10,353 research outputs found
A survey of electromagnetic influence on uavs from an ehv power converter stations and possible countermeasures
National Natural Science Foundation of China (Grant Nos. 11872148, U1908217, 61801034).It is inevitable that high-intensity, wide-spectrum electromagnetic emissions are generated by the power electronic equipment of the Extra High Voltage (EHV) power converter station. The surveillance flight of Unmanned Aerial Vehicles (UAVs) is thus, situated in a complex electromagnetic environment. The ubiquitous electromagnetic interference demands higher electromagnetic protection requirements from the UAV construction and operation. This article is related to the UAVs patrol inspections of the power line in the vicinity of the EHV converter station. The article analyzes the electromagnetic interference characteristics of the converter station equipment in the surrounding space and the impact of the electromagnetic emission on the communication circuits of the UAV. The anti-electromagnetic interference countermeasures strive to eliminate or reduce the threats of electromagnetic emissions on the UAVâs hardware and its communication network.publishersversionpublishe
An EMI characterization and modeling study for consumer electronics and integrated circuits
âAs internet-of-things (IoT) applications surge, wireless connectivity becomes an essential part of the network. Smart home, one of the most promising application scenarios of IoT, will improve our life quality enormously. However, electromagnetic interference (EMI) to the receiving antenna, either from another electronic product or from a module/an integrated circuit(IC) inside the same wireless device, will degrade the performance of wireless connectivity, thus influencing the user experience. Characterization and modeling of the EMI become increasingly important.
In the first part, an improved method to extract equivalent dipoles from magnitude- only electromagnetic-field data based on the genetic algorithm and back-and-forth iteration algorithm is proposed. The method provides an automatic flow to extract the equivalent dipoles from electromagnetic-field data on arbitrarily shaped scanning surfaces and minimizes the number of extracted dipoles. In the second part, both the differential mode (DM) and common mode (CM) EMI below 1 MHz from the ac-dc power supply in a LED TV is analyzed and modeled. Through joint time-frequency analysis, the drain-to-source voltage of the power MOSFET in the power factor correction (PFC) converter is identified as the dominant noise source of both CM and DM EMI below 1 MHz from the power supply. The current paths of DM and CM EMI are explained and modeled by a linear equivalent circuit model. In the last part, the noise source and current path of the conducted CM EMI noise from a Qi-compliant wireless power transfer (WPT) system for mobile applications are analyzed. The analysis and modeling explain the mechanism of the CM EMI noise and provide guidelines to reduce the CM EMI noiseâ--Abstract, page iv
Implementing Pseudo-Random Control in Boost Converter: An Effective Approach for Mitigating Conducted Electromagnetic Emissions
Currently, pulse width modulation (PWM) is a prevalent technique in the field of DC-DC converter control. Its primary objectives encompass maintaining the regulation of the converter's output voltage and improving the load's performance by mitigating the adverse effects caused by harmonic distortions. Unfortunately, the utilization of PWM is associated with significant levels of residual harmonics, characterized by notable amplitudes and frequencies, which have the potential to induce mechanical vibrations, acoustic disturbances, and electromagnetic interference (EMI).To address this challenge, a method known as pseudo-random modulation (PRM) has been developed. In comparison to traditional PWM, PRM offers ease of implementation and high efficacy in EMI mitigation. PRM achieves this by distributing harmonic power across a broader frequency range, thereby reducing the prominence of high-amplitude harmonics at specific frequencies. Within the context of Spread Spectrum Modulation (SSM), this study extensively explores diverse converter topologies and proposes an innovative hardware implementation using the cost-effective Atmega328p microcontroller. Furthermore, the study scrutinizes the consequences of implementing this randomized control strategy to reduce electromagnetic emissions from a Boost converter, a well-recognized source of significant interference in its operational environment. Ultimately, the aim is to evaluate the effectiveness of these applied methodologies in achieving the maximum dispersion of the power spectrum, thereby enhancing overall electromagnetic compatibility
EMI measurement and modeling techniques for complex electronic circuits and modules
This dissertation consists of four papers. In the first paper, a combined model for predicting the most critical radiated emissions and total radiated power due to the display signals in a TV by incorporating the main processing board using the Huygens Equivalence theorem and the radiation due to the flex cable based on active probe measurements was developed.
In the second paper, a frequency-tunable resonant magnetic field probe was designed in the frequency range 900-2260 MHz for near-field scanning applications for the radio frequency interference studies by using a varactor diode providing the required capacitance and the parasitic inductance of a magnetic field loop (i.e., a parallel LC circuit). Measurement results showed good agreement with the simulated results.
In the third paper, a wideband microwave method was developed as a means for rapid detection of slight dissimilarities (including counterfeit) and aging effects in integrated circuits (ICs) based on measuring the complex reflection coefficient of an IC when illuminated with an open-ended rectangular waveguide probe, at K-band (18-26.5 GHz) and Ka-band (26.5-40 GHz) microwave frequencies.
In the fourth paper, a method to predict radiated emissions from DC-DC converters with cables attached on the input side to a LISN and on the output side to a DC brushless motor as load based on linear terminal equivalent circuit modeling was demonstrated. The linear terminal equivalent model was extracted using measured input and output side common mode currents for various characterization impedances connected at the input and output terminals of the converter --Abstract, page iv
Kompetensi guru dalam pengajaran amali reka bentuk dan teknologi di Sekolah Rendah Daerah Batu Pahat
Kompetensi bermaksud kemampuan atau kecekapan seseorang individu dalam
melakukan sesuatu tugasan. Kompetensi juga merujuk kepada kemampuan
seseorang dalam melaksanakan sesuatu yang diperolehi melalui pendidikan dan
juga merujuk kepada prestasi dan perbuatan yang rasional untuk memenuhi
spesifikasi tertentu di dalam pelaksanaan tugas-tugas pendidikan. Objektif
kajian ini dijalankan adalah untuk mengenalpasti tahap kompetensi guru
terhadap pengajaran amali Reka Bentuk dan Teknologi di Sekolah Rendah
Daerah Batu Pahat. Kajian ini berbentuk tinjauan deskriptif yang menggunakan
borang soal selidik sebagai instrumen kajian. Borang soal selidik yang dibina
adalah berdasarkan kepada tiga elemen iaitu elemen pengetahuan, kemahiran
dan sikap. Seramai 118 orang guru yang mengajar mata pelajaran ini telah
terlibat sebagai responden. Data yang dikumpulkan telah dianalisis dengan
menggunakan perisian Statistical Package for Social Science (SPSS) versi 19
yang melibatkan statistik skor min dan ujian-T tidak bersandar. Hasil dapatan
kajian yang diperolehi menunjukkan guru-guru Reka Bentuk dan Teknoogi
mempunyai tahap kompetensi yang tinggi terhadap proses pengajaran amali
iaitu skor min yang diperolehi pada elemen pengetahuan adalah 4.23, elemen
kemahiran adalah 4.30, dan elemen sikap adalah 4.47. Dapatan kajian juga
menunjukkan tidak terdapat perbezaan yang signifikan terhadap tahap
kompetensi berdasarkan jantina guru lelaki dan guru perempuan dengan nilai
sigifikan melebihi 0.05 iaitu sebanyak 0.059. Beberapa cadangan untuk
penambahbaikan juga dikemukan dalam kajian ini. Hasil dari dapatan kajian ini
dapat digunakan sebagai cadangan garis panduan kepada guru-guru Reka
Bentuk dan Teknologi untuk mencapai Standard Kompetensi Guru
Simple modeling for conducted common-mode current in switching circuits
Common mode current strongly depends on stray capacitance of each circuit node, especially those with high dv/dt and di/dt. To build a simple model for conducted common mode current in switching circuit a computer software based on Partial Element Equivalent Circuit (PEEC) method is used to calculate the parasitic elements of the printed circuit board (PCB). Simulation results agree well with experimental results up to 10 MHz.published_or_final_versio
EMI due to electric field coupling on PCB
In switching converter circuits, EM noise can couple between PCB traces through the effect of electric field coupling. An experiment using a flyback converter verifies the severity of this effect. Further experiments and field plots confirm that a good PCB layout can significantly reduce conducted EMI due to unintentional E-field coupling.published_or_final_versio
Essential-coupling-path models for non-contact EMI in switching power converters using lumped circuit elements
This paper proposes a simple lumped circuit modeling approach for describing noncontact EMI coupling mechanisms in switching power converters. The resulting model assumes a minimum number of noise sources and contains essential coupling paths that allow easy physical interpretations. Essentially, all capacitive couplings are represented by an equivalent noise voltage source and six coupling impedances, whereas all inductive couplings are represented by an equivalent noise current source and three coupling impedances. The resulting coupled noise appears as currents flowing into the terminals of the Line-Impedance-Stabilization-Network (LISN). The equivalent voltage source can be conveniently approximated as the switching-node-to-zero voltage, which is typically a rectangular pulse of a few hundred volts. The equivalent current source can be modeled as the current flowing around a loop containing the equivalent voltage source and parasitics such as winding capacitance of the power transformer, the snubber capacitance and connection inductances. Also, the coupling impedances can be estimated by making simplifying assumptions about the geometry of the components and tracks, or by direct measurements. Simulations and experiments verify how inductive and capacitive couplings through each path may produce substantial EMI measured by the LISN. Being based on a lumped circuit approach, the proposed model is easy to apply in practice for understanding, diagnosing and approximating EMI behaviors.published_or_final_versio
Essential-coupling-path models for non-contact EMI in switching power converters using lumped circuit elements
Author name used in this publication: Chi K. TseAuthor name used in this publication: C. P. Liu2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
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