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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - All Dielectric Mode Order Transformation Photonic Structure Design by Evolutionary Optimization Approach
摘要： In this manuscript, an evolutionary algorithm is applied to design a mode order converter photonic crystal structure for achieving transformation of the propagating fundamental mode to the higher order mode. In order to transform incident light mode from an even mode to an odd mode, predefined mask object functions are employed. The cross-sectional field profiles at the output face of the optimized structure are utilized to evaluate the optimization cost function to achieve mode order transformation task. In the study, the optimized structure composed of dielectric alumina (Al2O3) rods and time domain analyses of the optimization process are done by using finite-difference time domain method. Furthermore, numerical results are confirmed by experiments for designed structure at the microwave frequencies. It is shown that the numerical calculations and experimental measurements agree well with each other.
关键词： mode order converter,differential evolution algorithm,phase shift,photonic crystals,integrated optics
更新于2025-09-23 15:19:57
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[IEEE 2018 New Generation of CAS (NGCAS) - Valletta, Malta (2018.11.20-2018.11.23)] 2018 New Generation of CAS (NGCAS) - High-Resolution ADCs for Biomedical Imaging Systems
摘要： With the rapid development of biomedical imaging systems, the requirement of the accuracy of an Analog-to-Digital Converter (ADC) becomes more and more critical. Traditional Nyquist-rate analog to digital data converters cannot meet the requirement any more. Sigma-Delta analog to digital data converter, which makes a trade-off between speed and accuracy, can achieve an ideal accuracy by employing the oversampling and noise-shaping technology. In this work, a Verilog-AMS model for sigma-delta modulator is built, including the topologic, the order of stage, oversampling rate, system parameters, etc. On the basic of theoretical analysis and scienti?c ?ow path, ?nally, a third-order 1-bit sigma-delta modulator is designed and optimized, whose performance agrees well with the theoretical module.
关键词： Analog-to-Digital Converter,Σ? ADC,Successive Approximation Register(SAR) ADC,Oversampling,Biomedical Imaging Systems
更新于2025-09-23 15:19:57
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Enhanced Power Output from the PV with Low Input Ripple DC-DC Converter
摘要： The primary objective of Maximum Power Point Tracking (MPPT) for PV systems connected to a low-voltage DC grid is to extract the maximum possible power output from the PV array. Normally high-frequency switched mode power converters are employed to track the maximum power. These converters, however, impose switching frequency voltage ripple on the PV output. This causes fluctuation around the Maximum Power Point (MPP) and results in power loss. These losses can be reduced using electrolytic capacitors, however, the electrolytic capacitors’ lifespan is relatively shorter than that of a PV panel. In this paper, an interleaved boost converter is used to reduce high-frequency voltage ripple introduced on panel. Hence, smaller values of longer lifespan capacitors such as film capacitors will be sufficient to curtail the smaller ripple. Moreover, film capacitors are selected based on voltage ripple. Analysis was carried out for calculating voltage ripple imposed on PV module to select input filter more precisely. In addition, reduction in the voltage ripple is calculated quantitatively and is compared with that of a conventional boost converter. Enhanced power output from the PV panel is mathematically proven and experimentally demonstrated.
关键词： photovoltaic panel,switching frequency voltage ripple,PV output power,electrolytic capacitors,film capacitor,maximum power point tracking (MPPT),interleaved boost converter (IBC),low-voltage dc grid,DC-DC converter,photovoltaic (PV) system
更新于2025-09-19 17:15:36
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - On-chip forward bandpass mode conversion based on two cascaded Bragg gratings
摘要： Forward conversion between two guided modes can be achieved with the aid of an additional mode based on two cascaded Bragg reflection processes. We have investigated and verified the mode conversion by simulation and experiment.
关键词： mode converter,Bragg grating,silicon photonics
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE XXVII International Scientific Conference Electronics (ET) - Sozopol (2018.9.13-2018.9.15)] 2018 IEEE XXVII International Scientific Conference Electronics - ET - Improving control of excitation sources in transient and lock-in thermography
摘要： The aim of the paper is to study the possibilities for using one excitation source for transient as well as lock-in infrared thermography modes. Problems in controlling the high-power optical excitation sources in active thermography are analysed. Special attention is paid to high power LEDs as sources for thermal stimulation in thermography. A method for improving control of high-power optical and electrical types of excitation sources is proposed with possibility of voltage or current stabilization.
关键词： active thermography,excitation source,current sensing,multiphase DC/DC converter,power LED
更新于2025-09-19 17:15:36
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[IEEE 2018 5th NAFOSTED Conference on Information and Computer Science (NICS) - Ho Chi Minh, Vietnam (2018.11.23-2018.11.24)] 2018 5th NAFOSTED Conference on Information and Computer Science (NICS) - Reconfigurable Mode Converter Using Two Silicon Y-Junction Couplers for Mode Division Multiplexing Network
摘要： Mode converters are one of the most fundamental and indispensable components in the mode division multiplexing system. We design a new mode converter that is capable of converting between mode TE0 to TE1/TE2 or TE1 to TE1/TE2 with the performance achieved in both cases over 99% at the wavelength 1550nm. Not only conversion efficiency is high but also the effect of the unwanted modes is very small, it is always below 0.03dB. In addition, with outstanding advantages of the proposed structure such as large manufacturing tolerances and compact size will be good candidate for applications in on-chip MDM network.
关键词： Y-junction,mode converter,WDM
更新于2025-09-19 17:15:36
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A CMOS SPAD Imager with Collision Detection and 128 Dynamically Reallocating TDCs for Single-Photon Counting and 3D Time-of-Flight Imaging
摘要： Per-pixel time-to-digital converter (TDC) architectures have been exploited by single-photon avalanche diode (SPAD) sensors to achieve high photon throughput, but at the expense of fill factor, pixel pitch and readout efficiency. In contrast, TDC sharing architecture usually features high fill factor at small pixel pitch and energy efficient event-driven readout. While the photon throughput is not necessarily lower than that of per-pixel TDC architectures, since the throughput is not only decided by the TDC number but also the readout bandwidth. In this paper, a SPAD sensor with 32 × 32 pixels fabricated with a 180 nm CMOS image sensor technology is presented, where dynamically reallocating TDCs were implemented to achieve the same photon throughput as that of per-pixel TDCs. Each 4 TDCs are shared by 32 pixels via a collision detection bus, which enables a fill factor of 28% with a pixel pitch of 28.5 μm. The TDCs were characterized, obtaining the peak-to-peak differential and integral non-linearity of ?0.07/+0.08 LSB and ?0.38/+0.75 LSB, respectively. The sensor was demonstrated in a scanning light-detection-and-ranging (LiDAR) system equipped with an ultra-low power laser, achieving depth imaging up to 10 m at 6 frames/s with a resolution of 64 × 64 with 50 lux background light.
关键词： image sensor,light detection and ranging,time-of-flight,SPAD,time-to-digital converter,LiDAR,single-photon avalanche diode,collision detection bus,dynamic reallocation
更新于2025-09-19 17:15:36
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Design and Analysis of Modified Diode Rectifier Circuit Suitable for Piezoelectric Energy Harvester for Biomedical Applications
摘要： Nowadays renewable energy sources play a significant role in the energy harvesting. For the past decade various energy harvesting methods have been discussed by researchers for capturing the energy from different sources. From the survey, one of the most prominent methods is the use of piezoelectric transducers for harvesting the energy. It is known that piezoelectric energy harvesting is the easiest method of energy harvesting from the various sources available such as human walking, dancing etc. Therefore this method can be implemented in system for wide variety of applications. The piezoelectric transducer AC output is of very low voltage and power and hence insufficient to drive any electrical application. Most of the small scale electrical application generally runs on the DC voltage, therefore the AC voltage obtained from the piezo transducer vibration is rectified using rectifiers to generate DC voltage. Thus in this paper, a modified rectifier AC/DC converter with the combination of an inductor is placed in the rectifier, which enhances the voltage and power from the rectifier output. In order to enhance the voltage rating, a DC/DC converter has been added at the end of a rectifier circuit. From the simulation results the proposed circuit modified rectifier has improved the output voltage as well as output current by 10.19 volts and 0.1019 amps respectively for input voltage of 5V. When compared with conventional rectifier circuit.
关键词： Converter,Energy harvesting,Piezoelectric,Rectifier
更新于2025-09-19 17:15:36
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Experimental investigation and design of sectoral waveguide <i>TM</i> <sub/>01</sub> to <i>TE</i> <sub/>11</sub> mode converter
摘要： In this paper, an all-metal sectoral waveguide (SWG) mode converter has been proposed for TM01 to TE11 mode conversion, suitable for high-power application with high mode conversion efficiency and beam stability. Describing its operating principle, electromagnetic (EM) analysis has been carried out to observe the propagation behaviour in the different structure regions of the mode converter. A comprehensive design methodology, experimental investigation along with its beam stability performance has been presented. This design methodology has been typically demonstrated for 2.9–3.1 GHz frequency device; the performance of the designed device has been carried out using a commercial simulation code. To validate our design methodology and simulation, the results have been compared with experimental results and found in agreement. The proposed SWG mode converter has exhibited high conversion efficiency (98.4%) along with EM beam stability, suiting for the high-power applications.
关键词： mode converter,Sectoral waveguide,high-power microwave,SWG mode converter,HPM mode converter
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Cu-doping Effects in CdSe <sub/>x</sub> Te <sub/>1-x</sub> /CdTe Solar Cells
摘要： Modular multilevel converter (MMC) topology is discussed intensively as a crucial part of future dc grids, especially to integrate offshore wind power. While generalized voltage-source converter models are usually utilized for multiterminal investigations, conclusions on transient dc grid behavior and on ac–dc interactions during distorted ac grid conditions are hard to draw or are limited in their signi?cance. In this paper, a MMC-based dc grid framework with a tripartite focus on an internal converter as well as dc and ac grid control is presented. Besides, an evaluation of the implemented MMC model that incorporates the available arm sum voltage, a decoupled ac and dc current system control concept that is suitable to handle unbalanced voltage conditions is derived for HVDC applications. Combined with wind farm arrays, this collocation allows a meaningful examination of hybrid ACDC structures and the implemented dc grid control methodologies. To provide proof of the universal applicability of this framework, simulations are carried out on a ?ve-terminal system.
关键词： MMC energy balancing,unbalanced operation,wind power integration,HVDC grid control,Generalized modular multilevel converter (MMC) modeling,power converter
更新于2025-09-19 17:13:59