A low‐profile multi‐frequency leaky wave button antenna for body‐centric communications is presented. A leaky wave antenna loaded with U‐slots (a combination of U‐slots and slits) and tapered slot structures to improve the radiation efficiency, broadside radiation pattern, and widen the steering range is designed. Furthermore, it comprises a whole ground to meet the Specific Absorption Rate standard requirements based on the known standards. The antenna's performances are examined for on and off‐body conditions. For demonstration, a prototype is implemented, and the measurement is performed on the chest. The antenna operates at multi bands of 1.7–3.3 GHz (Industrial, Scientific, and Medical and 5G communication) and 4.15–10 GHz (sub‐6 GHz and X‐band communications). The peak gains of 6.9 and 8.2 dBi were obtained for on and off‐ body conditions, respectively. Furthermore, the antenna offers maximum radiation efficiencies of 89.3% and 99.3% for on‐body and free‐space conditions. The specific absorption rate (SAR) values obtained for body‐centric communications meet the regulation requirements (e.g., on body tissue at 3.2 GHz, it is 0.78 (1 g) and 0.44 (10 g) W/kg). With an overall miniaturized size, the proposed button antenna could be integrated with clothes. In addition, a multi‐wide bandwidth, circularly polarized radiation, a small size, high efficiency and gain, and low SAR values prove that the proposed antenna can be a potential candidate for wireless body area network and simultaneous wireless information and power transfer applications.
In this letter, we address blockage detection and precoder design for multiple-input multiple-output (MIMO) links, without communication overhead required. Blockage detection is achieved by classifying light detection and ranging (LIDAR) data through a physics-based graph neural network (GNN). For precoder design, a preliminary channel estimate is obtained by running ray tracing on a 3D surface obtained from LIDAR data. This estimate is successively refined and the precoder is designed accordingly. Numerical simulations show that blockage detection is successful with 95% accuracy. Our digital precoding achieves 90% of the capacity and analog precoding outperforms previous works exploiting LIDAR for precoder design.
This work presents the results of the study of plasma-chemical etching of molybdenum in SF6 inductively coupled plasma using a photoresist mask. The dependences of etching rate and selectivity on high-frequency (HF) power, pressure and temperature of the substrate holder are determined. It is shown that increasing the pressure from 1.5 to 3.5 Pa insignificantly decreases the etching rate of molybdenum and does not change the etching rate of photoresist. Changing the HF power from 500 to 1500 W leads to a significant increasing not only the molybdenum etching rate, but also the photoresist etching rate and, consequently, to decreasing the etching selectivity of molybdenum in relation to photoresist mask. It is determined that changing the temperature of the substrate holder in the range from − 28 to 40 °C leads to gradual increasing the etching rate of molybdenum and does not affect the etching of photoresist. Thus, the optimal ratio of technological parameters was selected in terms of achieving the highest molybdenum etching rate with maximum etching selectivity. Using the developed technology of ultra-selective etching, the removal of molybdenum film with a thickness of 200 nm was performed without reducing the thickness of the photoresist.
Although the technical and economic properties of the standard polymer photovol-taic (PV) materials (ethylene-vinyl acetate (EVA) encapsulant and fluorine-containing polyethylene terephthalate (PET) backsheet) meet the basic technical requirements, more sustainable polyolefin-based encapsulants and backsheets have been developed. These new polyolefin materials have to prove their performance compared to the established standard materials in terms of the electrical performance of the modules and in terms of reliability. The long-term stability of the new materials is tested and evaluated using accelerated aging tests and degradation modelling. Based on experimental results, the influence of the type of encapsulant and backsheet (i) on the electrical output power of PV test modules and (ii) on the aging-related electrical and material degradation under accelerated stress tests was estimated using statistical modelling approaches. First results showing significant effects for encapsulant, backsheet and the combination of both on the initial power output are presented. In general, modules with polypropylene-based backsheets have a higher initial power (P MPP) than those with PET-based backsheets, with the combination of thermoplastic polyolefin (TPO) encapsulation material and polyolefin backsheet being superior to the other material combinations. A comparison of the material-dependent degradation rates obtained from the mixed-effects models clearly shows that the degradation rate upon damp heat exposure for modules with EVA is significantly larger than that using polyolefin encapsulants. The derived relations aim to provide valuable input for innovative material developments as well as predictive maintenance specifications. K E Y W O R D S degradation, polyolefin backsheets, polyolefin encapsulants, statistical models
This work reports a resonant piezoelectric mirror driven by rotated directional interdigitated electrodes exploiting the d33 mode. This work expands the prior work on directional IDEs where only small angle, quasistatic devices were reported. We, for the first time combine this actuation principle with mechanical amplification and demonstrate that it can be used to excite high-speed and high amplitude scanning mirrors. A torsional twist of 0.66°, measured at the end of the actuators was mechanically amplified by over 30X to achieve an optical scan angle (OSA) of 20° at 29.7 kHz, with a Q-factor of 2481. This work marks the highest OSA achieved with directional interdigitated electrodes so far.
A detachable miniaturized three-element spirals radiator button antenna integrated with a compact leaky-wave wearable antenna forming a dual-band three-port antenna is proposed. The leaky-wave antenna is fabricated on a denim (ε r = 1.6, tan δ = 0.006) textile substrate with dimensions of 0.37 λ 0 × 0.25 λ 0 × 0.01 λ 0 mm 3 and a detachable rigid button of 20 mm diameter (on a PTFE substrate ε r = 2.01, tan δ = 0.001). It augments users' comfort, making it one of the smallest to date in the literature. The designed antenna, with 3.25 to 3.65 GHz and 5.4 to 5.85 GHz operational bands, covers the wireless local area network (WLAN) frequency (5.1-5.5 GHz), the fifth-generation (5G) communication band. Low mutual coupling between the ports and the button antenna elements ensures high diversity performance. The performance of the specific absorption rate (SAR) and the envelope correlation coefficient (ECC) are also examined. The simulation and measurement findings agree well. Low SAR, <−0.05 of LCC, more than 9.5 dBi diversity gain, dual polarization, and strong isolation between every two ports all point to the proposed antenna being an ideal option for use as a MIMO antenna for communications.
Reliability and durability of photovoltaic modules are a key factor for the development of emerging PV markets worldwide. Reliability is directly dependent on the chemical and physical stability of the polymeric encapsulation materials. One method capable of detecting ageing effects of the polymeric encapsulant directly on-site is UltraViolet Fluorescence (UVF) imaging. This work deals with advanced imaging analysis of UVF images and the subsequent correlation to electrical parameters of PV modules, which were exposed to climate-specific, long-term, accelerated aging procedures. For establishing a correlation, a so called UVF area ratio was established, resulting from the typical fluorescence patterns of the encapsulant material, which arise due to stress impact (e.g., water vapor ingress, elevated temperature, irradiation) and aging/degradation processes. Results of the data analysis show a clear correlation of the UVF area ratios and the electrical parameters with increasing aging time. In particular, the relationship between power and series resistance could be confirmed by extensive long-term test series with different climate-specific aging processes. Assuming the same type of polymeric encapsulation and backsheet and a comparable climate, determining the UVF area ratio can be used to estimate the service life and electrical power dissipation of each module installed in a PV array.
We report the design, fabrication, and characterization of a resonant varifocal micromirror excited with thin-film piezoelectric actuators. The mirror features a spiral suspension allowing both in-plane and out-of-plane motion which reduces the stress build up upon the membrane deformation and hence high shape fidelity. Driven at resonance, the mirror reaches an optical power of more than 27.5 diopters at 197 kHz and 7 VP-P excitation. The unique feature of the mirror is a combination of large optical power with the integration of a binary Fresnel zone plate (BFZP) onto the flexible membrane. The BFZP provides a virtual and real focusing point, which, when combined with the main mechanical mode provides four focusing points per harmonic cycle, effectively doubling the resonant frequency to 394 kHz. Compared to state-of-the-art devices, this device features the highest figure of merit ever reported.
Improving the explainability of Computer Vision models based on Deep Learning has recently become a compelling problem, ensuring reliable predictions to the end-user and enabling more fine-grained classifications. Recently, Concept Bottleneck models have been proposed for images classification, partitioning the problem in two stages and thereby defining a hierarchy of concepts. So far, however, little work has been done to investigate the applicability of this approach to other datasets with higher intra-class variability and ambiguity, and to discuss its flexibility to tasks different from whole-images classification. In this work we develop and discuss a Concept Bottleneck model for images segmentation, objects fine classification and tracking, and compare it to more classical methods based on Mask R-CNN and images similarity algorithms. All our models are trained and tested on a dataset comprised of pictures of fridges filled with various objects, however the method can be applied to any fine classification task. The proposed model makes full use of the hierarchy in concepts, exploiting the relationships between different categories at the same hierarchical level and relying on a novel method for handling multi-labels classifications. We show that the performance on fine classification is on par with a regular Mask R-CNN, but with a significant increase in explainability and in handling classes confusion. New explainable metrics are proposed to quantitatively evaluate the increase in explainability. We also demonstrate the effectiveness of the derived Concept Bottleneck features on related tasks, i.e., the tracking of objects between consecutive pictures in a sequence. The code is released as open source and available at https://opensource.silicon-austria.com/pittinof/hierarchical-concept-bottleneck.
In the above article  , the plot in Fig. 4(i) is accidentally inserted in Fig. 4(h), too. The correct plot for Fig. 4 is as shown below.
A soft piezoceramic multilayer (ML) bending thin and thick dual-actuators side-by-side device, for use in bone-conduction hearing aids (BCHA), was characterized experimentally. For this purpose, first, quasi-static (0.1 Hz square wave) transverse displacements (deflections) of each ML bender were measured using a laser vibrometer (LV) under unimorph and bimorph drivings at various non-amplified peak (p) voltages (1Vp–13Vp). The resulting peak displacement–voltage curves were found clearly nonlinear, indicating a pronounced piezoelectric (PE) field-dependent nonlinearity (FDNL). Then, experimental electric impedance analyses were conducted for each ML bender, using an impedance analyzer, under 1Vp unimorph driving for the whole audio frequency range (20 Hz–20 kHz). The identified three modes’ superposed impedance magnitudes and phases showed their increasing deviation to the frequency scale left with increasing the modes’ order, indicating a possible softening elastic FDNL, as confirmed later by harmonic frequency response LV measurements at 1Vp. Finally, the harmonic frequency responses, for the above audio frequency range, were measured for each ML bender using the LV under unimorph and bimorph drivings at various non-amplified voltages (1Vp–10Vp). Here, beside the PE FDNL, the frequency response functions showed clearly a pronounced softening elastic FDNL. Consequently, with increasing input voltages, the identified two modes’ displacement amplitudes were nonlinearly increasing, while resonant frequencies and corresponding quality factors were nonlinearly decreasing. The three parameters-voltage curves were found to fit well (R² ≈ 1) with high-order polynomials. These experimental results contradict the widely assumed displacement–potential linearity of middle ear or BCHA implantable PE vibrators of open literature available types (with or without shim bimorphs, unimorphs or diaphragms, and stacks) under similar targeted driving voltage and frequency ranges. The ML benders type quasi-static, frequency response and electric impedance characterizations, as well as the dual actuators side-by-side device, are proposed here for the first time for hearing aid applications.
Requirements for the miniaturization of electronics are constantly increasing as more and more functions are aimed to be integrated into a single device. At the same time, there are strong demands for low‐cost manufacturing, environmental compatibility, rapid prototyping, and small‐scale productions due to fierce competition, policies, rapid technical progress, and short innovation times. Altogether, those challenges cannot be sufficiently addressed by simply using either printed or silicon electronics. Instead, the synergies from combining those two technologies into so‐called hybrid electronics create novel opportunities for advanced capabilities and new areas of applications. In the first part of this review, printing and patterning technologies are presented with potential compatibility with conventional electronics manufacturing techniques. They can be utilized for the fabrication of highly complex structures. Nonetheless, up‐scalability, integration, and adaptation for industrial fabrication remain challenging due to technically limiting factors. Consequently, a special focus is placed on the up‐scalability, availability of commercial printing, and manufacturing machines, as well as processing challenges for high‐volume industrial applications. The second part of this review further provides an overview of exciting and innovative application possibilities of printed electronics, emphasizing sensor applications, as well as additively manufactured integrated circuits. The synergies from combining printed and silicon electronics create novel opportunities to realize highly complex structures. This review presents additive technologies with potential compatibility with conventional electronics manufacturing focusing on the up‐scalability and processing challenges for high‐volume industrial applications. Furthermore, exciting and innovative application possibilities of printed sensors as well as additively manufactured integrated circuits, are highlighted.
Modular Multilevel Converters (MMCs) are becoming more and more popular in medium-voltage applications thanks to several interesting features. The major limitation for applications with variable speed drives (VSDs) is the submodule capacitors’ voltage ripple, which depends directly on the output current/torque and inversely on the output frequency/speed. Among all the hybrid MMC topologies addressed in recent literature, the Flying-Capacitor Passive Cross-Connected arms (FC-PCC) MMC seems one of the most promising to cope with this issue. This article provides a comprehensive overview of its features and capabilities. The main open issues limiting safe and reliable converter operation in VSD applications are addressed, and novel solutions are presented, such as the optimization of the converter digital control strategy, the distributed implementation of the architecture, the L‑C oscillations damping during the pre-charge/start-up of the converter, and the optimized arm inductor design based on magnetic coupling concepts. The effectiveness of all the proposals is demonstrated through an accurate simulation of a 22 kW Permanent Magnet Synchronous Machine (PMSM) drive, including a complete model of the effects of the real-time communication and the processing latency. A prototype of the system has been developed employing some known and novel architectural solutions, as discussed in the last section of the paper.
This paper investigates the use of simulations of the electromagnetic emission (EMI) caused by the switching activity of a gallium nitride half bridge used in a power electronics application to predict the maximum generated conducted emission at the power supply lines. By using a simulation model of the voltage method defined in the CISPR25 standard, the important parasitic elements of the electronic components and the measurement setup are taken into account, but complicated modeling and simulation techniques are avoided. It shows that a simple circuit simulation is an effective alternative to predict emissions at an early design stage. Examples of simulation models and simulation setups as well as the measurement of the emissions are presented. The simulation data match the measurements well and provide a good estimate of electromagnetic interference already in the initial phase of new developments.
The design of a compact and wideband circularly polarized (CP) Monopulse antenna is presented. Firstly, the small-sized antenna element (13mm × 13mm), with the impedance bandwidth (BW) of 80.5% (4.3-10.1 GHz) and axial ratio (AR) bandwidth of 48.1% (6-9.8 GHz), and the gain of 7.2 dBic is designed. The array structure consists of two rat-race couplers; two metalized via holes that generate sum and difference patterns, and four branch-line couplers for CP characteristic improvement. The proposed antenna is capable of controlling CP diversity in both sum and difference beams. Additionally, with 50% BW and 25% 3-dB AR results and also with null-depth of less than -48 dB, it is a convenient design for tracking purposes.
Advanced packaging solutions require insulation and passivation materials with exceptional properties which can also fulfill the reliability needs of electronics devices such as MEMS, sensors or power modules. Since bonding (cohesive/adhesive) properties of packaging coatings are very important for reliable functioning of electronics devices, the bonding of aliphatic fluorinate-4 (AF4) parylene coatings was assessed in this work. As there is a lack of data regarding its bonding towards different substrates, pull-off tests of 1.6 and 2.5 µm thick AF4 coatings on silicon (Si) and glass (SiO2) substrates were performed. These showed a clear difference in the pull-off F/s curves between the AF4 coatings on Si and SiO2 substrates. This difference is parameterized by the pull-off energy, which will be presented in this work. To further understand the origin of the distinction in the pull-off energies between the AF4-Si and AF4-SiO2 samples and subsequently the cohesive/adhesive properties, mechanical and structural characterization was conducted on the AF4 coatings, where a clear difference in the E-modulus and crystallinity was observed. The Si and SiO2 wafers were shown to facilitate the CVD growth of the AF4 film distinctively, which likely relates to the divergent thermal properties of the substrates. Understanding of the cohesive/adhesive properties of AF4 coatings on different substrate materials advances the usage of the AF4 in electronics packaging technologies.
In this work, we consider a hybrid aerial full-duplex (FD) relaying consists of a reconfigurable intelligent surface (RIS) mounted over an FD unmanned aerial vehicle (UAV) relay operating in decode and forward mode to assist the information transfer between the base station and multiple users. For better spectral efficiency, we investigate the use of rate splitting multiple access (RSMA) in such networks and focus on joint optimization of RSMA parameters, 3D-coordinates of the UAV/RIS, and phase shift matrix at the RIS along with analyzing the outage probability, block error rate (BLER) and achievable weighted sum rate for finite blocklength (FBL) and infinite blocklength (IBL) codes under imperfect successive interference cancellation (SIC) at each user and residual-self interference (RSI) at UAV. We first formulate the weighted sum rate maximization problem and adopt the block coordinate descent (BCD) method to deal with non-convex nature of the problem. Thereafter, we propose the BCD-based algorithm that jointly optimizes these parameters using a heuristic approach for optimum power allocation, a Riemannian conjugate gradient-based algorithm to get the optimal phase shift at the RIS, and an iterative algorithm to obtain the optimal UAV/RIS position. It also distributes the common rate among the users optimally. Next, with obtained optimal parameters, we further analyze the performance of the network and derive the closed-form expressions of BLER, outage probability, and average weighted sum rate. We present Monte Carlo simulation-based results to validate the accuracy of the proposed algorithms and derived expressions, and demonstrate the superiority of RSMA over non-orthogonal multiple access (NOMA) and conventional orthogonal multiple access (OMA) schemes. Index Terms-Unmanned aerial vehicle (UAV), reconfigurable intelligent surfaces (RIS), rate splitting multiple access (RSMA), finite blocklength.
Nowadays Internet-of-Things and Industry 4.0 devices are often connected wirelessly. Current wireless sensor network (WSN) deployments are relying in most cases on the industrial, scientific and medical (ISM) bands without centralized resource scheduling. Thus, each device is a potential source of interference to other devices, both within its own WSN but also to devices in other collocated WSNs. If the transmission behaviour of devices from other WSNs is not random, we are able to find patterns in the time domain in their channel access. This is for example possible for periodic channel access, which is quite common for WSNs with demanding low-power and reliability requirements. The main goal of this work is to detect multiple sources of periodic interference in time slotted signal level measurements and estimate the time windows of future transmissions. This gives a WSN a certain understanding of the radio surrounding and can be used to adapt the transmission behaviour to thus avoid collisions. For this, the Multi Hypothesis Tracking algorithm is adapted and used together with timeslot-based interference measurements on low-cost sensor nodes. The applicability of the algorithm is shown with extensive simulations and the performance is demonstrated with measurements on a time division multiple access based WSN built upon the Bluetooth Low Energy physical layer.
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