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The objective of this paper is to propose a method for quantitatively estimating the breakdown voltage of double short vacuum gaps in series under the lightning impulse voltage. The study found a quantitative relationship between the breakdown voltage and the maximum electric field strength at the cathode. This relationship is validated by previous experimental works when the total gap distance is less than 20 mm. [ABSTRACT FROM AUTHOR]

A switchable bandstop filter (BSF) bank in 3-D heterogeneous integration is presented in this article for multiband applications. Compared with conventional filter banks, the proposed design features wide bandwidth, sharp skirts, compact size, and high integration. In the proposed BSF, double short-ended coupling lines are introduced to expand the operation bandwidth with sharp rejection. Moreover, to significantly reduce the size of the proposed BSFs, an in-house silicon micromachining process is developed to heterogeneously integrate two stacked BSFs with switches by through-silicon vias (TSVs). To experimentally validate the proposed configuration, a two-channel switchable BSF bank is designed, fabricated, and measured. The measured results show a tuning range of 7.95–12.3 GHz (43%), a maximum bandwidth of 30%, and a sharp stopband rejection of 50 dB. These results agree well with simulation. Moreover, the fabricated prototype is only 15 $\times 8\times $ 1 mm3, whereas a typical industrial counterpart is around $86\times 74\times18$ mm3, i.e., the size is significantly reduced to 1‱. To the best of the authors’ knowledge, this is the first demonstration of a wideband switchable sharp-rejection BSF chip fully integrated in the TSV process. [ABSTRACT FROM AUTHOR]

A 4 × 64 pixel 3-D CMOS imager based on time-offlight (TOF) has been developed and successfully tested. The measurement range is up to 8 m with resolution of 1 cm. The scene depth is determined by measurement of the travel time of reflected laser pulses by employing a fast on-chip synchronous shutter (maximum shutter speed 30 ns). The Multiple Double Short Time Integration (MDSI) algorithm enables suppression of the background illumination and correction for reflectance variations in the scene objects. The pixel size is 130 × 300 µm². The sensor chip has been realized in a 0.5-µm n-well standard CMOS process. [ABSTRACT FROM AUTHOR]

A class of balanced dual-band planar diplexer with frequency-contiguous channels for the differential mode and high common-mode rejection is presented. It exploits double-stub-loaded filtering cells with resistors connected at the symmetry plane of the overall diplexer. In this manner, a sharp-rejection dual-band operation for each diplexer channel with transmission zeroes (TZs) at both sides of the differential-mode dual passbands is obtained. In addition, broadened common-mode suppression and low common-mode in-band input power reflection can be realized. The theoretical foundations and design guidelines for the devised dual-band differential-mode diplexer are provided. Moreover, for practical-validation purposes, a microstrip prototype with imbricated 1.51-GHz/2.41-GHz and 1.92-GHz/2.85-GHz lower and upper dual-band channels is manufactured and tested. [ABSTRACT FROM AUTHOR]

Partial breakdown (PB) has been reported in breakdown of vacuum gaps in series but has not been fully understood. The objective of this article is to investigate the influence of PB on breakdown of vacuum gaps in series under lightening impulse voltages. Two commercial vacuum interrupters (VIs) of the same model were connected in series with various gap distance arrangements. Experimental results show that four breakdown types could be classified, i.e., repeatedly PB without final full breakdown of the series gaps (type I), two PBs before final full breakdown (type II), one PB before final full breakdown (type III), and no PB before final full breakdown (type IV). Breakdown voltage of the vacuum gaps in series decreases with the increasing difference between the two gaps and could be even lower than breakdown voltage of the larger gap alone. This is explained by analyzing the three stages of transients induced by a PB. A model was established to simulate transients induced by PB of the vacuum gaps in series. The simulated results could match the experimental results well. An evolution process from a PB to the four breakdown types was deduced. The influence of PB on insulation coordination and breakdown voltage of the vacuum gaps in series was analyzed according to the abovementioned analysis. [ABSTRACT FROM AUTHOR]

The objective of this article is to propose a novel prediction method of the breakdown (BD) probability for multiple vacuum gaps (VGs) in series considering their dielectric recovery under a lightning impulse voltage. Based on the experimental data of the BD probability for each single VG and the calculated voltage distribution of multiple VGs, the BD probability of multiple VGs in series could be calculated by the proposed prediction method. By dielectric tests under the lightning impulse voltage, we see that the calculated BD probability distributions fit well with the experimental results for double VGs and triple VGs in series. Under sphere–plane electrode VGs, the prediction error was approximately 15% in the whole range of BD probabilities. The errors of the 50% BD voltage were 11.4% and 12.9% for double VGs and triple VGs in series, respectively. Therefore, the reliability of this prediction method considering the dielectric recovery was validated. This prediction method could be used to estimate the dielectric strength of multibreak vacuum circuit breaker (VCB) and multiple floating shields inside high-voltage vacuum interrupters. [ABSTRACT FROM AUTHOR]

With the successful test of the first two pre-series magnets the US HL-LHC Accelerator Upgrade Project has started production of the MQXFA magnets to be used in Q1/Q3 inner triplet elements of the HL-LHC. This good start comes after the test of two prototypes with limited performance, and it demonstrates the importance of learning from past issues. Therefore, in this paper we want to share the most important lessons learned so far, focusing on those which may be more interesting for similar projects. We will also present the status of MQXFA fabrication in the US. [ABSTRACT FROM AUTHOR]

Non-invasive glucose monitoring sensors are promising techniques in diabetes management. In particular, optical-based near-infrared glucose sensors are label-free, compact, user-friendly, and inexpensive. They require no daily calibration and can provide continuous glucose level monitoring. However, these sensors are still in the development stage since their accuracy is still not widely accepted by medical professionals. Here, we introduce an optimized dual-channel approach for this kind of sensor where four optodes for short and long channels are employed. The long channel signal that contains useful information about the glucose level can be utilized to calculate the glucose contents in the dermis layer of the skin while the short channel is utilized to measure the interference “noise” signal originating from the epidermis layer. So, the latter can then be removed from the long channel signal. This work investigates the optimal source-detector separation (SDS) of both short and long channels for a wide range of wavelengths from 1200 nm to 1900 nm. Based on the sensitivity distributions of both dermis and epidermis layers and the signal-to-noise ratio, it is suggested that a 2 mm SDS distance with a wavelength of 1450 nm is a potential choice for the short channel. Moreover, 6 mm SDS at the wavelength of 1750 nm is the optimal choice for the long channel. This work may pave the way for further optimization of non-invasive near-infrared glucose sensors that will be widely adopted in the healthcare sector. [ABSTRACT FROM AUTHOR]

Time-of-flight (ToF) sensors using light pulses or continuous waves allow accurate distance measurements. Three-dimensional imagers can be based on an array of timing or time-gated integration pixels. Single-photon avalanche diodes (SPADs) have been increasingly chosen as the pixel’s photodetector device to develop fast, long-range ToF sensors. Solid-state ToF cameras are replacing other alternatives, showing attractive characteristics and bringing up new potential applications. This paper presents the technical evolution of SPAD ToF 3D imaging sensors, and provides insight into their development over the last few decades. Starting with the first SPAD imagers reported in the early 2000’s, various direct and indirect arrays up to present day state-of-the-art prototypes are referenced. The existing methods, options and possible implementations are described, addressing their advantages and drawbacks, and showing the progress yet to be made. The performance of the different presented approaches are given and compared. [ABSTRACT FROM AUTHOR]

Neurovascular coupling represents the relationship between changes in neuronal activity and cerebral hemodynamics. Concurrent Electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) recording and integration analysis has emerged as a promising multi-modal neuroimaging approach to study the neurovascular coupling as it provides complementary properties with regard to high temporal and moderate spatial resolution of brain activity. In this study we developed an EEG-informed-fNIRS analysis framework to investigate the neuro-correlate between neuronal activity and cerebral hemodynamics by identifying specific EEG rhythmic modulations which contribute to the improvement of the fNIRS-based general linear model (GLM) analysis. Specifically, frequency-specific regressors derived from EEG were used to construct design matrices to guide the GLM analysis of the fNIRS signals collected during a hand grasp task. Our results showed that the EEG-informed fNIRS GLM analysis, especially the alpha and beta band, revealed significantly higher sensitivity and specificity in localizing the task-evoked regions compared to the canonical boxcar model, demonstrating the strong correlations between hemodynamic response and EEG rhythmic modulations. Results also indicated that analysis based on the deoxygenated hemoglobin (HbR) signal slightly outperformed the oxygenated hemoglobin (HbO)-based analysis. The findings in our study not only validate the feasibility of enhancing fNIRS GLM analysis using simultaneously recorded EEG signals, but also provide a new perspective to study the neurovascular coupling of brain activity. [ABSTRACT FROM AUTHOR]

This review presents a practical primer for functional near-infrared spectroscopy (fNIRS) with respect to technology, experimentation, and analysis software. Its purpose is to jump-start interested practitioners considering utilizing a non-invasive, versatile, nevertheless challenging window into the brain using optical methods. We briefly recapitulate relevant anatomical and optical foundations and give a short historical overview. We describe competing types of illumination (trans-illumination, reflectance, and differential reflectance) and data collection methods (continuous wave, time domain and frequency domain). Basic components (light sources, detection, and recording components) of fNIRS systems are presented. Advantages and limitations of fNIRS techniques are offered, followed by a list of very practical recommendations for its use. A variety of experimental and clinical studies with fNIRS are sampled, shedding light on many brain-related ailments. Finally, we describe and discuss a number of freely available analysis and presentation packages suited for data analysis. In conclusion, we recommend fNIRS due to its ever-growing body of clinical applications, state-of-the-art neuroimaging technique and manageable hardware requirements. It can be safely concluded that fNIRS adds a new arrow to the quiver of neuro-medical examinations due to both its great versatility and limited costs. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study is to describe the noise reduction in the hemodynamic responses, obtained by functional near-infrared spectroscopy (fNIRS), using the proposed extended Kalman filter (EKF) with a non-linear state-space model, aided by the short separation (SS) measurement. Methods: The authors used the simulated data by adding the synthetic hemodynamic response function (HRF) to the multi-distance four-channel fNIRS signals obtained during the resting state. EKF was used to estimate the non-linear state-space model designed based on the Balloon model. The SS channel was used as a regressor that is sensitive only to superficial noises. The whole segments were grouped by the existence of motion artifacts (MAs) to investigate the improvement by EKF compared to the linear Kalman filter (LKF) and adaptive filter (AF) in extracting neural-evoked hemodynamic. Results: Kalman-based approaches were better than AF in reducing noises. Using EKF, the averages of the decreased errors and increased correlation between the recovered and true HRF were 34% in oxy-hemoglobin and 62% in deoxy-hemoglobin concentrations in segments having MAs, compared with LKF. In the MA-free condition, EKF is more robust to the poor quality of signals in noise reduction than LKF. Conclusion: The proposed non-linear Kalman approach is better in noise reduction than AF and LKF especially in noisy deoxy-hemoglobin concentrations, and less affected by the conditions of measurements and contaminations by MAs. Significance: The proposed method can be used for reducing superficial noises and MAs from fNIRS signals as an upgraded alternative to existing AFs. [ABSTRACT FROM AUTHOR]

In this paper, an in-pixel background light (BGL) subtraction architecture is presented for indoor/outdoor 2-D and 3-D imaging. The subtraction is performed using a pulsed modulation technique used in time-of-flight cameras. Mostly BGL subtraction is done using two capacitors. However, two capacitors cause mismatch effects; therefore, a single capacitor approach is proposed. Using a single capacitor, the BGL subtraction and distance estimation are performed in three operational phases. Hence, the proposed architecture can be used in applications where high-speed depth imaging is required. An image sensor with $24\times24$ pixel array is designed with 48- $\mu \text{m}$ pixel pitch and 17.36% fill factor. The measurement results of the chip fabricated in AMS 0.35- $\mu \text{m}$ CMOS OPTO process show up to 125-klx BGL subtraction without using an optical filter with a background-to-signal ratio of 40 dB. [ABSTRACT FROM AUTHOR]

This paper deals with the fault tolerance of a five-phase flux switching machine. Short-circuit currents calculation considering inductances variation is developed. Machine behavior (torque quality, copper losses, and homopolar current) under a single short-circuit phase fault, two consecutive and nonconsecutive phases short-circuited, is simulated with a two-dimensional finite elements (2-D FE) model and validated experimentally. Then, a new method is developed to improve its performances in faulty mode, by reconfiguring reference currents. In fact, an accurate torque model is established and then used in a genetic algorithm to optimize reference currents in faulty mode. In this approach of reference currents computation, the used algorithm has multiobjectives and multiconstraints, thereby allowing choosing the appropriate fault-tolerant current solution according to our application. The torque model is considered to be more accurate and closer to the 2-D FE results in both healthy and faulty modes. Then, a comparison of machine performances in healthy, degraded, and reconfigured modes is presented. Experimental results corroborate the analysis. [ABSTRACT FROM AUTHOR]

A compact circularly polarized antenna with a wide beamwidth and high return loss (RL) is presented. The antenna consists of four U-shaped metal strips sequentially rotated and fed with a 90^\circ phase difference feed network located beneath the ground plane. The antenna is designed to operate at around 915 MHz for UHF radio frequency identification applications, and the experimental results show that it has a wide beamwidth of over 114^\circ and high RL of over 34 dB in the 902–928 MHz range. [ABSTRACT FROM PUBLISHER]

Introducing Time-of-Flight 3-D image sensors to actual engineering applications, such as pattern recognition, is constrained not only by their limited depth and lateral resolution, but also by how similar the precision of depth measurement throughout the whole pixel-matrix is. In real operating environment, an observed 3-D-scene hardly exhibits a homogeneous reflectance factor. Moreover, the light-beam (laser source) presents a nonuniform optical power distribution in space. Thus, the amount of the incident light on the sensor surface varies drastically from one pixel to another, and so does the signal-to-noise ratio. To address this problem, this paper investigates the impact of both scene and light-source non-ideal characteristics on the sensor performance. An adaptive on-pixel analog signal processing technique is also presented and applied to the design of a 32 × 32 complementary metal oxide semiconductor (CMOS) range camera, featuring an interesting cost-efficient solution. [ABSTRACT FROM PUBLISHER]

A fully planar ultrawideband phased array with wide scan and low cross-polarization performance is introduced. The array is based on Munk's implementation of the current sheet concept, but it employs a novel feeding scheme for the tightly coupled horizontal dipoles that enables simple PCB fabrication. This feeding eliminates the need for “cable organizers” and external baluns, and when combined with dual-offset dual-polarized lattice arrangements the array can be implemented in a modular, tile-based fashion. Simple physical explanations and circuit models are derived to explain the array's operation and guide the design process. The theory and insights are subsequently used to design an exemplary dual-polarized infinite array with 5:1 bandwidth and VSWR<2.1 at broadside, and cross-polarization \approx-15~dB out to \theta=45^\circ in the D- plane. [ABSTRACT FROM PUBLISHER]

This paper presents a small wideband circularly polarized patch antenna printed on the low-cost FR-4 material for radio-frequency-identification smart bookshelves in libraries. The antenna is composed of four top-loaded patches sequentially rotated with a phase difference of 90? and double shorted to the ground. It operates at a center frequency of 0.915 GHz. The impedance bandwidth (SWR < 2) is 26.8%, the axial-ratio (AR) bandwidth (measured AR < 3 dB) is 11.6%, and the 3-dB beamwidth is 115°. The antenna gain is about 4 dBi, and the overall dimension is reduced by ~60% in length, in comparison with that of the conventional sequential patch antenna. [ABSTRACT FROM AUTHOR]

In this paper we present an analytical analysis of the fault masking capabilities of triple modular redundancy (TMR) hardening techniques in the presence of multiple cell upsets (MCUs) in the configuration memory of SRAM-based field-programmable gate arrays (FPGAs). The analytical method we developed allows an accurate study of the MCUs provoking domain crossing errors that defeat TMR. From our analysis we have found that most of the failures affect configurable logic block's routing resources. The experimental analysis has been performed on two realistic case study circuits. Experimental results are presented and discussed showing in particular that 2-bits MCUs may corrupt TMR 2.6 orders of magnitude more than single cell upsets (SCUs). [ABSTRACT FROM AUTHOR]