Search

A dual-band wireless power transfer (WPT) system is proposed to satisfy multiple distinct-band WPT demands. A power amplifier combined with a dual-band output matching coil, which is relatively compact, is adopted to enable asynchronous two-band power transfer for multiple single-band receivers (RXs). The measurement results revealed that the efficiency reached 71% for both 6.78 and 13.56 MHz when the transmitter (TX) coil and RX coil were in alignment. However, the efficiency of a dual-band WPT system decreases when the spacing between the TX coil and RX coil deviates from its optimal distance. To address this concern, boost converters were used in the RX ends to achieve higher efficiency under coil misalignments. Efficiency improvement of 14% was obtained when the deviation of the RX coil from the alignment center of the TX coil was 5 cm.

Wireless power transfer (WPT) techniques can provide safe and more convenient methods for charging electric scooter than the conventional method of wired charging. However, there is a specific zone of the charging platform for high-efficiency power charging. If the RX is not within the zone or misaligns from this zone, the transfer efficiency will deteriorate. Therefore, we propose a repeater array architecture to improve the coupling between TX and RX and increase the transfer efficiency. The simulation result show that the efficiency can reach 74.8% with a larger distance between TX and RX of 20 cm.

In this paper, T stub is adopted in the microstrip lines of the high-speed packaging to reduce the crosstalk. The impedance matching is also improved by using the enhanced core via with optimized surrounding ground vias. The simulation results show the lower far-end crosstalk and better impedance matching design are achieved. The signal integrity of the high-speed packaging has been improved and verified by the eye-diagram performance in the experiments.

In recent years, wireless charging has become a trend because it is convenient and safe. However, its efficiency can deteriorate when the distance between coils or the load varies. In this paper, an automatic $\pi$ - impedance matching method is proposed to obtain higher efficiency under dynamic-coupling or varied-load condition. The simulation results show that the efficiency can remain higher than 85% in varying transfer distances when coupling coefficient is over 0.3. For varied-load, the efficiency is higher than 80% when the load is over 20 ohm and reach around 88% as the load increases at the 6.78-MHz operating frequency.

Near-field dual-band wireless power transfer (WPT) systems can be compatible with distinct operating bands. Several systems are available with different architectures, such as multi-coil module or repeater-based coil module. However, their efficiencies become smaller when the coupling among coils change. In this work a dual-band WPT system with efficiency-tracking circuits-boost converters is proposed to obtain higher efficiency under dynamic-coupling applications. The simulation results show that the efficiency can be increased by 5-25% at 6.78 MHz and 13.56 MHz when the receiver coils are deviated from the optimal positions.

Dual-band coil modules facilitate efficient access to distinct-band, high-power, or rapid-charging wireless power transfer (WPT) systems. However, they do not function efficiently when the frequency ratio between two operating frequencies is large. To overcome this problem, we propose enhanced dual-band coil modules that adopt repeaters in the WPT system. We present a circuit-based analysis of repeaters in various dual-band coil modules compared with those in a single-band WPT system. The analytical results provide a design methodology applicable to diverse types of dual-band coil modules with a repeater in the WPT system. Our experimental results are consistent with the circuit-based analysis: coil power transfer efficiencies of 55% at 200 kHz and 74% at 6.78 MHz were obtained concurrently in the dual-band WPT system with a dual-band repeater. This paper reduced the application constraint of dual-band coil modules and facilitated the realization and application of multiband WPT systems.

A $1 \times 4$ antenna array with wideband and high gain is proposed for 60-GHz applications. The operating bandwidth is from 57 to 66 GHz. A superstrate above and an electromagnetic bandgap reflector below the array structure increase peak gain and decrease backward radiation, respectively. This paper elaborates the design guidelines. The slot stubs are designed appropriately to increase the bandwidth of square-slot antenna and maintain the radiation pattern. The simulated and measured impedance bandwidth ( $\vert S_{11}\vert \le -10$ dB) are 28.8% (52.6–69.9 GHz) and 23.2% (52.6–66.5 GHz), respectively. The peak antenna gain ranging from 57 to 66 GHz is simulated to be 14.2–12.4 dBi, while the measured peak gain at 57, 60, 63, and 66 GHz are 13.6, 13.4, 12.6, and 11.3 dBi, respectively. The above results can satisfy requirement of many commercial applications.

The Maier–Meier theory and Vuks theory were used to obtain the dielectric anisotropy and birefringence of the 4-cyano-4-pentylbiphenyl (5CB) liquid crystal system for a benchmark. The molecular dynamics (MD) simulation, coarse-grained molecular dynamics (CGMD) simulation, and the density functional theory (DFT) calculation were used to get the required parameters of the Maier–Meier theory and Vuks theory. The molecular density obtained by the MD simulation is about 1.05 g/cm3, which is very close to the available experimental value of 1.008 g/cm3. In the CGMD simulation, the order parameter is about 0.44 for the 5CB conformation at the temperature that the transformation from the nematic to disorder arrangement occurs. The polarizability (α), polarizability anisotropy (Δα), and dipole moment (μ) of a 5CB molecule were obtained by the DFT calculation with the functional of B3LYP/6-31+G(2d,p). With these parameters, the birefringence of 5CB by the Vuks theory is very close to the experimental value with the...

The most stable structure of the thinnest tungsten (W) nanowire with the radius of 1.9 A was predicted by the simulated annealing basin-hopping method (SABH) with the tight-binding (TB) potential and the penalty algorithm. At this small scale, the predicted tungsten nanowire is helical instead of in the BCC arrangement found in bulk tungsten material. The density functional theory (DFT) calculation on the uniaxial tensile simulation was carried out to obtain the stress–strain profile of the thinnest tungsten nanowire. From the stress–strain curve, the Young's modulus is about 7.3% lower than that of bulk W, and the yielding stress is about 31 times higher than that of bulk W. The adsorption energy variations of an O2 molecule on the top site of W atom at strain of 0 and 0.043 were used to explore the axial strain effect on the electronic properties of the thinnest W nanowire within the elastic region. Because the d-band center of the thinnest W nanowire at the strain of 0.043 becomes slightly closer to the Fermi level than that at strain of 0, the W atom of strained W nanowire becomes more reactive, resulting in the higher adsorption energy and the shorter W–O bond length. The density functional theory molecular dynamics (DFT-MD) simulation for the temperature elevation process was carried out for understanding the thermal stability of the thinnest W nanowire. The result shows the considerable deformation of local structure occurs at the temperature higher than 860 K, indicating the thinnest W nanowire can be safely used at the temperature lower than 860 K.

Two CO oxidation reactions (CO + O2 → CO2 + O and CO + O → CO2) were considered in the Eley-Rideal (ER) reaction mechanism. These oxidation processes on the W(111) surface and the W helical nanowire were investigated by the density functional theory (DFT) calculation. The stable adsorption sites of O2 and O as well as their adsorption energies were obtained first. In order to understand the catalytic properties of the W helical nanowire, the Fukui function and local density of state (LDOS) profiles were determined. The nudged elastic band (NEB) method was applied to locate transition states and minimum energy pathways (MEPs) of CO oxidation processes on the W helical nanowire and on the W(111) surface. In this study, we have demonstrated that the catalytic ability of the W helical nanowire is superior to that of the W(111) surface for CO oxidation.

Wireless Power Transfer (WPT) technology can provide convenience and improve some wired power issues so that it is gradually applied to the our daily life. Metamaterial is one of solutions to increase WPT efficiency. In this work the multi-layer metamaterial slab is proposed to improve the performance of conventional metamaterial that is applied at a WPT system. The simulation results show the efficiency of a WPT coil module can be increased by adopting multi-layer metamaterial slab when the effective separation distance of a WPT coil module remains unchanged.

A multi-band wireless power transfer (WPT) will be one of the important WPT research trends in the future. This work presents a single-coil dual-band WPT coil module as an example in the multi-band WPT applications. It can transfer more power than a single-band WPT can do within the electromagnetic field constraints. Moreover, one of its channels can be used to provide a higher data communication rate than that of a single-band WPT. Different from a multi-coil multi-band WPT, no unwanted cross coupling exists in this dual-band coil module because it uses only one coil for power coupling. An analytical process of the dual-band coil design guideline is presented. We can improve coil power transfer efficiency in the weakly coupling region and avoid frequency splitting in the strongly coupling region by selecting appropriate coil parameters as presented. The experimental results are in good agreement with the coil module analysis. Therefore, a flexible dual-band WPT coil module is obtained in this work.

The most stable structures of three ultrathin molybdenum (Mo) nanowires were predicted by the simulated annealing basin-hopping method (SABH) with the penalty algorithm. The predicted structures of Mo nanowires indicate that, at this small scale, they do not possess the BCC configuration found in bulk Mo material. Mechanical properties including the Young's modulus, yielding stress, and strength of these wires were determined by a tensile test after the analysis of the stress–strain profiles. In addition, in order to understand the feasibility of application of these Mo nanowires in nano-devices, their thermal stability was also investigated at room temperature (300 K) by MD simulation.

The model for a compact bandpass filter which has multi-section structure and equivalent elements of package is proposed in this paper. With six vertical via-holes and three planar coupled lines, a multi-section coupled line is available. There are wide upper stopband and multi transmission zeros in the proposed design. This device is implemented in a low temperature co-fired ceramic substrate with thin thickness and shows good rejection with 20 dB rejection level that up to 4.4 × f 0 . The design also performs co-simulation with SiP model and shielding metal around the device to evaluate the total performance. The EVM measurement in system is available as well. The simulation and measurement results are in good agreement results.

A novel broadband and high gain aperture-coupled microstrip patch array antenna is developed for AiP solutions. The compact size of the whole AiP is only 10×8.5 mm2. The array antenna structure consists of parallel and series feed networks. A 16-element aperture microstrip coupled patch array antenna achieves over 15% of the operating bandwidth from 57 to 70 GHz which covers global unlicensed band at around 60 GHz. The proposed antenna peak gain can achieve 15 dBi at 65 GHz and can be utilized for two basic AiP solutions, including vertical and horizontal configurations.

Applying metamaterial mechanism into the wireless power transfer (WPT) system is one of potential methods for improving power transfer efficiency (PTE). Different from the conventional metamaterial slab with single negative permeability (SNP), the WPT with hybrid negative permeability (HNP) slab has higher PTE. In this paper, we investigate the parameters of HNP slab at different position between WPT coils. The simulation results show that the optimal parameters of HNP for high PTE is dependent on the metamaterial slab position. By adopting an appropriate HNP slab, the higher PTE can be obtained at required arrangement of WPT coil module with the metamaterial slab.

This paper presents a novel approach to construct a multiple-input multiple-output (MIMO) antenna in a small package based on integrated passive device (IPD) manufacturing technology. Such an IPD utilizes a thin-film glass substrate that yields a low loss performance for RF components. A thin film process with limited layers available and size considerations in IPD manufacturing pose major challenges in antenna design, especially for multiple antennas. This thin-film process results in a high cavity quality factor (Q) causing a narrowband in the conventional patch antenna. To overcome this problem, this paper develops antenna elements that incorporate a T-shaped coupling fed driven strip and a loop structure. The gap between the driven strip and the loop structure functions as an internal tuning circuit, thus contributing to a lower overall Q and antenna miniaturization. The size of the proposed antenna element is only 1.8 × 0.65 mm2 (0.031 λ0×0.011 λ0) in the IPD size of 4 × 4 mm2 (0.068 λ0×0.068 λ0). The experimental results indicate that the antenna achieves a gain of 1.4 dBi and a radiation efficiency of 60% over the IEEE 802.11a band (5.15-5.825 GHz). In addition, the multiple antenna elements are arranged to construct a MIMO system. Furthermore, a good isolation is achieved using a space of only 0.3 mm (0.005 λ) spacing between two antennas, resulting in a compact design and small package (4 × 4 × 0.25 mm3). The parameters are also investigated in detail, with the experimental results correlating well with the simulation results.

Energetically favorable configurations of silica nanowires with helical and non-helical structures and diameters ranging from 0.4 to 1.5 nm were obtained by using the simulated annealing basing-hopping (SABH) method with penalty function in our previous work. Those nanowires include five non-helical (2MR, 2MR-2O, 3MR-3O, 4MR-4O, and 5MR-5O) and three helical structures (4MR-3f, 4MR-4f, and 4MR-5f). In this study, their mechanical properties and structural characteristics were carried out by molecular dynamics simulation, specifically the temperature and diameter effect on the tensile strength, yielding strain, and Young’s modulus. Results show that diameter significantly affects Young’s modulus and yielding stress, whereas the temperature mainly influences yielding strain and yielding stress. The elastic deformation allows the variation of θO–Si–O to be about >16°. For comparison and insight, the mechanical property and deformation behaviors in the tensile loading are compared to those in the compression loading. Buckle deformation was observed on both helical and non-helical nanowires under the compression process, demonstrating that the nanowires exhibit a higher yielding strain and Young’s modulus in the compression loading than in the tensile loading. In both the tensile and compression tests, the helical angle structures of silica nanowires lower the yielding strain and only slightly affect the yielding stress and Young’s modulus.

A new technique to achieve both good isolation and dual band-notched functions for ultrawideband (UWB) multiple-input–multiple-output (MIMO) antennas was developed. The proposed antenna consists of the radiation patch connected through a via with the strip placed beneath the patch. The strip not only provides another coupling path, but also serves as the impedance transformer, resulting in good isolation ( $S_{21} dB) and dual band rejection at WiMAX (3.4–3.7 GHz) and WLAN (5.15–5.35 and 5.725–5.825 GHz) over the UWB system operation (3.1–10.6 GHz). Without decoupling element or resonator, which is often placed between the antennas to acquire good isolation or band rejection, the proposed UWB MIMO antenna requires an individual antenna element size of only 11.2 $\,\times\,$ 12 mm $^{2}\ (0.12 \lambda_{0}\times 0.11 \lambda_{0})$ and overall MIMO antenna size of 30 $\,\times\,$ 40 mm $^{2}\ (0.31 \lambda_{0}\times 0.41\lambda_{0})$ . The edge-to-edge separation between antennas is $0.052\lambda_{0}$ , and separation between feeds is $0.175 \lambda_{0}$ at 3.1 GHz. Detailed investigations of the parameters were performed, and the experimental results agree closely with the simulation results, demonstrating the feasibility of the proposed method.

The structural and electronic properties of small tungsten nanoclusters Wn (n = 2–16) were investigated by density functional theory (DFT) calculations. For the W nanocluster, the lowest-energy structures were first obtained by the basin-hopping method (BH) with the tight-binding many-body potential for a bulk tungsten material. These structures were further optimized by DFT calculations in order to find better parameters of the tight-binding (TB) and Finnis–Sinclair (FS) potential appropriate for W nanoclusters. The values of binding energy and second-order energy difference reveal that the structure W11 has a higher stability than those of other sizes. The vertical ionization potential (VIP), adiabatic electron affinity (AEA) and HOMO–LUMO gap are also discussed for W nanoclusters of different sizes. In addition, large size nanoclusters Wn (n = 30–120) are obtained by the BH method, and a comparison of the structural properties determined by TB and FS potentials are represented with Honeycutt–Andersen index analysis.

The mechanical properties of polyglycolic acid (PGA) of different water weight fractions (1.7%, 2.9%, and 5%) were investigated by molecular dynamics (MD) simulation through a tensile test. The variation in the degree of crystallinity with water content was also investigated using XRD profiles. The Young's modulus, mechanical strength, and fracture mechanism of all PGA–water systems were drawn from the corresponding stress–strain profiles. Furthermore, water diffusion behavior within the PGA matrix both before and after the tension test was also studied. The water diffusion coefficients were derived from the mean square displacements of all water molecules within the PGA matrix.

Channel prediction can provide up-to-date information about the state of a channel in OFDM systems at the expense of increasing the complexity of wireless systems. Therefore, this paper proposes a novel approach for optimizing the shape and intervals between samples in two-dimensions (2-D) for an orthogonal frequency-division multiplexing (OFDM) system to reduce the complexity of predicting the channel frequency response (CFR). Furthermore, the proposed prediction scheme has the flexibility to integrate with an adaptive algorithm which does not require any statistical prior knowledge and is able to track nonstationary channel statistics. The number of multipliers that are required to predict the CFR is reduced by predicting the CFRs at particular subcarriers and incorporating interpolation methods. This paper also deals with the proposal of a 2-D curve fitting (CF) interpolator to be used for predicting the CFR that allow improving the accuracy of the CFR prediction. Simulation and analysis results demonstrate that the 2-D CF interpolator combined with the proposed scheme has lower complexity than the other approaches to predicting CFR, without compromising the mean square error (MSE) or bit error ratio, even in a noisy and fast-fading channel environment.

The studies of silica nanoclusters are of substantial interest for large potential in applications as diverse as photonics/optics, microelectronics and catalysis. In this study, we used the basing-hopping method with Buckingham potential to get the stable structures of silica nanoclusters ((SiO2)(n) = 1-13). The global minimum geometry of silica nanoclusters were determined by density functional theory calculation. We investigated the energy gap, binding energy and second order energy difference of nanoclusters to determine their structural stability with different sizes. We also calculate the second-order energy difference, binding energy to determine the magic number.

The mechanical properties of Ni-Ta crystallizationand binary bulk metallic glasses (BMG) were investigated for this study at the nanoscale. First, the Ta9Ni3 crystals are formed by space group, and structures with different ratios (Ta1Ni1, BTa8Ni4, BTa9Ni3, BTa7Ni5) were put into unit cell randomly. The optimizations of BMG structures are performed by Density functional theory (DFT) calculation to find the stable amorphous structures and corresponding energy. The FMM is utilized to obtain the suitable parameters of tight-binding potential bystable amorphous structures and corresponding energies. Finally, we employ molecular dynamics (MD) simulation to study mechanical properties of Ni/Ta crystallization and BMG, such as atomistic stress-strain, plastic and elastic deformation, and elastic modulus.

The adsorption and dissociation properties of carbon monoxide (CO) molecule on tungsten W(n) (n = 10-15) nanoparticles have been investigated by density-functional theory (DFT) calculations. The lowest-energy structures for W(n) (n = 10-15) nanoparticles are found by the basin-hopping method and big-bang method with the modified tight-binding many-body potential. We calculated the corresponding adsorption energies, C-O bond lengths and dissociation barriers for adsorption of CO on nanoparticles. The electronic properties of CO on nanoparticles are studied by the analysis of density of state and charge density. The characteristic of CO on W(n) nanoparticles are also compared with that of W bulk.