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This article presents a 320 $\times $ 240 indirect time-of-flight (iToF) CMOS image sensor (CIS) with on-chip motion artifact suppression and background light cancelling (BGLC). The proposed iToF CIS uses a backside-illuminated trident pinned photodiode (PPD) that assists charge transfer with a built-in lateral electric field for enhanced depth accuracy. To overcome the limitation of the conventional iToF CIS that exhibits motion artifact, we propose a pseudo-four-tap (P4-tap) demodulation method with alternate phase driving using a conventional two-tap pixel structure with a high fill factor of over 43%. In addition, by combining the advantages of both the P4-tap and conventional two-tap demodulation schemes, we propose hybrid depth imaging with reduced motion artifact for moving objects, while providing high-depth precision for the static background. For outdoor mobile applications of the iToF CIS, we integrated on-chip BGLC circuits to eliminate the BGL-induced depth error. A prototype chip is fabricated using a 90-nm backside illumination (BSI) CIS process. The BSI trident PPD enabled a low depth error of under 0.54% over the range of 0.75–4 m, with a modulation frequency of 100 MHz. Motion artifact was suppressed at 60 frames/s of hybrid depth imaging owing to the proposed P4-tap scheme. With the on-chip BGLC circuit, the experimental results demonstrate a 0.55% depth error at a 1-m distance, even under 120-klx BGL illumination. [ABSTRACT FROM AUTHOR]

Acoustic-resolution photoacoustic microscopy (AR-PAM) is a promising technology for vascular or tumor-targeted molecular imaging. Unique advantages of AR-PM are its non-invasive, non-ionizing real-time, and deeper imaging depth. AR-PAM typically uses an ultrasound transducer with a high acoustic numerical aperture (NA) to enable deeper imaging depth. While high NA achieves good lateral resolution in the focal plane but significantly degrades the lateral resolution in the out-of-focus region. Synthetic aperture focusing technique (SAFT) has been introduced to overcome this out-of-focus degradation by synthesizing the correlated signals. Several 2-D SAFTs have been also reported to improve degraded resolution in all directions. However, the resolution enhancement of the previously reported 2-D SAFTs are suboptimal and are not equivalent to the 1-D SAFT performance under an ideal condition with the sample orientation perpendicular to the synthetic aperture direction. In this paper, we present a new 2-D SAFT called 2-D directional SAFT that improves the lateral resolution significantly and we compare our results against 1-D SAFT under ideal condition. We applied this algorithm to phantom and in vivo images to show the improvement in image quality. We also implement this algorithm in a graphical processing unit to achieve high performance to show the practicality of implementing this new algorithm in a system. [ABSTRACT FROM AUTHOR]

The Mn–Bi nanoparticles were prepared by using laser ablation and arc-discharge method, respectively. The arc-evaporated Mn–Bi nanoparticles exhibit ideal spherical shape with size in the range of several tens of nanometers to several hundreds of nanometers, whereas the laser-ablated Mn–Bi nanoparticles exhibit an irregular shape with smaller particle size. The Bi content in the arc-evaporated Mn–Bi nanoparticles was significantly enhanced compared to that of the Mn–Bi master alloys because of the higher vapor pressure of Bi than that of Mn in the melt. The Mn content in the arc-evaporated Mn–Bi nanoparticles increases with increasing Mn content in the master alloys. However, the Bi and Mn contents in the laser-ablated nanoparticles deviate little from that of the master alloys because of the highly localized molten pool of MnBi over the surface of the master alloys and the higher temperature reached using laser beams. The fraction of the low-temperature phase MnBi in the nanoparticles prepared by both methods increases with increasing annealing temperature and time. The laser ablation method is more effective in controlling the composition of the products. The coercivities of the arc-evaporated and laser-ablated Mn–Bi nanoparticles after annealing reached up to 0.65 and 0.8 T, respectively. The saturation magnetization of the annealed laser-ablated Mn–Bi nanoparticles reaches up to 51.6 Am2/kg. [ABSTRACT FROM AUTHOR]

We report a simple wireless power charging (WPC) antenna system (50 mm \times40 mm \times0.1 mm) for use in simulating power transfer efficiency ( \eta ) with and without ferrite and a metallic object (battery case), thereby identifying suitable magnetic parameters and ferrite sheet thickness. The simulation results suggest that magnetic loss tangent (tan ) and permeability ( \mu ' ) need to be less than 0.05 and higher than 125 at 13.56 MHz, respectively, to achieve at least 75% of the transfer efficiency ( \eta \mathrm {max} ) of the WPC antenna without ferrite and the metallic object. Accordingly, we have fabricated NixZn0.85–xCu0.15Fe2O4 (x = 0.32 – 0.38) spinel ferrites using a one-step sintering process and obtained relatively high \mu ' of 169 and low tan \delta \mu of 0.1 with a nickel (Ni) concentration of 0.38. This magnetic loss is still too high to achieve 75% of the \eta \mathrm {max} value. In order to further reduce the magnetic loss, a two-step sintering process was used. The two-step sintered Ni0.38Zn0.47Cu0.15Fe2O4 shows $\mu '$ of 132 and a tan \delta \mu of 0.03 at 13.56 MHz, respectively. Therefore, this ferrite meets criteria identified by the transfer efficiency simulation and is a good candidate for 13.56-MHz wireless power transfer charging antenna system. In addition, our designed WPC system is capable of evaluating other magnetic materials that are suitable for WPC antenna applications. [ABSTRACT FROM AUTHOR]

We have calculated the electronic structures of FePt and Fe0.9375Mn0.0625Pt using first principle calculations based on density functional theory within the local-spin-density approximation (LSDA). The Curie temperature ( Tc) was calculated by a simple model based on the mean field approximation. A supercell structure, containing eight unit cells, was used to calculate the density of states. The saturation magnetization ( Ms) and magnetocrystalline anisotropy constant ( K ) at 0 K, and T_{c} for Fe0.9375Mn0.0625Pt were calculated to be 942 emu/cm3, 8.24 \times 10^{6} J/ \textm^3 , and 590 K, respectively. The temperature-dependent M(T) and K(T) of Fe0.9375Mn0.0625Pt were calculated using the Brillouin function and Callen–Callen experimental relation, respectively, to obtain an M_{s} and a K of 822 emu/cm3 and 6.29 \times 10^6 J/ \textm^3 at 300 K, respectively. These values meet the required Ms and $K$ of 800 emu/cm3 and 5.00 \times 10^{6} J/ \text{m}^{3} for achieving 4 Tb/in2 heat-assisted magnetic recording media (HAMR). [ABSTRACT FROM PUBLISHER]

Miniature low-profile multiband ferrite antennas were designed with various BaCo1.4Zn0.6Fe16O27 hexaferrite loading configurations and fabricated for telematics applications. Experimental permeability ( \mu ^\prime ) of 2.0, permittivity ( \varepsilon ^\prime ) of 7.3, magnetic loss tangent (tan \delta \mu ) of 0.035, and dielectric loss tangent (tan \delta \varepsilon ) of 0.005 at 1 GHz were used for antenna performance simulations. It is observed that a hollow rectangular ferrite substrate loading shows simulated maximum ripple levels ( \Delta = E\theta \\max -E\theta \\min ) of 2.2, 3.0, and 1.9 dB at the first ( f1 ), second ( f2 ), and third ( f3 ) resonant frequencies, respectively, implying wider coverage than other loading configurations. Miniaturization factor is greater than that of air-core antenna, and the impedance matching and bandwidth are improved with the ferrite loading. Higher gain of the ferrite-loaded antenna than the air-core antenna was observed at f2 and f3 , while the gain at f1 remains almost the same. Moreover, the vertical component E\theta is greater than the horizontal component E\phi , showing the vertically polarized operation of the antenna. Based on the measured and simulated results, it is concluded that the BaCo1.4Zn0.6Fe16O27 substrate loading allows antenna miniaturization with enhanced antenna performance. [ABSTRACT FROM PUBLISHER]

Optimization of magnetic read widths (MRWs) and reader positions in two-dimensional magnetic recording (TDMR) is explored in order to maximize an areal density (AD) gain over shingled magnetic recording (SMR). The optimization is based on micromagnetic waveforms from 511-bit maximal-length pseudorandom binary sequence (PRBS) patterns. The identical MRWs for two readers are initially considered and the best reader offset is found in order to achieve the largest AD gain. Given the best reader offset, the MRWs for the two readers are changed to further enhance the AD gain. A software channel is utilized to identify the major contribution of the TDMR AD gain. [ABSTRACT FROM AUTHOR]

Drive-level pattern-dependent bit error rate (BER) and signal-to-noise ratio (SNR) degradation during thermal decay were studied. A 511 bit pseudorandom binary sequence was used to help reveal the fundamental relationship between degradation trends of SNR and BER. Degradation profiles of both SNR and BER within specific patterns were plotted and analyzed. In the short-term thermal decay, SNR mostly decayed at the nontransition part, while BER mostly decayed at the transition part. It was found that transition BER degradation was caused by the degradation of nontransition SNR, while nontransition bits hardly have any error until nontransition SNR degradation reached certain levels. It was difficult to observe nontransition BER degradation in thermal stability experiments, which were normally limited by time. Simulation is necessary to assist the prediction of thermal decay performance. [ABSTRACT FROM AUTHOR]

Mn54Al46C2.44 alloy as new permanent magnetic materials was produced by induction melting, and its powders were produced by low energy ball milling. The milled powders were annealed to study the effect on their phase transformation and magnetic properties. The powder undergoes massive phase transformation at an annealing temperature of 450 °C, and reaches the maximum saturation magnetization ( \sigma s) when annealed at 480 °C for 5 min, while its intrinsic coercivity ( H\mathrm {ci}) continually increases with the temperature. The initial increment of the H\mathrm {ci} is due to the phase transformation from paramagnetic \varepsilon -phase to ferromagnetic \tau -phase and remaining \varepsilon -phase and formation of secondary phases, such as nonmagnetic - and \beta -phases, that acts as pinning points for the domain walls. The next one is caused by the increasing percentage of the secondary phases that decreases \sigma s . Based on the delta M analysis, it can be verified that the increased H\mathrm {ci} with increasing secondary phases when annealed at temperatures above 480 °C is due to the decreasing magnetization. [ABSTRACT FROM AUTHOR]

Magnetic recording at the highest areal density on conventional granular recording media uses $\sim 10$ grains to carry each bit of customer data. Efforts to reduce this number have focused on improving the resolution of the writing and reading processes and, in particular, on improving uniformity of the recording medium and on incorporating knowledge of the recording medium statistics into the detection process. This paper considers the extreme case of data detection on a perfect hexagonal array of grains. This paper looks at two aspects: 1) the estimation of the angle and positioning of the array with respect to the bit-steam and 2) the use of that information to assist data detection. At aggressive densities with very few grains per bit (GPB), the estimation proceeds well and the extra information is helpful in detection. With more GPB, the gains become small. [ABSTRACT FROM AUTHOR]

In this paper, we present a technique of noise analysis for perpendicular and shingled magnetic recording that is variance centric, i.e., with analysis focused on noise power. Measured noise from a home track viewpoint is decomposed into electronic noise, transition noise, nontransition noise, and inter-track interference components. The separation of media noise into transition and nontransition noise components is accomplished by a variance deconvolution technique. Experimental noise analysis is shown for cases of track squeeze, adjacent track erasure, and read head offset. Potential capacity gains are also assessed for the case of electronic noise improvement. [ABSTRACT FROM PUBLISHER]

In this paper, a general energy expression is developed for a cluster of multilayer exchange spring media grains. We expand the rotation of the magnetization vectors to second order in elements of an exponential unitary transformation. The first and second derivatives of the energy are determined and a damped optimization procedure is used to efficiently locate minima and transition states on the potential energy surface. In this method, the interaction of neighboring grains is taken into account and thus the effect of inter-granular exchange on the energy barrier is explicitly taken into consideration. Thus, cluster formation is seen as coherent switching of a group of grains and can be studied as a function of anisotropy and exchange distributions in the media. The lowest energy barrier for a grain or cluster is then used to construct a rate constant. We then determine rate constants for an ensemble of interacting grains from which M-H loops and magnetization decay are simulated as a function of an applied field. Both kinetic Monte Carlo and direct integration of the rate equations are used to study the kinetics of these systems. We find that thermal decay rates have better correlation with energy barriers than with nucleation fields. [ABSTRACT FROM PUBLISHER]

We present the state-of-the-art system level evaluation of the IEEE 802.22-2011 standard using a highly detailed simulator implementation in NS-2. In the evaluation our attention is focused on the effect of spatiotemporal wireless microphone (WM) activity on the performance of the IEEE 802.22-2011 network, while considering novel spectrum sensing strategies and multimedia traffic with different prioritization in IEEE 802.22-2011. Our general finding is that the IEEE 802.22-2011 standard deals well with WMs and prioritization of simultaneous multimedia traffic using different QoS profiles, while some surprising conclusions follow. [ABSTRACT FROM AUTHOR]

We demonstrated the size reduction of axial-mode helical antenna based on Co2Z hexaferrite-glass composite. Axial-mode helical antenna was employed to provide reliable communication for unmanned aerial vehicle (UAV) applications. The conventional axial-mode helical antenna uses an air core or low dielectric material, resulting in large antenna size. To increase the miniaturization factor n=(\mur\varepsilonr)^0.5, a Co2Z hexaferrite-glass composite was used as an antenna core. The 3-dimensional finite element method (FEM) simulation was performed to design a hexaferrite helical antenna and confirm the axial-mode operation at 2.44 GHz with gain of 2.0 dBi. The designed hexaferrite helical antenna showed 82% of volume reduction and good impedance matching compared to the air-core antenna. The axial-mode hexaferrite antenna was fabricated based on the designed structure and characterized in an anechoic chamber. The maximum gain of 0.541 dBi was measured with the pitch angle of 10^\circ at 2.39 GHz. Also, a two-element axial-mode antenna array was designed based on the miniature hexaferrite antenna to further improve antenna gain. Maximum gain of 4.5 dBi at 2.43 GHz was simulated for the antenna array. Therefore, high gain and miniature antenna can be achieved with the combination of Co2Z hexaferrite-glass composite and antenna design technology. [ABSTRACT FROM AUTHOR]

We present an analytical model that enables the evaluation of opportunistic spectrum orthogonal frequency division multiple-access (OS-OFDMA) networks using metrics such as blocking probability or, most importantly, throughput. The core feature of the model, based on a discrete-time Markov chain, is the consideration of different channel and subchannel allocation strategies under different primary and secondary user types, traffic, and priority levels. The analytical model also assesses the impact of different spectrum sensing strategies on the throughput of OS-OFDMA network. In addition, we consider studies of cochannel interference. The analysis is applied to the IEEE 802.22 standard to evaluate the impact of the two-stage spectrum sensing strategy and the varying temporal activity of wireless microphones on the system throughput. In addition to the analytical model, we present a set of comprehensive simulation results using NS-2 related to the delay performance of the OS-OFDMA system considered. Our study suggests that OS-OFDMA with subchannel notching and channel bonding could provide almost ten times higher throughput compared with a design without these options when the activity and density of wireless microphones are very high. Furthermore, we confirm that OS-OFDMA implementation without subchannel notching, which is used in the IEEE 802.22, can support the real-time and non-real-time quality of service classes, provided that the temporal activity of wireless microphones is moderate (with sparse wireless microphone distribution, with light urban population density and short duty cycles). Finally, the two-stage spectrum sensing option improves the OS-OFDMA throughput, provided that the length of spectrum sensing at every stage is optimized using our model. [ABSTRACT FROM PUBLISHER]

The scaling effect of permalloy s-shaped element, a rectangular element with appendages, on operating fields, Hx and Hy, was investigated by micromagnetic computer simulations for and or or logic. The optimized combination of operating fields (Hx, Hy) was found to be (27.7 \pm 9.9, -16.7 \pm 8.8), (37.9 \pm 12.4, -25.9 \pm 6.0), and (42.2 \pm 8.8, -23.9 \pm 4.0) in kA/m for the 100, 50, and 30 nm long s-shaped elements, respectively. As the s-shaped element is scaled down, the allowable deviation from the optimized operating fields becomes smaller and optimized operating fields shift to higher field. [ABSTRACT FROM AUTHOR]

We have experimentally and analytically studied the writeability and recording characteristics of perpendicular magnetic recording media in which the anisotropy (Ku) of the granular oxides and the magnetization (Ms) and lateral exchange coupling (Aex) of the cap layer were varied. The analytical results are obtained with a 9-spin model, which consists of 3 grains with 3 layers each, representing dual oxide media with a capping layer. The 9-spin model estimates bit error rate (BER) using an error-pattern-correcting code (EPCC) based iterative channel model. The experimental results qualitatively agree well with the analytical results of the 9-spin model. High Ku gradient oxides and high Ms cap layer improve writeability and BER, whereas high Aex in the cap layer degrades switching field distribution and off-track capability. Media switching field and switching field distribution strongly depend on spatial distribution of the external field. Both experimental and analytical results indicate that an appropriate design of Ku graded media with an optimum cap layer can effectively reduce jitter and switching field distribution for given head fields, resulting in higher recording density. [ABSTRACT FROM AUTHOR]

An array of ferrite and air-core inductors was fabricated on silicon wafer to characterize inductor performance. The 1 \mu\m and 2.5 \mu\m thick ferrite films for the fabrication of inductors were prepared by dc magnetron sputtering. The inductance of the ferrite inductor increased with the thickness of ferrite film from 45.5 nH for 1 \mu\m thick ferrite to 50 nH for 2.5 \mu\m thick ferrite. The maximum Q-factor was obtained to be 59 at 2.87 MHz from 2.5 \mu\m thick ferrite inductor, which is higher than 49.3 at 2.26 MHz for 1 \mu\m thick ferrite inductor and 23.2 at 1.56 MHz for air-core inductor. Superimposed dc current of 1 \mu\m and 2.5 \mu\m thick ferrite inductors was estimated to be 2.5 A and 2.15 A, respectively, corresponding to a 5% drop in L at 10 MHz. In addition, the power efficiency of the buck dc-dc converter based on the studied ferrite inductors was calculated to be 91.7% for 2.5 \mu\m thick ferrite inductor and 90.1% for 1 \mu\m thick ferrite inductor at load current of 0.647 A. [ABSTRACT FROM AUTHOR]

A systematic investigation of the switching behavior and writeability characteristics of perpendicular magnetic oxide media was performed by varying the number of oxide layers as well as the anisotropy Ku gradient in multilayered oxides. The media switching behavior highly depends on the magnetic volume of laterally exchange-coupled cap layer as well as the vertical exchange coupling between oxide and cap layers. The media switching field is significantly reduced with incoherent switching mode. The media writeability is further enhanced by employing the multilayered oxides whose anisotropy values vary. Higher Ku graded oxide media exhibits improved resolution, sharper transition, and higher signal-to-noise ratio. An analytical 9-spin model is used to study the impact of anisotropy grading, intergranular and interlayer exchange coupling on writeability and noise performance. The 9-spin model is found to qualitatively agree with the experimental results. Both model and experiment indicate that optimal tuning of the media anisotropy and exchange to the head design is critical in attaining good recording performance. [ABSTRACT FROM AUTHOR]