High Frequency Bandwidth Research Articles

DTV/LTE antennas with no physical structure for laptop computers

This paper proposes a DTV/LTE antenna design without physical structure for laptop computers. By changing the laptop’s right revolving axis to a non-conductor material and exciting several dipoles and loop paths formed by the display, keyboard ground plane and metal revolving axis using a feed matching circuit at an appropriate position of the slot on the hinge to cover the frequency bands for DTV (470–862 MHz) and LTE (698–960 MHz, 1710–2690 MHz). The feed matching circuit is fitted to the keyboard ground plane adjacent to the hinge. It consists of a 3.6 nH chip inductor and a 0.2 pF chip capacitor to improve the high frequency matching and increase the high frequency bandwidth. The antenna can cover the frequency bands required by DTV and LTE, and the measured antenna efficiency in the operational frequency band is also better than 50%.

Untreated adolescent idiopathic scoliotic girls display altered balance modalities during self-paced voluntary body sways compared to able-bodied girls

IntroductionThis study investigated self-paced voluntary oscillations of scoliotic and non-scoliotic girls. Temporal variables and frequency coherence were calculated for the overall, low and high frequency bandwidths of the center of pressure excursions and free-moment to identify which variables best describe sway balance modalities in both groups. MethodsTwenty-three girls with adolescent idiopathic moderate scoliosis (spinal curves to the right) formed the scoliotic group and 19 matched able-bodied girls formed the non-scoliotic group. Each girl performed self-paced voluntary medio-lateral and antero-posterior sways while standing on a force platform. Center of pressure displacements, out of plane deviation and free-moment were measured and their frequency content calculated. The magnitude of the coherence was calculated for each signal pairs for three frequency ranges. ResultsIn both sway conditions, the center of pressure excursion parameters were on average 28% higher for the scoliotic group. Factor analysis revealed that balance modalities were essentially based on frequency coherence pair interactions whereas temporal parameters play a secondary role. However, these balance modalities were altered in the scoliotic group. They relied essentially on 2 additional principal components and 3 additional variables reflecting a fine tuning of the control mechanism to maintain dynamic balance. InterpretationScoliotic girls appear to be performing a wide ellipsoidal trajectory when performing whole body oscillations. Superfluous variables could be related to the difficulty in preserving balance during body sway tasks and could parasitize the scoliotic dynamic control balance modalities. Self-paced voluntary sways could be an appropriate complementary balance test for untreated scoliotic girls.

Evaluation of vibration-induced flow in high bandwidth frequency vibration

Evaluation of vibration-induced flow in high bandwidth frequency vibration

Design of Solar Blind Photodetectors for Communication with Green Signal (λ= 0.532µm) in Space. Part II

The areas of Free Space Optical (FSO) communication and high-speed Visible Light Communication (VLC) offer potential for very high-speed data transmission. Favorable attributes including high frequency and wider bandwidths that can enable transmission speeds of the order 100Gb/s, associated with the visible region of the electromagnetic spectrum make it preferable for allowing communication among satellites and ground stations, under-water communication, etc. However, limitations associated with spectral absorption characteristics of the propagating media have stymied further development of such technologies.
 Aims: Commercial lasers operating in red, green and blue lights combined with three photodetectors, each sensitive to selected wavelengths (colors) present basics of long-distance optical communication system. The current study (Part II) depicts the design and operation of a solar-blind photodetector capable to work explicitly with green wavelength of 532nm.
 Study Design and Results: The structure of the solar-blind photodetector consists of two sections made of InxGa1-xN (Indium Gallium Nitride) heterostructure, (where x denotes the mole fraction)-a filter and a double barrier tunneling diode. The topmost approximately 1µm thick section acts as a filter and as a p-i-n solar cell providing the required voltage bias to the photodiode. The filter with Eg (Energy Band Gap)=2.33eV absorbs all photons having wavelengths shorter than 532nm. The double barrier tunneling photodiode which comprises the lower section operates with Eg=2.28eV. It consists of an n-type lightly doped quantum well having a width of 2.5nm housed between two lightly doped barriers of 10nm thickness. The 0.12µm topmost and bottom regions of the photodiode are doped with p and n (2×105cm-3) type impurities, respectively. The illuminated cross-section area of the device is finalized at 1mm2.

Energy Efficient Resource Allocation in Terahertz Downlink NOMA Systems

Terahertz (THz) band has attracted considerable interest recently due to its superior high frequency and large available bandwidth. THz could act a vital part in the sixth generation (6G) mobile communication networks. In this paper, we introduce the downlink non-orthogonal multiple access (NOMA) technology into THz band small cell networks, where the total performance is optimized considering the two key enabling technologies. In order to decrease the energy consumption triggered by increasing of wireless services, we pay great attention to energy efficiency (EE) optimization and resource allocation in the THz-NOMA downlink systems by solving the subchannel assignment and power optimization. We first exploit a channel model for the THz-NOMA downlink system by using the key features of THz-NOMA networks. Then we utilize Dinkelbach-style algorithm to solve the resource allocation problem and decompose it into two subproblems. A subchannel assignment algorithm and a power optimization based on alternative direction method of multipliers (ADMM) algorithm are developed to get the solution. Finally, to embody the strengths of THz-NOMA performance, we compare our proposed schemes against the conventional schemes. Simulation results yield substantially higher EE and further prove the availability of our proposed schemes.

Soft-Start Procedure for a Three-Stage Smart Transformer Based on Dual-Active Bridge and Cascaded H-Bridge Converters

Power electronics based three-stage smart transformers (STs) can be seriously damaged by inrush currents and overvoltages during the start-up phase if the control of the stages is not correctly coordinated. Hence, it is crucial to design properly the start-up procedure, especially in case of modular architectures with distributed dc-links. The design of the start-up procedure depends on the ST power stages topologies, their control systems, and the operation modes. This article proposes a soft-shift start modulation technique that allows to limit the inrush current in the dc/dc isolation stage during the dc-link capacitors precharging. A fast voltage-balancing control, performed by the dc/dc isolation stage, is introduced to avoid overvoltages and unbalanced voltage conditions among the different power cells. Under the proposed method, fast control dynamics is guaranteed thanks to the high frequency bandwidth of the dc/dc isolation stage converters. Theoretical analysis, based on a detailed small signal model of the ST, and simulations are used to demonstrate the principle of the operation. Experimental results, carried out in an ST prototype, confirm the performances of proposed solution in realizing a smooth start-up without voltage/current overshoots.

Arbitrary-order fractance approximation circuits with high order-stability characteristic and wider approximation frequency bandwidth

This paper discusses a novel rational approximation algorithm of arbitrary-order fractances, which has high order-stability characteristic and wider approximation frequency bandwidth. The fractor has been exploited extensively in various scientific domains. The well-known shortcoming of the existing fractance approximation circuits, such as the oscillation phenomena, is still in great need of special research attention. Motivated by this need, a novel algorithm with high order-stability characteristic and wider approximation frequency bandwidth is introduced. In order to better understand the iterating process, the approximation principle of this algorithm is investigated at first. Next, features of the iterating function and frequency-domain characteristics of the impedance function calculated by this algorithm are researched, respectively. Furthermore, approximation performance comparisons have been made between the corresponding circuit and other types of fractance approximation circuits. Finally, a fractance approximation circuit with the impedance function of negative 2 &#x002F 3-order is designed. The high order-stability characteristic and wider approximation frequency bandwidth are fundamental important advantages, which make our proposed algorithm competitive in practical applications.

A novel MEMS triboelectric energy harvester and sensor with a high vibrational operating frequency and wide bandwidth fabricated using UV-LIGA technique

A novel triboelectric energy harvesting (TEH) and sensing system scaled down to microelectromechanical systems (MEMS) size is presented. The design is structurally optimized for harvesting the highest average power and power density while ensuring the structural robustness. Unlike traditional triboelectric energy harvesters, this design results in a high operating frequency with a wide bandwidth. Adoption of MEMS fabrication techniques including the use of spin-coated Teflon AF rather than a Teflon sheet, adaptation of UV-LIGA (Ultra-Violet Lithographie, Galvanoformung, Abformung) with modifications and implementation of a thick polyimide sacrificial layer make the fabrication process unique. If excited by ±9.33 g external vibration with a frequency of 1.15 kHz, the TEH can generate 0.179 μW average power and 0.597 μW peak power at an optimum resistive load of 256 kΩ. The peak surface power density, volumetric power density and acceleration-normalized volumetric power density reach 3.98 μWcm−2, 2.64 mWcm-3 and 30.3 μWcm-3/g2, respectively. While the surface power density of the presented TEH is moderate, the volumetric power density and acceleration-normalized volumetric power density are quite competitive among the state-of-the-art designs. The TEH also demonstrates a wide operating frequency bandwidth of 920 Hz. If operated as an accelerometer, the device shows a linear sensitivity of 43 mV/g. Although the simulation predicts the optimum operating frequency and load resistance of the system to be at 800 Hz and 10 MΩ, respectively, the experimental results demonstrate these values to be at 1150 Hz and 256 KΩ. A few fabrication anomalies, most notably the notching in the Teflon layer and bowing of the proof-mass, are responsible for this deviation. In addition, a distortion is observed in the simulated output voltage profile which is not present in the experimental output voltage profile due to the presence of the parasitic capacitance in the experimental circuit. The aforementioned triboelectric energy harvester can have specific applications in the sensor and actuator systems in the aircraft industry as well as in the automobile industry, micro-robotic systems, prosthetic systems, and sensor nodes in the internet of things (IoT) due to its operating frequency and bandwidth range.

Fundamental and environmental contributions to the cyclostationary third moment of current fluctuations in a tunnel junction

Current fluctuations generated by tunnel junctions are known to be non-Gaussian. However, this property is lost when fluctuations are measured at high frequency and limited bandwidth. We show that the quadratures of the electric field generated by a tunnel junction at frequency $f$ displays third order correlations, i.e. skewness, when the junction is electrically driven at $3f$, revealing the Poisonnian statistic of charge transfer by the barrier even at short time-scales. In addition to this intrinsic contribution from the junction, we observe extra correlations induced by the environmental noise at frequency $f$ as well as a feedback effects coming from the environmental impedance not only at frequency $f$ but also at some multiples of $f$.

Real-time terahertz meta-cryptography using polarization-multiplexed graphene-based computer-generated holograms

Abstract As one of the cutting-edge technologies in advanced information science, wave-based cryptography is a prerequisite to enable a plethora of secure encrypting platforms which can be realized by smart multiplexing techniques together with suitable metasurface holograms (meta-holograms). Here, relying on the polarization multiplicity and re-writability of a computer-generated meta-hologram, a fully secure communication protocol is elaborately developed at the terahertz spectrum to host unique merits for exploring real-time metasurface-based cryptography (meta-cryptography) where highly restricted access of information is imposed. The proposed meta-cryptography exploits two dynamic near-field channels of a meta-hologram whose information can be instantaneously re-written without any polarization rotation and with high contrast and acceptable frequency bandwidth. The computer-generated meta-hologram is constructed based on the weighted Gerchberg–Saxton algorithm via a two-dimensional array of vertical graphene strips whose anisotropic reflection is merely determined by external biasing conditions. Several illustrative examples have been presented to demonstrate the perfect secrecy and polarization cross-talk of the proposed meta-cryptography. Numerical simulations corroborate well our theoretical predictions. As the first demonstration of dynamic THz meta-cryptography, the meta-hologram information channels can be deciphered into manifold customized messages which would be instrumental in data storage systems offering far higher data rates than electronic encryption can deliver.

Modeling and prototype experiment of a monolithic 3-PUU parallel micromanipulator with nano-scale accuracy

This paper presents the design and experimental investigation of a piezo-driven monolithic compliant 3-PUU (1 prismatic joint (P-joint) and 2 universal joints (U-joints)) XYZ micro/nano manipulator with a high bandwidth frequency and a large workspace. The manipulator is manufactured using a 3D-printing technique, thus a monolithic structure is guaranteed. This feature allows the manipulator to work smoothly with high resolution, accuracy, and repeatability, and simultaneously, it avoids all the deficiencies of non-monolithic designs such as backlash, wear, and friction. Analytical and computational studies are conducted to investigate and confirm the performances of the manipulator. Additionally, an experimental study is performed to verify the analytical and computational results. The workspace is calculated using the three methods, and their relative errors along each axis are shown to validate the accuracy of the results. The tracking performances of the manipulator are validated in a feedback control strategy. Moreover, the proposed manipulator demonstrates the motion resolution of 23 nm, 24 nm, and 18 nm along X, Y, and Z axes, respectively. Finally, the experimental frequency test supports the computational results and confirms the manipulator’s high bandwidth frequency.

Transmitting audio via fiber optics under nonlinear effects and optimized tuning parameters based on Co-simulation of matlab and optisystemTM

Limitations of conventional wires such as copper wires are causing dispersion and distortion of the message signal for long distances communication especially for the wide bandwidths. The ability of fiber optic to overcome this problem is making it a dominant transmission medium. Despite of this major positive attribute of optic fibers, there is still a downside for using the fiber optic communication; that is the nonlinearity problem especially at the very high frequency bandwidth. For the first time, a desigen of an audio signal is suggested and executed in MatLab with an integration with OptiSystemTM software to discuss and solve this issu. The audio signal is then transmitted in different shapes of modulation signals (NRZ, RZ & RC) for different distances (100 km & 75 km) via a fiber optic media to be received in a receiving part of the simulated system. Three tests are used to do so. The first is the Quality-factor (Q-Factor) against the received power, second test is eye diagram performance and finally is the measuring of the amplitude of output (received) signal for each modulation signal shape using the Oscilloscope Visualizer. The NZR modulation signal was found to be the best one of the three used signals’ types in all three tests. The Q-factor for NRZ pulse shape (=12) was higher than that for RZ (=10) and RC (=8) for a 100 km distance at the same received power level.

Constant Temperature Anemometer with Self-Calibration Closed Loop Circuit

In this paper, a Micro-Electro-Mechanical Systems (MEMS) calorimetric sensor with its measurement electronics is designed, fabricated, and tested. The idea is to apply a configurable voltage to the sensitive resistor and measure the current flowing through the heating resistor using a current mirror controlled by an analog feedback loop. In order to cancel the offset and errors of the amplifier, the constant temperature anemometer (CTA) circuit is periodically calibrated. This technique improves the accuracy of the measurement and allows high sensitivity and high bandwidth frequency. The CTA circuit is implemented in a CMOS FD-SOI 28 nm technology. The supply voltage is 1.2 V while the core area is 0.266 mm2. Experimental results demonstrate the feasibility of the MEMS calorimetric sensor for measuring airflow rate. The developed MEMS calorimetric sensor shows a maximum normalized sensitivity of 117 mV/(m/s)/mW with respect to the input heating power and a wide dynamic flow range of 0–26 m/s. The high sensitivity and wide dynamic range achieved by our MEMS flow sensor enable its deployment as a promising sensing node for direct wall shear stress measurement applications.

Design and Verification of VFTO Differentiating-Integrating Measurement Equivalent Circuit

Operation of isolating switches and circuit breakers in fully enclosed gas insulated substations (GIS) produces very fast transient overvoltage (VFTO). According to IEC61321-1, VFTO contains four frequency components with frequencies ranging from 0.1 MHz to 100 MHz. Therefore, the VFTO measurement system needs to have good transient response and steady state response and puts high requirements on the measurement frequency band. As a measurement method that does not need to modified GIS, the differentiating-integrating measurement system has the characteristics of high frequency bandwidth and high voltage divider ratio. In this paper, the theoretical derivation and numerical calculation of the equivalent circuit of differentiating-integrating measurement are carried out, and the simulation of time domain, frequency domain and synthetic VFTO waveform as excitation source was constructed, and its performance is fully verified, which proves that this system can meet the needs of VFTO measurement.

Ionospheric Narrowband and Wideband HF Soundings for Communications Purposes: A Review.

High Frequency (HF) communications through ionospheric reflection is a widely used technique specifically for maritime, aeronautical, and emergency services communication with remote areas due to economic and management reasons, and also as backup system. Although long distance radio links can be established beyond line-of-sight, the availability, the usable frequencies and the capacity of the channel depends on the state of the ionosphere. The main factors that affect the ionosphere are day-night, season, sunspot number, polar aurora and earth magnetic field. These effects impair the transmitted wave, which suffers attenuation, time and frequency dispersion. In order to increase the knowledge of this channel, the ionosphere has been sounded by means of narrowband and wideband waveforms by the research community all over the world in several research initiatives. This work intends to be a review of remarkable projects for vertical sounding with a world wide network and for oblique sounding for high latitude, mid latitude, and trans-equatorial latitude.

An XYZ micromanipulator for precise positioning applications

A three-degrees-of-freedom (3-DOF) monolithic compliant parallel micromanipulator with bridge-type displacement amplifier is presented in this paper. The research aims are to design a monolithic mechanism with capability of working in three translational axes and having a high resonant frequency. As a result of being precise in rotation, circular flexure hinges are adopted in the structure of the proposed mechanism and its corresponding mathematical modeling is investigated. A finite element analysis (FEA) model is developed to perform analysis and predict the behaviour of the proposed mechanism and the utilized amplifier, and thus establish the computational Jacobian, workspace and amplification ratio. The stress-strain relationship of the proposed mechanism is investigated by applying safety factor and the results are presented. Finally, an experimental study is conducted to evaluate the dynamic and tracking performances of the proposed flexure-based spatial mechanism. A feedback Proportional-Integral (PI) control methodology is implemented to enhance the mechanism positioning performance and eliminate hysteresis effect inherent in piezoelectric actuators. Based on the designed parameters, the proposed manipulator can have a large workspace, high band-width frequency, and fine tracking resolution along each working axes.

Design and Optimization of Dual-Band Energy-Efficient OOK UWB Transmitter Via PSO Algorithm

A CMOS ON–OFF-keying 3–10.6-GHz transmitter with low power consumption and low complexity used to Impulse Radio Ultra-Wide Band (IR-UWB) communication system is presented in this work. This architecture is designed and optimized via particle swarm optimization (PSO) algorithm. The IR-UWB transmitter is adapted to generate a high bandwidth frequency and it has a band switching capability. It consists of a switching inductance–capacitance voltage-controlled oscillator (LC_VCO), a pulse generator circuit, an injection-locked frequency divider (ILFD) circuit, a buffer and an antenna. The VCO is switched ON/OFF by the pulse signal produced by a generator circuit which is realized through synchronizing the received data by a clock signal. The used technique for transmitting a discontinuous signal is based on a complementary switch-mode ON–OFF LC_VCO, whose main advantage is to reduce power consumption. In this work, a best agreement between the results of the optimization technique and those of the simulation is obtained. The simulated results illustrate a signal of pulse width of 2.5 ns and a pulse repetition rate (PRR) of 200 MHz. The output spectra are centered at 4-GHz and 8-GHz frequencies with 1,332-MHz and 1,350-MHz bandwidths, respectively. The peak-to-peak amplitude of a UWB signal output is 154[Formula: see text]mV. The IR-UWB transmitter power consumption is 11.4[Formula: see text]mW which corresponds to the consumption energy of 28.5 pJ/pulse @ 200[Formula: see text]MHz. The power spectral densities (PSDs) of the output signals of both circuits viz. ON–OFF LC_VCO and ILFD are less than [Formula: see text][Formula: see text]dBm/MHz, which agreed well with the Federal Communication Commission (FCC) regulation. The transmitter design is well implemented using a TSMC 0.18-[Formula: see text]m CMOS process technology in an Advanced Design System (ADS).

Construction principle of NES shock absorber and its application in frame structure

PurposeThe purpose of this paper is to describe the structure of nonlinear dampers and the dynamic equations, and nonlinear realization principles and optimize the parameters of nonlinear dampers. Using the finite element method to analyze the seismic performance of the frame structure with shock absorber.Design/methodology/approachThe nonlinear shock absorber was installed in a six-storey reinforced concrete frame structure to study its seismic performance. The main structure was designed according to the eight degree seismic fortification intensity, and the time history dynamic analysis was carried out by Abaqus finite element software. EL-Centro, Taft and Wenchuan seismic record were selected to analyze the seismic response of the structure under different magnitudes and different acceleration peaks.FindingsThrough the principle study and parameter analysis of the nonlinear shock absorber, combined with the finite element simulation results, the shock absorption performance and shock absorption effect of the nonlinear energy sink (NES) nonlinear shock absorber are given as follows: first, the damping of the NES shock absorber is satisfied, and the linear spring stiffness and nonlinear stiffness of the shock absorber are based on the relationship k1=kn×kl2, so that the spring design length is fixed, and the linear stiffness of the shock absorber can be obtained. The nonlinear shock absorber has the characteristics of high rigidity and frequency bandwidth, so that the frequency is infinitely close to the frequency of the main structure, and when the mass of the shock absorber satisfies between 0.056 and 1, a good shock absorption effect can be obtained, and the reinforced concrete with the shock absorber is obtained. The frame structure can effectively reduce the seismic response, increase the natural vibration period of the structure and reduce the damage loss of the structure. Second, the spacer and each additional shock absorber have a small difference in shock absorption effect. After the shock absorber parameters are accurately calculated, the number of installations does not affect the shock absorption effect of the structure. Therefore, the shock absorber is properly constructed and accurately calculated. Parameters can reduce costs.Originality/valueNew shock absorbers reduce earthquake-induced damage to buildings.

How Does Spectrum Affect Mobile Network Deployments? Empirical Analysis Using Crowdsourced Big Data

Despite the growing trend towards the use of big data methodologies, there is still limited application of such techniques to understand how spectrum is used in mobile networks. In this paper we analyse how low (<; 1 GHz) and high (>1 GHz) frequency spectrum is used in 4G networks in urban areas, in relation to eNodeB density, available bandwidth, Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ). We present a method to analyse the strategies used by Mobile Network Operators (MNOs) to deal with traffic congestion, and the degree to which they must densify their networks depending on their spectrum portfolio. Using crowdsourced data from 2017 from a popular mobile app, we apply this method to Greater London. We find that the fraction of sites that fully use all available bands to the MNO range from 2% to 20%. Additionally, MNOs with large bandwidth use 42% fewer sites on average in dense urban environments. This difference decreases in suburban areas to 23% fewer sites. The lowest frequencies in each eNodeB tend to exhibit lower RSRP values, as they are often used to serve cell-edge users. These frequencies also show lower RSRQ values because of higher interference caused by neighbouring cells. Similarly, large (high frequency) bandwidth improves RSRQ as it allows for fewer users per MHz, which reduces interference and enables larger cell sizes. We conclude that in dense urban environments, the available bandwidth, rather than propagation properties, determines the preferred band for network deployment by MNOs.

Wideband HF signals dispersion distortion compensator based on digital filter banks. Theory and approbation

Wideband HF signals dispersion distortion compensator based on digital filter banks. Theory and approbation