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Electronics, Volume 8, Issue 12 (December 2019)

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Cover Story (view full-size image) WiFi-based sensing systems exploit the ambient 5G spectrum for detection and classification of [...] Read more.
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Open AccessArticle
Optimum Receiver-Side Tuning Capacitance for Capacitive Wireless Power Transfer
Electronics 2019, 8(12), 1543; https://doi.org/10.3390/electronics8121543 (registering DOI) - 13 Dec 2019
Abstract
This paper reveals the optimum capacitance value of a receiver-side inductor-capacitor (LC) network to achieve the highest efficiency in a capacitive power-transfer system. These findings break the usual convention of a capacitance value having to be chosen such that complete LC resonance happens [...] Read more.
This paper reveals the optimum capacitance value of a receiver-side inductor-capacitor (LC) network to achieve the highest efficiency in a capacitive power-transfer system. These findings break the usual convention of a capacitance value having to be chosen such that complete LC resonance happens at the operating frequency. Rather, our findings in this paper indicate that the capacitance value should be smaller than the value that forms the exact LC resonance. These analytical derivations showed that as the ratio of inductor impedance divided by plate impedance increased, the optimum Rx capacitance decreased. This optimum capacitance maximized the TX-to-RX transfer efficiency of a given set of system conditions, such as matching inductors and coupling plates. Full article
(This article belongs to the Special Issue Wireless Power/Data Transfer, Energy Harvesting System Design)
Open AccessArticle
Unified Power Flow Controller Based on Autotransformer Structure
Electronics 2019, 8(12), 1542; https://doi.org/10.3390/electronics8121542 (registering DOI) - 13 Dec 2019
Abstract
This paper proposes a new unified power flow controller (UPFC) topology. A single phase of them system with the proposed topology consists of an N:2 transformer with a center tap at the low-voltage side and a power converter module comprising full- and half-bridge [...] Read more.
This paper proposes a new unified power flow controller (UPFC) topology. A single phase of them system with the proposed topology consists of an N:2 transformer with a center tap at the low-voltage side and a power converter module comprising full- and half-bridge converters. A three-phase system can be implemented with three devices. While the conventional UPFC topology uses two three-phase transformers, which are called series and parallel transformers, the proposed topology utilizes three single-phase transformers to implement a three-phase UPFC system. By using an autotransformer structure, the power rating of the transformers and the voltage rating of switches in the power converter module can be significantly decreased. As a result, it is possible to reduce the installation spaces and costs compared with the conventional UPFC topology. In addition, by adopting a full- and half-bridge converter structure, the proposed topology can be easily implemented with conventional power devices and control techniques. The techniques used to control the proposed topology are described in this paper. The results obtained from simulations and experiments verify the effectiveness of the proposed UPFC topology. Full article
(This article belongs to the Special Issue High Power Electric Traction Systems)
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Open AccessFeature PaperArticle
A Wireless Sensors Network for Monitoring the Carasau Bread Manufacturing Process
Electronics 2019, 8(12), 1541; https://doi.org/10.3390/electronics8121541 (registering DOI) - 13 Dec 2019
Abstract
This work copes with the design and implementation of a wireless sensors network architecture to automatically and continuously monitor, for the first time, the manufacturing process of Sardinian Carasau bread. The case of a traditional bakery company facing the challenge of the Food-Industry [...] Read more.
This work copes with the design and implementation of a wireless sensors network architecture to automatically and continuously monitor, for the first time, the manufacturing process of Sardinian Carasau bread. The case of a traditional bakery company facing the challenge of the Food-Industry 4.0 competitiveness is investigated. The process was analyzed to identify the most relevant variables to be monitored during the product manufacturing. Then, a heterogeneous, multi-tier wireless sensors network was designed and realized to allow the real-time control and the data collection during the critical steps of dough production, sheeting, cutting and leavening. Commercial on-the-shelf and cost-effective integrated electronics were employed, making the proposed approach of interest for many practical cases. Finally, a user-friendly interface was provided to enhance the understanding, control and to favor the process monitoring. With the wireless senors network (WSN) we designed, it is possible to monitor environmental parameters (temperature, relative humidity, gas concentrations); cinematic quantities of the belts; and, through a dedicated image processing system, the morphological characteristics of the bread before the baking. The functioning of the WSN was demonstrated and a statistical analysis was performed on the variables monitored during different seasons. Full article
(This article belongs to the Special Issue Application of Wireless Sensor Networks in Monitoring)
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Open AccessArticle
A Miniaturized Wideband Bandpass Filter Using Quarter-Wavelength Stepped-Impedance Resonators
Electronics 2019, 8(12), 1540; https://doi.org/10.3390/electronics8121540 (registering DOI) - 13 Dec 2019
Abstract
In this paper, we present a simple method to design a miniaturized wideband bandpass filter with suppression of the third harmonic, using only two quarter-wavelength stepped-impedance resonators (SIRs). The resonant modes of the quarter-wavelength SIR, depending on the impedance ratio (K) and electrical [...] Read more.
In this paper, we present a simple method to design a miniaturized wideband bandpass filter with suppression of the third harmonic, using only two quarter-wavelength stepped-impedance resonators (SIRs). The resonant modes of the quarter-wavelength SIR, depending on the impedance ratio (K) and electrical length ratio (α), are discussed first. As to setting the resonant frequency of the SIR for the lower band edge of the required band, the size parameters of two quarter-wavelength SIRs can be determined by selecting the desired impedance ratio (K) and length ratio (α). By using the opposite directional arrangement of two SIRs with direct taped input/output ports, the wideband response can be formed. A filter example is shown in this study to address this simple design procedure. The measured results of the fabricated filter have a wide passband response from 3.3 to 5.8 GHz, with an insertion loss of 1.5 dB, a return loss of 20 dB, an extended bandwidth ration of 55%, a low-average group delay of less than 0.75 ns, and a stopband from 6 to 12 GHz, with an attenuation level of 20 dB. Due to the similar 0° feeding, a transmission zero at 8.3 GHz appears near the band edge; thus, improving the band selectivity. The proposed filter can have a very simple structure and a miniature size. Simulated results and measured results are in good agreement. Full article
(This article belongs to the Special Issue Filter Design Solutions for RF systems)
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Open AccessArticle
Using Approximate Computing and Selective Hardening for the Reduction of Overheads in the Design of Radiation-Induced Fault-Tolerant Systems
Electronics 2019, 8(12), 1539; https://doi.org/10.3390/electronics8121539 (registering DOI) - 13 Dec 2019
Abstract
Fault mitigation techniques based on pure software, known as software-implemented hardware fault tolerance (SIHFT), are very attractive for use in COTS (commercial off-the-shelf) microprocessors because they do not require physical modification of the system. However, these techniques cause software overheads that may affect [...] Read more.
Fault mitigation techniques based on pure software, known as software-implemented hardware fault tolerance (SIHFT), are very attractive for use in COTS (commercial off-the-shelf) microprocessors because they do not require physical modification of the system. However, these techniques cause software overheads that may affect the efficiency and costs of the overall system. This paper presents a design method of radiation-induced fault-tolerant microprocessor-based systems with lower execution time overheads. For this purpose, approximate computing and selective fault mitigation software-based techniques are used; thus it can be used in COTS devices. The proposal is validated through a case study for the TI MSP430 microcontroller. Results show that the designer can choose among a wide spectrum of design configurations, exploring different trade-offs between reliability, performance, and accuracy of results. Full article
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Open AccessFeature PaperArticle
A Feature Integrated Saliency Estimation Model for Omnidirectional Immersive Images
Electronics 2019, 8(12), 1538; https://doi.org/10.3390/electronics8121538 (registering DOI) - 13 Dec 2019
Viewed by 52
Abstract
Omnidirectional, or 360°, cameras are able to capture the surrounding space, thus providing an immersive experience when the acquired data is viewed using head mounted displays. Such an immersive experience inherently generates an illusion of being in a virtual environment. The popularity of [...] Read more.
Omnidirectional, or 360°, cameras are able to capture the surrounding space, thus providing an immersive experience when the acquired data is viewed using head mounted displays. Such an immersive experience inherently generates an illusion of being in a virtual environment. The popularity of 360° media has been growing in recent years. However, due to the large amount of data, processing and transmission pose several challenges. To this aim, efforts are being devoted to the identification of regions that can be used for compressing 360° images while guaranteeing the immersive feeling. In this contribution, we present a saliency estimation model that considers the spherical properties of the images. The proposed approach first divides the 360° image into multiple patches that replicate the positions (viewports) looked at by a subject while viewing a 360° image using a head mounted display. Next, a set of low-level features able to depict various properties of an image scene is extracted from each patch. The extracted features are combined to estimate the 360° saliency map. Finally, bias induced during image exploration and illumination variation is fine-tuned for estimating the final saliency map. The proposed method is evaluated using a benchmark 360° image dataset and is compared with two baselines and eight state-of-the-art approaches for saliency estimation. The obtained results show that the proposed model outperforms existing saliency estimation models. Full article
(This article belongs to the Special Issue Digital Media Processing for Immersive Communications)
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Open AccessArticle
Performance of Dual-Band Short-Wave Infrared InGaAs Focal-Plane Arrays with Interference Narrow-Band Filter
Electronics 2019, 8(12), 1537; https://doi.org/10.3390/electronics8121537 (registering DOI) - 13 Dec 2019
Viewed by 60
Abstract
In this work, we fabricated dual-band 800 × 2 short-wave infrared (SWIR) indium gallium arsenide (InGaAs) focal-plane arrays (FPAs) using N-InP/i-In0.53Ga0.47As/N-InP double-heterostructure materials, which are often applied in ocean-color remote sensing. Using narrow-band interference-filter integration, our detector-adopted planner structure [...] Read more.
In this work, we fabricated dual-band 800 × 2 short-wave infrared (SWIR) indium gallium arsenide (InGaAs) focal-plane arrays (FPAs) using N-InP/i-In0.53Ga0.47As/N-InP double-heterostructure materials, which are often applied in ocean-color remote sensing. Using narrow-band interference-filter integration, our detector-adopted planner structure produced two detection channels with center wavelengths of 1.24 and 1.64 μm, and a full-width half-maximum (FWHM) of 0.02 μm for both channels. The photoelectric characteristics of the spectral response, modulation transfer function (MTF), and detectability of the detector were further analyzed. Our FPAs showed good MTF uniformity with pixel operability as high as 100% for each 800 × 1 linear array. Peak detectivity reached 4.39 × 1012 and 5.82 × 1012 cm·Hz1/2/W at 278 K, respectively, and response nonuniformity was ideal at 2.48% and 2.61%, respectively. As a final step, dual-band infrared detection imaging was successfully carried out in push-broom mode. Full article
(This article belongs to the Special Issue Optical Imaging Instrumentation)
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Open AccessArticle
Autonomous Driving in Roundabout Maneuvers Using Reinforcement Learning with Q-Learning
Electronics 2019, 8(12), 1536; https://doi.org/10.3390/electronics8121536 (registering DOI) - 13 Dec 2019
Viewed by 76
Abstract
Navigating roundabouts is a complex driving scenario for both manual and autonomous vehicles. This paper proposes an approach based on the use of the Q-learning algorithm to train an autonomous vehicle agent to learn how to appropriately navigate roundabouts. The proposed learning algorithm [...] Read more.
Navigating roundabouts is a complex driving scenario for both manual and autonomous vehicles. This paper proposes an approach based on the use of the Q-learning algorithm to train an autonomous vehicle agent to learn how to appropriately navigate roundabouts. The proposed learning algorithm is implemented using the CARLA simulation environment. Several simulations are performed to train the algorithm in two scenarios: navigating a roundabout with and without surrounding traffic. The results illustrate that the Q-learning-algorithm-based vehicle agent is able to learn smooth and efficient driving to perform maneuvers within roundabouts. Full article
(This article belongs to the Special Issue Autonomous Vehicles Technology)
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Open AccessArticle
Predictive Control Method Based on Adjacent Vector Confinement Technique for a Three-Phase AC-DC Matrix Converter with High Efficiency
Electronics 2019, 8(12), 1535; https://doi.org/10.3390/electronics8121535 - 12 Dec 2019
Viewed by 108
Abstract
A model predictive current control method is proposed to reduce switching losses in an AC-DC matrix converter. In the proposed control strategy, several vectors are selected from among all possible switching vectors for a given location of the input current reference. The switching [...] Read more.
A model predictive current control method is proposed to reduce switching losses in an AC-DC matrix converter. In the proposed control strategy, several vectors are selected from among all possible switching vectors for a given location of the input current reference. The switching vector that minimizes the cost function is applied to the converter in the next sampling period. The principle of the proposed method involves clamping the selected switches to stop performing the switching operation to minimize the number of switchings in every sampling cycle. The total efficiency of the AC-DC matrix converter under the proposed strategy is 91.2% whereas that of the conventional strategy is 89.7%. In addition, unity-power-factor operation is guaranteed and smooth and sinusoidal waveforms are achieved. Finally, simulation and experimental results are demonstrated to confirm the validity of the proposed control strategy. Full article
(This article belongs to the Special Issue High Power Electric Traction Systems)
Open AccessArticle
Unified Predictive Current Control of PMSMs with Parameter Uncertainty
Electronics 2019, 8(12), 1534; https://doi.org/10.3390/electronics8121534 - 12 Dec 2019
Viewed by 95
Abstract
Predictive current control (PCC) applied on permanent magnet synchronous motors (PMSMs) has been developed into mainly three methods: the conventional finite-control-set PCC, the double voltage vectors PCC, and deadbeat PCC. However, each approach has its particular calculation way for voltage vectors selection and [...] Read more.
Predictive current control (PCC) applied on permanent magnet synchronous motors (PMSMs) has been developed into mainly three methods: the conventional finite-control-set PCC, the double voltage vectors PCC, and deadbeat PCC. However, each approach has its particular calculation way for voltage vectors selection and respective execution duration. This paper, based on the deadbeat idea, presents a unified predictive current control scheme of PMSMs. Under this scheme, the prior three classes are able to be clearly unified into one frame with lower calculation effort. Furthermore, to cope with problem of parameter mismatch in dq-axis current predictive model, a integrated identification method is proposed. Firstly, data selectors are designed to reject abnormal data of sampling signals, and then the interval-varying multi-innovation least squares algorithm is combined with forgetting factor (V-FF-MILS) to approximate the error terms caused by electromagnetic parameters error. The estimated results are online fed to the model of PMSM to enhance its accuracy. Finally, the processor in loop (PIL) simulation results verify that the proposed integrated scheme has advantages in current control of PMSMs with large-scale parameter uncertainty. Full article
(This article belongs to the Special Issue Advanced Control Systems for Electric Drives)
Open AccessArticle
Efficient FPGA-Based Architecture of the Overlap-Add Method for Short-Time Fourier Analysis/Synthesis
Electronics 2019, 8(12), 1533; https://doi.org/10.3390/electronics8121533 - 12 Dec 2019
Viewed by 87
Abstract
This paper proposes a simple and efficient FPGA-based architecture of the overlapping/windowing and overlap-add methods for real-time FFT/IFFT-based signal processing algorithms. The analyzed signal is divided into short-time overlapping frames that are windowed before applying Fourier analysis/synthesis. Then, the original signal is reconstructed [...] Read more.
This paper proposes a simple and efficient FPGA-based architecture of the overlapping/windowing and overlap-add methods for real-time FFT/IFFT-based signal processing algorithms. The analyzed signal is divided into short-time overlapping frames that are windowed before applying Fourier analysis/synthesis. Then, the original signal is reconstructed from the windowed (modified) frames using the overlap-add (OLA) technique. The proposed architecture was implemented on Field Programmable Gate Array (FPGA) using a high-level programming tool in MATLAB/SIMULINK environment. Its performance was evaluated on artificial and actual signals using objective metrics. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Open AccessFeature PaperArticle
Accurate Landing of Unmanned Aerial Vehicles Using Ground Pattern Recognition
Electronics 2019, 8(12), 1532; https://doi.org/10.3390/electronics8121532 - 12 Dec 2019
Viewed by 95
Abstract
Over the last few years, several researchers have been developing protocols and applications in order to autonomously land unmanned aerial vehicles (UAVs). However, most of the proposed protocols rely on expensive equipment or do not satisfy the high precision needs of some UAV [...] Read more.
Over the last few years, several researchers have been developing protocols and applications in order to autonomously land unmanned aerial vehicles (UAVs). However, most of the proposed protocols rely on expensive equipment or do not satisfy the high precision needs of some UAV applications such as package retrieval and delivery or the compact landing of UAV swarms. Therefore, in this work, a solution for high precision landing based on the use of ArUco markers is presented. In the proposed solution, a UAV equipped with a low-cost camera is able to detect ArUco markers sized 56 × 56 cm from an altitude of up to 30 m. Once the marker is detected, the UAV changes its flight behavior in order to land on the exact position where the marker is located. The proposal was evaluated and validated using both the ArduSim simulation platform and real UAV flights. The results show an average offset of only 11 cm from the target position, which vastly improves the landing accuracy compared to the traditional GPS-based landing, which typically deviates from the intended target by 1 to 3 m. Full article
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Open AccessArticle
SEE Sensitivity Evaluation for Commercial 16 nm SRAM-FPGA
Electronics 2019, 8(12), 1531; https://doi.org/10.3390/electronics8121531 - 12 Dec 2019
Viewed by 92
Abstract
Radiation effects can induce severe and diverse soft errors in digital circuits and systems. A Xilinx commercial 16 nm FinFET static random-access memory (SRAM)-based field-programmable gate array (FPGA) was selected to evaluate the radiation sensitivity and promote the space application of FinFET ultra [...] Read more.
Radiation effects can induce severe and diverse soft errors in digital circuits and systems. A Xilinx commercial 16 nm FinFET static random-access memory (SRAM)-based field-programmable gate array (FPGA) was selected to evaluate the radiation sensitivity and promote the space application of FinFET ultra large-scale integrated circuits (ULSI). Picosecond pulsed laser and high energy heavy ions were employed for irradiation. Before the tests, SRAM-based configure RAMs (CRAMs) were initialized and configured. The 100% embedded block RAMs (BRAMs) were utilized based on the Vivado implementation of the compiled hardware description language. No hard error was observed in both the laser and heavy-ion test. The thresholds for laser-induced single event upset (SEU) were ~3.5 nJ, and the SEU cross-sections were correlated positively to the laser’s energy. Multi-bit upsets were measured in heavy-ion and high-energy laser irradiation. Moreover, latch-up and functional interrupt phenomena were common, especially in the heavy-ion tests. The single event effect results for the 16 nm FinFET process were significant, and some radiation tolerance strategies were required in a radiation environment. Full article
(This article belongs to the Special Issue Extreme-Environment Electronics: Challenges and Solutions)
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Open AccessArticle
Improved RMS Delay Spread Estimation for mmWave Channels Using Savitzky–Golay Filters
Electronics 2019, 8(12), 1530; https://doi.org/10.3390/electronics8121530 - 12 Dec 2019
Viewed by 91
Abstract
In this paper, a novel method for improving the estimation accuracy of the root mean square (RMS) delay spread from the magnitude of the Channel Transfer Function (CTF) is presented. We utilize the level crossing rate metric in the frequency domain, which is [...] Read more.
In this paper, a novel method for improving the estimation accuracy of the root mean square (RMS) delay spread from the magnitude of the Channel Transfer Function (CTF) is presented. We utilize the level crossing rate metric in the frequency domain, which is based on scalar power measurement. The Savitzky–Golay (S-G) filtering method is used to improve the fidelity of the channel delay spread estimator. The presented concept is simple to implement and inexpensive. The proposed method is tested on the CTF magnitude data measured in the mmWave frequency band at low Signal-to-Noise Ratio (SNR). Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessArticle
Hardware-Based Single-Clock-Cycle Edge Detector for a PLC Central Processing Unit
Electronics 2019, 8(12), 1529; https://doi.org/10.3390/electronics8121529 - 12 Dec 2019
Viewed by 110
Abstract
This article discusses edge detectors implemented in programmable logic controllers. The behaviors of different vendors’ solutions are presented with pros and cons. The trigger functions defined in the IEC 61131-3 standard were analyzed for implementations. The main contribution of this paper is an [...] Read more.
This article discusses edge detectors implemented in programmable logic controllers. The behaviors of different vendors’ solutions are presented with pros and cons. The trigger functions defined in the IEC 61131-3 standard were analyzed for implementations. The main contribution of this paper is an idea for hardware acceleration of standard trigger functions that enables us to build single-clock-cycle edge detectors. Additionally, the structure for automatic edge detection on every input is shown. The structure with a synthesizable Verilog HDL description is presented. The comparison of the solution with vendor programmable logic controllers (PLCs) proves the effectiveness of the designed hardware-aided unit. Full article
(This article belongs to the Section Systems & Control Engineering)
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Open AccessArticle
Two-Bit Terahertz Encoder Realized by Graphene-Based Metamaterials
Electronics 2019, 8(12), 1528; https://doi.org/10.3390/electronics8121528 - 12 Dec 2019
Viewed by 95
Abstract
Terahertz (THz) technologies have achieved great progress in the past few decades. Developing active devices to control the THz waves is the frontier of THz applications. In this paper, a new scheme of two-bit THz encoder is proposed. Different from the present THz [...] Read more.
Terahertz (THz) technologies have achieved great progress in the past few decades. Developing active devices to control the THz waves is the frontier of THz applications. In this paper, a new scheme of two-bit THz encoder is proposed. Different from the present THz modulators whose spectra at different bands are varied simultaneously, our encoder can realize the individually efficient modulation of every channel. The encoder comprises the double-sided graphene-based metamaterials, in which the graphene structures on each side are connected to the external electrodes individually. The well-designed metamaterials on the front and back sides determine the resonances at two different bands (0.20 THz and 0.33 THz) separately. Through simulating the performance of this device by changing the conductivities of the graphene on each side independently, we demonstrate two-bit encoding realized by the dual-band modulation of transmission amplitude with electronic control, and the modulation depth can reach as high as 79.6%. Our encoder can promote the development of multifunctional and integrated devices, such as frequency division multiplexers and logical circuitry, which will contribute to THz communications. Full article
(This article belongs to the Special Issue Engineering Metamaterials)
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Open AccessFeature PaperArticle
Analysis of Resolution in Feedback Signals for Hardware-in-the-Loop Models of Power Converters
Electronics 2019, 8(12), 1527; https://doi.org/10.3390/electronics8121527 - 12 Dec 2019
Viewed by 100
Abstract
One of the main techniques for debugging power converters is hardware-in-the-loop (HIL), which is used for real-time emulation. Field programmable gate arrays (FPGA) are the most common design platforms due to their acceleration capability. In this case, the widths of the signals have [...] Read more.
One of the main techniques for debugging power converters is hardware-in-the-loop (HIL), which is used for real-time emulation. Field programmable gate arrays (FPGA) are the most common design platforms due to their acceleration capability. In this case, the widths of the signals have to be carefully chosen to optimize the area and speed. For this purpose, fixed-point arithmetic is one of the best options because although the design time is high, it allows the personalization of the number of bits in every signal. The representation of state variables in power converters has been previously studied, however other signals, such as feedback signals, can also have a big influence because they transmit the value of one state variable to the rest, and vice versa. This paper presents an analysis of the number of bits in the feedback signals of a boost converter, but the conclusions can be extended to other power converters. The purpose of this work is to study how many bits are necessary in order to avoid the loss of information, but also without wasting bits. Errors of the state variables are obtained with different sizes of feedback signals. These show that the errors in each state variable have similar patterns. When the number of bits increases, the error decreases down to a certain number of bits, where an almost constant error appears. However, when the bits decrease, the error increases linearly. Furthermore, the results show that there is a direct relation between the number of bits in feedback signals and the inputs of the converter in the global error. Finally, a design criterion is given to choose the optimum width for each feedback signal, without wasting bits. Full article
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Open AccessArticle
A Two-Degree-of-Freedom Cantilever-Based Vibration Triboelectric Nanogenerator for Low-Frequency and Broadband Operation
Electronics 2019, 8(12), 1526; https://doi.org/10.3390/electronics8121526 - 11 Dec 2019
Viewed by 150
Abstract
With the continual increasing application requirements of broadband vibration energy harvesters (VEHs), many attempts have been made to broaden the bandwidth. As compared to adopted only a single approach, integration of multi-approaches can further widen the operating bandwidth. Here, a novel two-degree-of-freedom cantilever-based [...] Read more.
With the continual increasing application requirements of broadband vibration energy harvesters (VEHs), many attempts have been made to broaden the bandwidth. As compared to adopted only a single approach, integration of multi-approaches can further widen the operating bandwidth. Here, a novel two-degree-of-freedom cantilever-based vibration triboelectric nanogenerator is proposed to obtain high operating bandwidth by integrating multimodal harvesting technique and inherent nonlinearity broadening behavior due to vibration contact between triboelectric surfaces. A wide operating bandwidth of 32.9 Hz is observed even at a low acceleration of 0.6 g. Meanwhile, the peak output voltage is 18.8 V at the primary resonant frequency of 23 Hz and 1 g, while the output voltage is 14.9 V at the secondary frequency of 75 Hz and 2.5 g. Under the frequencies of these two modes at 1 g, maximum peak power of 43.08 μW and 12.5 μW are achieved, respectively. Additionally, the fabricated device shows good stability, reaching and maintaining its voltage at 8 V when tested on a vacuum compression pump. The experimental results demonstrate the device has the ability to harvest energy from a wide range of low-frequency (<100 Hz) vibrations and has broad application prospects in self-powered electronic devices and systems. Full article
(This article belongs to the Section Systems & Control Engineering)
Open AccessArticle
Energy Rate Maximization with Sum-Rate Constraint for SWIPT in Multiple-Access Channels
Electronics 2019, 8(12), 1525; https://doi.org/10.3390/electronics8121525 - 11 Dec 2019
Viewed by 143
Abstract
This paper considers simultaneous wireless information and power transfer (SWIPT) systems in the two-user Gaussian multiple access channel (G-MAC). In SWIPT systems, for a transmit signal each transmitter consists of an information-carrying signal and energy-carrying signal. By controlling a different set of the [...] Read more.
This paper considers simultaneous wireless information and power transfer (SWIPT) systems in the two-user Gaussian multiple access channel (G-MAC). In SWIPT systems, for a transmit signal each transmitter consists of an information-carrying signal and energy-carrying signal. By controlling a different set of the power for the information transmission and power for the energy transmission under a total power constraint, the information sum-rate and energy transmission rate can be achieved. As the information carrying-to-transmit power ratio at transmitters and the information sum-rate increases, however, the energy transmission rate decreases. In other words, there is a fundamental trade-off between the information sum-rate and the energy transmission rate according to the power-splitting ratio at each transmitter. Motivated by this, this paper proposes an optimal power-splitting scheme that maximizes the energy transmission rate subject to a minimum sum-rate constraint. In particular, a closed-form expression of the power-splitting coefficient is presented for the two-user G-MAC under a minimum sum-rate constraint. Numerical results show that the energy rate of the proposed optimal power-splitting scheme is greater than that of the fixed power-splitting scheme. Full article
Open AccessArticle
An Electromagnetic Lock Actuated by a Mobile Phone Equipped with a Self-Made Laser Pointer
Electronics 2019, 8(12), 1524; https://doi.org/10.3390/electronics8121524 - 11 Dec 2019
Viewed by 125
Abstract
The main purpose of this study was to create an acousto-optic control lock device to convert electrical signals with a specific sound command using an acousto-optic conversion module, thereby improving the reliability and safety of opening or closing remote controlled door locks, such [...] Read more.
The main purpose of this study was to create an acousto-optic control lock device to convert electrical signals with a specific sound command using an acousto-optic conversion module, thereby improving the reliability and safety of opening or closing remote controlled door locks, such as car central locks or rolling doors. We used music playing through a smart phone speaker to create a special laser pointer to connect with the smart phone‘s auxiliary input. The laser pointer (wavelength of 630–650 nm and maximum output of 5 mw) lights up when the smart phone’s music starts playing at a music frequency matching the light frequency. When the solar panel receives light, it converts the frequency of the light signal into an electrical frequency signal. The current is amplified using the power amplifier and then the amplified current flows to the sound recognition module. The sound recognition module performs audio comparison on the set sound signal, and once the comparison is correct, the output voltage activates the electromagnetic switch on the door to open or close it. Full article
(This article belongs to the Special Issue Intelligent Electronic Devices)
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Open AccessFeature PaperArticle
A Phasor Measurement Unit Algorithm Using IIR Filters for FPGA Implementation
Electronics 2019, 8(12), 1523; https://doi.org/10.3390/electronics8121523 - 11 Dec 2019
Viewed by 113
Abstract
Phasor measurement units (PMU) are increasingly used in electrical power transmission networks, to maintain stability and protect the network. PMUs accurately measure voltage, phase, frequency, and rate of change of frequency (ROCOF). For reliability, it is desirable to implement a PMU using an [...] Read more.
Phasor measurement units (PMU) are increasingly used in electrical power transmission networks, to maintain stability and protect the network. PMUs accurately measure voltage, phase, frequency, and rate of change of frequency (ROCOF). For reliability, it is desirable to implement a PMU using an FPGA. This paper describes a novel algorithm, suited to implementation in an FPGA and based on a simple PMU block diagram. A description of its realization using low hardware complexity infinite impulse response (IIR) filters is given. The IEC/IEEE standard 60255-118-1:2018 Part 118-1: Synchrophasor measurements for power systems, describes “reference” Finite Impulse Response (FIR) filters for implementing PMU hardware. At the 10 kHz sampling frequency used for our implementation, each “reference” FIR filter requires 100 multipliers, while an 8th order IIR filter only requires 12 multipliers. This paper compares the performance of different order IIR filter-based PMUs with the performance of the same PMU algorithm using the IEC/IEEE FIR reference filter. The IIR-based PMU easily satisfies all the requirements of IEC/IEEE standard and has a much better out of band signal rejection performance than a FIR-based PMU. Steady state errors for a rated voltage ± 10% and a rated frequency ± 5 Hz are < 0.000001% for total vector error (TVE) and < 1 µHz for frequency, with a latency of two mains cycles. Full article
(This article belongs to the Section Computer Science & Engineering)
Open AccessFeature PaperArticle
Accelerating Retinal Fundus Image Classification Using Artificial Neural Networks (ANNs) and Reconfigurable Hardware (FPGA)
Electronics 2019, 8(12), 1522; https://doi.org/10.3390/electronics8121522 (registering DOI) - 11 Dec 2019
Viewed by 240
Abstract
Diabetic retinopathy (DR) and glaucoma are common eye diseases that affect a blood vessel in the retina and are two of the leading causes of vision loss around the world. Glaucoma is a common eye condition where the optic nerve that connects the [...] Read more.
Diabetic retinopathy (DR) and glaucoma are common eye diseases that affect a blood vessel in the retina and are two of the leading causes of vision loss around the world. Glaucoma is a common eye condition where the optic nerve that connects the eye to the brain becomes damaged, whereas DR is a complication of diabetes caused by high blood sugar levels damaging the back of the eye. In order to produce an accurate and early diagnosis, an extremely high number of retinal images needs to be processed. Given the required computational complexity of image processing algorithms and the need for high-performance architectures, this paper proposes and demonstrates the use of fully parallel field programmable gate arrays (FPGAs) to overcome the burden of real-time computing in conventional software architectures. The experimental results achieved through software implementation were validated on an FPGA device. The results showed a remarkable improvement in terms of computational speed and power consumption. This paper presents various preprocessing methods to analyse fundus images, which can serve as a diagnostic tool for detection of glaucoma and diabetic retinopathy. In the proposed adaptive thresholding-based preprocessing method, features were selected by calculating the area of the segmented optic disk, which was further classified using a feedforward neural network (NN). The analysis was carried out using feature extraction through existing methodologies such as adaptive thresholding, histogram and wavelet transform. Results obtained through these methods were quantified to obtain optimum performance in terms of classification accuracy. The proposed hardware implementation outperforms existing methods and offers a significant improvement in terms of computational speed and power consumption. Full article
(This article belongs to the Section Computer Science & Engineering)
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Open AccessFeature PaperArticle
Constant Envelope Modulation Techniques for Limited Power Millimeter Wave Links
Electronics 2019, 8(12), 1521; https://doi.org/10.3390/electronics8121521 - 11 Dec 2019
Viewed by 120
Abstract
The demand for increased capacity and link availability for mobile communications requires the utilization of higher frequencies, such as millimeter waves at extremely high frequencies (EHFs) above 30 GHz. In this regime of frequencies, the waves are subjected to high atmospheric attenuation and [...] Read more.
The demand for increased capacity and link availability for mobile communications requires the utilization of higher frequencies, such as millimeter waves at extremely high frequencies (EHFs) above 30 GHz. In this regime of frequencies, the waves are subjected to high atmospheric attenuation and dispersion effects that lead to a degradation in communication reliability. The fact that solid-state millimeter and sub-millimeter wave sources are producing low power calls for effective signaling utilizing waveforms with a low peak to average power ratio (PAPR), such as constant envelope (CE) modulation. The CE techniques present a PAPR of 0 dB resulting in peak power transmission with high energy efficiency. The study of the performances of constant envelope orthogonal modulation techniques in the presence of co-channel interference is presented. The performance is evaluated in terms of the average symbol error rate (SER) using analytical results and simulations. The theory is carried out for the CE-M-ary time orthogonal (CE-MTO) and CE-orthogonal frequency division multiplexing (CE-OFDM), demonstrating comparable performances while leading to a simpler implementation than that of the CE-OFDM. Full article
(This article belongs to the Special Issue Millimeter and Terahertz Wireless Communications)
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Open AccessArticle
Realization of High-Performance Broadband Quadrature Directional Couplers in UMS PH25 Technology
Electronics 2019, 8(12), 1520; https://doi.org/10.3390/electronics8121520 - 11 Dec 2019
Viewed by 119
Abstract
The problem of the realization of broadband quadrature directional couplers in UMS (United Monolithic Semiconductors) PH25 is thoroughly investigated. The limitations of the selected technology are discussed with respect to directional couplers’ design. It is shown that, in such technologies, two major problems [...] Read more.
The problem of the realization of broadband quadrature directional couplers in UMS (United Monolithic Semiconductors) PH25 is thoroughly investigated. The limitations of the selected technology are discussed with respect to directional couplers’ design. It is shown that, in such technologies, two major problems have to be overcome to achieve the high-performance of the resulting integrated couplers, i.e., the realization of appropriate coupling together with appropriate characteristic impedances, and the equalization of inductive and capacitive coupling coefficients that are inherently different in inhomogeneous dielectric structures. Three different solutions that allow for achieving strong coupling in the selected UMS PH25 process were selected and experimentally investigated, showing the possibility of such circuits’ realization. In each of the presented integrated couplers, capacitive compensation techniques were applied for coupling coefficients’ equalization. Full article
(This article belongs to the Special Issue RF/Mm-Wave Circuits Design and Applications)
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Open AccessArticle
Tunnel-Free Distributed Mobility Management (DMM) Support Protocol for Future Mobile Networks
Electronics 2019, 8(12), 1519; https://doi.org/10.3390/electronics8121519 - 11 Dec 2019
Viewed by 115
Abstract
The number of wireless services and devices have remarkably increased, especially since the introduction of smart phones. The population of mobile nodes (MNs) is now exceeding the traditional non-mobile nodes. Mobility is a key factor in mobile core networks as it is responsible [...] Read more.
The number of wireless services and devices have remarkably increased, especially since the introduction of smart phones. The population of mobile nodes (MNs) is now exceeding the traditional non-mobile nodes. Mobility is a key factor in mobile core networks as it is responsible for providing continuous communication when a MN is on the move. Currently, a centralized mobile core network architecture is implemented, which has certain limitations. Distributed mobility management (DMM) is often seen as a solution to the problems associated with centralized mobility management (CMM). Address and tunneling management are big challenges for current DMM-based mobility protocols. Keeping in mind the current advancement of mobile network architecture, this paper proposes a novel tunnel-free distributed mobility management support protocol intended for such an evolution. In addition, the performance of the existing DMM IPv6 mobility management protocols in the context of handover latency, handover blocking probability, and data packet loss is analyzed and compared to the proposed framework. The performance analyses show that the proposed tunnel-free method can reduce about 12% of handover latency, 71% of handover blocking probability, and 82% of data packet loss. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessTechnical Note
Dynamic Performance Evaluation of Various GNSS Receivers and Positioning Modes with Only One Flight Test
Electronics 2019, 8(12), 1518; https://doi.org/10.3390/electronics8121518 - 11 Dec 2019
Viewed by 123
Abstract
The performance of global navigation satellite system (GNSS) receivers in dynamic modes is mostly assessed using results obtained from independent maneuvering of vehicles along similar trajectories at different times due to limitations of receivers, payload, space, and power of moving vehicles. However, such [...] Read more.
The performance of global navigation satellite system (GNSS) receivers in dynamic modes is mostly assessed using results obtained from independent maneuvering of vehicles along similar trajectories at different times due to limitations of receivers, payload, space, and power of moving vehicles. However, such assessments do not ensure valid evaluation because the same GNSS signal environment cannot be ensured in a different test session irrespective of how accurately it mimics the original session. In this study, we propose a valid methodology that can evaluate the dynamic performance of multiple GNSS receivers in various positioning modes with only one dynamic test. We used the record-and-replay function of RACELOGIC’s LabSat3 Wideband and developed a software that can log and re-broadcast Radio Technical Commission for Maritime Services (RTCM) messages for the augmented systems. A preliminary static test and a drone test were performed to verify proper operation of the system. The results show that the system could efficiently evaluate the performances of stand-alone, differential GNSS, and real time kinematics positioning for three GNSS receivers in two different positioning modes by repeatedly re-radiating the recorded signals acquired through only one flight. Our proposed system is expected to be useful in evaluating dynamic navigation performance accurately and conveniently in a valid manner. Full article
(This article belongs to the Special Issue Sensor-Based Navigation and Control with Applications)
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Open AccessFeature PaperArticle
An Energy Community Implementation: The Unical Energy Cloud
Electronics 2019, 8(12), 1517; https://doi.org/10.3390/electronics8121517 - 11 Dec 2019
Viewed by 170
Abstract
Reducing greenhouse gas emissions, limiting the effects of climate change and decreasing the environmental, social and economic costs of energy production are some of the main issues related to the sustainable development of modern society. Energy communities, envisioned to enable local energy exchange [...] Read more.
Reducing greenhouse gas emissions, limiting the effects of climate change and decreasing the environmental, social and economic costs of energy production are some of the main issues related to the sustainable development of modern society. Energy communities, envisioned to enable local energy exchange between consumers and producers of renewable energy, represent a possible scenario towards a cleaner and sustainable energy system. In this paper, an energy community management model called Power Cloud and presented in previous papers is proposed for a real-world practical application at the University of Calabria. In particular, the implementation of the information and communication technology (ICT) architecture and other enabling technologies, such as the nanogrid and the smart energy box, are discussed in detail. The experiment results show that by adopting the Power Cloud management model it is possible to obtain significant savings in terms of energy cost, which provide benefit for a community, such as a university campus. Full article
(This article belongs to the Special Issue Active Regional Energy Systems and Microgrids)
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Open AccessArticle
Energy Management Strategy Design and Simulation Validation of Hybrid Electric Vehicle Driving in an Intelligent Fleet
Electronics 2019, 8(12), 1516; https://doi.org/10.3390/electronics8121516 - 10 Dec 2019
Viewed by 149
Abstract
This paper proposes a combination method of longitudinal control and fuel management for an intelligent Hybrid Electric Vehicle (HEV) fleet. This method can reduce the fuel consumption while maintaining the distance and speed for each vehicle in the fleet. An HEV system efficiency [...] Read more.
This paper proposes a combination method of longitudinal control and fuel management for an intelligent Hybrid Electric Vehicle (HEV) fleet. This method can reduce the fuel consumption while maintaining the distance and speed for each vehicle in the fleet. An HEV system efficiency model was established to simulate the impact of different working modes. Based on the principle of optimal vehicle system efficiency, the energy management control strategy of HEV was designed. Then, the driver model of the piloting vehicle and the following vehicle was built by using an intelligent fuzzy control method. Finally, the intelligent fleet model and energy matching model of HEV were integrated with the simulation platform that was developed based on MATLAB/Simulink/Stateflow. The validity of the energy matching strategy of HEV under the principle of optimal system efficiency was verified by simulation results, and the purpose of improving the driving safety, traffic efficiency, and fuel economy of the fleet was achieved. Comparing with the conventional control strategy, the proposed method saved 7.79% of fuel for the HEV fleet. Meanwhile, the distance ranges between the vehicles were from 12 meters to 15 meters, which improved the driving safety, passing rate, and fuel economy. Full article
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Open AccessFeature PaperArticle
Role of the Product λ(0)ρ(1) in Determining LDPC Code Performance
Electronics 2019, 8(12), 1515; https://doi.org/10.3390/electronics8121515 - 10 Dec 2019
Viewed by 131
Abstract
The objective of this work is to analyze the importance of the product λ ( 0 ) ρ ( 1 ) in determining low density parity check (LDPC) code performance, as far as its influence on the weight distribution function and [...] Read more.
The objective of this work is to analyze the importance of the product λ ( 0 ) ρ ( 1 ) in determining low density parity check (LDPC) code performance, as far as its influence on the weight distribution function and on the decoding thresholds. This analysis is based on the 2006 paper by Di et al., as far as the weight distribution function is concerned, and on the 2018 paper by Vatta et al., regarding the LDPC decoding thresholds. In particular, the first paper Di et al. analyzed the relation between the above mentioned product and the minimum weight of an ensemble of random LDPC codewords, whereas in the second some analytical upper bounds to the LDPC decoding thresholds were determined. In the present work, besides analyzing the performance of an ensemble of LDPC codes through the outcomes of Di et al.’s 2006 paper, we give the relation between one of the upper bounds found in Vatta et al.’s 2018 paper and the above mentioned product λ ( 0 ) ρ ( 1 ) , thus showing its role in also determining an upper bound to LDPC decoding thresholds. Full article
(This article belongs to the Section Computer Science & Engineering)
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Open AccessArticle
Management of the Output Electrical Power in Thermoelectric Generators
Electronics 2019, 8(12), 1514; https://doi.org/10.3390/electronics8121514 - 10 Dec 2019
Viewed by 164
Abstract
Thermoelectric Generators (TEGs) are devices for direct conversion of heat into electrical power and bear a great potential for applications in energy scavenging and green energy harvesting. Given a heat source, the conversion efficiency depends on the available temperature difference, and must be [...] Read more.
Thermoelectric Generators (TEGs) are devices for direct conversion of heat into electrical power and bear a great potential for applications in energy scavenging and green energy harvesting. Given a heat source, the conversion efficiency depends on the available temperature difference, and must be maximized for optimal operation of the TEG. In this frame, the choice of materials with high thermoelectric properties should be accompanied by the identification of criteria for an optimal exploitation of the electrical power output. In this work, we briefly review the main properties of TEGs, focusing on the electrical power output and the thermal-to-electrical conversion efficiency. Besides, we discuss principles of operation of TEGs enabling the optimization of the electrical power output, based on the suitable choice of the electrical load. In particular, we comparatively present and discuss the conditions for matching the electrical load—yielding to maximum power transfer—and those for maximizing the conversion efficiency. We compare the two conditions applying them to the exploitation of a heat reservoir for energy storage and to the recovery of heat from a heat exchanger. We conclude that the difference between the two conditions is not significant enough to justify the complexity required by the implementation of the maximum efficiency. In addition, we consider the effect of the thermal contact resistance on the electrical power output. Using a simple thermal-electrical model, we demonstrate that the equivalent electrical resistance measured between the terminals of the TEG depends on the thermal exchange. Hence, for maximum power transfer, the electrical load of the TEG should not match its parasitic resistance, but the equivalent electrical resistance in each specific operating conditions, which determine the thermal fluxes. The model can be applied for the development of efficient alternative algorithms for maximum power point tracking. Full article
(This article belongs to the Section Power Electronics)
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