of self-consistent theory of LIF and nonequilibrium dynamics. It has been clarified that the NPs are arranged parallel to the polarization of the focused laser beam under the balance of LIF and the electrostatic repulsive force due to the ions on the surface of NPs. Particularly, in such a NP assembly consisting of high-density NPs, the light-scattering rate (radiative decay) of localized surface plasmon polaritons (LSPPs) can be drastically enhanced to be greater than 100 meV (10 times that of single NPs), and the spectral width is also greatly broadened due to the superradiance effect. The results will provide a foundation of the principles for designing a NP assembly with controllable light scattering for highly efficient broad-band light energy conversion devices.

The Transformation of Personal Communications and the Erosion of Traditional Voice Provider Dominance

The paper examines the evolution of personal communications and the implications for traditional switched voice services provided by incumbent local exchange carriers. As the nature of personal communications has evolved and become increasingly competitive, incumbent local exchange carrier dominance of communications through the provision of voice telephony has eroded, and therefore so has the primary rationale for regulating traditional voice telephony. The primary focus of this analysis is residential communications. In particular, mobile and packet-switched broadband technologies have accelerated the adoption of alternative voice access methods for residential consumers, including the adoption of wireless telephony, interconnected Voice over Internet Protocol (VoIP), and competitive switched telephony as alternatives to switched voice telephony provided by incumbent local exchange carriers. In addition to access, mobile and broadband technologies have enabled a shift toward entirely new application-level modes of communication, such as text messaging, instant messaging, email, social networking, computer telephony, and Internet video conferencing. While these shifts in access-based and application-based alternatives have occurred incrementally over many years, the transformations — in the way consumers communicate with each other, plus the associated industry responses and changes industry structure—have been substantial. The analysis measures the magnitude of the consumer shift away from incumbent switched voice. It builds up incrementally a measurement of the shift away from incumbent switched voice, from a very conservative approach focused simply on access technologies to more comprehensive approaches taking into consideration application-level communications alternatives. The most conservative measure examines access choices for primary lines at the household level. It is possible to eliminate the primary line constraint and focus on total lines or connections. Extended to wireless, this is the most generous access-based approach, given multiple wireless connections per household. We next expand the measurement of alternatives to voice to include application-level communications modes. This more comprehensive approach takes into account the ways that technology continues to change the nature of personal communication. For example, there would appear to be greater emphases on time shifting, place shifting, device-shifting, format shifting, multi-party messaging, and integration with online applications and activities. After a discussion of measurement challenges, the analysis utilizes national data to map out the shift in demand for personal communications. In particular we map the extent of demand for communications at the application level by measuring the diffusion of broadband and mobile devices, networks, and applications compared with traditional voice access methods. Once we have developed reasonable measurements to capture the shift to alternative communications methods, we discuss opportunities for assessing wireline voice providers’ competitive responsiveness, taking into consideration the benefits and limitations of traditional measures.

State of the Art in 60-GHz Integrated Circuits and Systems for Wireless Communications

This tutorial presents an overview of the technological advances in millimeter-wave (mm-wave) circuit components, antennas, and propagation that will soon allow 60-GHz transceivers to provide multigigabit per second (multi-Gb/s) wireless communication data transfers in the consumer marketplace. Our goal is to help engineers understand the convergence of communications, circuits, and antennas, as the emerging world of subterahertz and terahertz wireless communications will require understanding at the intersections of these areas. This paper covers trends and recent accomplishments in a wide range of circuits and systems topics that must be understood to create massively broadband wireless communication systems of the future. In this paper, we present some evolving applications of massively broadband wireless communications, and use tables and graphs to show research progress from the literature on various radio system components, including on-chip and in-package antennas, radio-frequency (RF) power amplifiers (PAs), low-noise amplifiers (LNAs), voltage-controlled oscillators (VCOs), mixers, and analog-to-digital converters (ADCs). We focus primarily on silicon-based technologies, as these provide the best means of implementing very low-cost, highly integrated 60-GHz mm-wave circuits. In addition, the paper illuminates characterization techniques that are required to competently design and fabricate mm-wave devices in silicon, and illustrates effects of the 60-GHz RF propagation channel for both in-building and outdoor use. The paper concludes with an overview of the standardization and commercialization efforts for 60-GHz multi-Gb/s devices, and presents a novel way to compare the data rate versus power efficiency for future broadband devices.

Negative permeability characterization of gyrotropic hexaferrite in the millimeter wave band for engineering of double-negative devices

Thin, square, hexaferrite plates, with magnetization normal to the broad faces, are investigated as fundamental components for creating metamaterials with double-negative character in the millimeter wave band. The intrinsic, chiral, magneto-optical properties of a newly discovered special hexaferrite ceramic (named FB6H), are characterized using a general-purpose, free-space, quasioptical, millimeter wave reflectometer that measures with high numerical and operational efficiency to high accuracy. The FB6H material proves itself to be amenable to possible adaption for delivery of low-loss, broadband double-negative devices and for more challenging reaches into the millimeter/submillimeter wave band due to its stable, broadband negative permeability and promising natural, low-loss properties.