The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Xun Liu - One of the best experts on this subject based on the ideXlab platform.
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passive radio frequency repeater for enhancing signal reception and transmission in a wireless charging platform
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Kwunchiu Wan, Xun Liu, Quan Xue, S Y HuiAbstract:This paper reports new results of an emerging field that combines radio-frequency (RF) repeater design and wireless power technologies for charging applications. Power electronics-based wireless charging pads have recently been developed for charging portable electronic devices such as mobile phones. However, the Electromagnetic Shield underneath the pad could reduce transmission and reception signals. In this paper, a novel passive RF repeater for a wireless charging platform is proposed and investigated for mitigating the signal blocking problem. Since the effective Shielding structure for the low-frequency charging signal is not RF friendly, the received RF signal of a wireless mobile device can be reduced when the phone is placed on a wireless charging platform. A dual-polarization free-positioning passive RF signal repeater has been successfully designed and implemented. It can improve the RF reception signal strength by at least 3.6 dB without noticeable reduction in energy efficiency in the charging process.
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simulation study and experimental verification of a universal contactless battery charging platform with localized charging features
IEEE Transactions on Power Electronics, 2007Co-Authors: Xun Liu, S Y R HuiAbstract:This paper presents a finite-element (FE) simulation study of a planar contactless battery charging platform for portable consumer electronic equipment. Magnetic field plots of the charging platform are generated under no-load and loaded conditions so that the field distribution of the planar charging platform can be visualized. Three working modes of the platform have been investigated and compared, including full excitation and two forms of selective excitation. With new results arising from this FE simulation study and practical experiments, the theory of the magnetomotive force (mmf) generation of the multilayer planar printed-circuit-board winding array structure can be further understood. The results obtained in this paper provide a foundation of understanding for future design and optimization of planar contactless charging platforms. In addition, it has been confirmed that an Electromagnetic Shield structure that has been applied to coreless planar transformer applications, can work equally well for the planar charging platform.
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an analysis of a double layer Electromagnetic Shield for a universal contactless battery charging platform
Power Electronics Specialists Conference, 2005Co-Authors: Xun Liu, S Y R HuiAbstract:A patented double-layer planar structure is employed to Shield the Electromagnetic (EM) field at the bottom of a universal charging platform. The double-layer consists of a layer of soft ferromagnetic material and a layer of conductive material. Thin 4F1 ferrite plate and the copper sheet are used in this example. This Shielding technique is analyzed with the extended transmission line theory. With the formulas presented, the Shielding effectiveness (SE) of both single-layer Shield and double-layer Shield could be calculated out directly, without using finite-element software. A classical transmitting-receiving loop measurement has been carried out to evaluate the SE of single ferrite Shield, single copper Shield and double-layer Shield respectively. Calculated and measured results in the working frequency range of the charging platform from 100 kHz to 500 kHz confirm that the double-layer Shield has obviously better SE than single-layer Shield and can achieve a SE above 40 dB, which is commonly accepted by the industry. Finally, the potential of this double-layer Shielding technique for a wide range of power electronic applications is discussed
S Y R Hui - One of the best experts on this subject based on the ideXlab platform.
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simulation study and experimental verification of a universal contactless battery charging platform with localized charging features
IEEE Transactions on Power Electronics, 2007Co-Authors: Xun Liu, S Y R HuiAbstract:This paper presents a finite-element (FE) simulation study of a planar contactless battery charging platform for portable consumer electronic equipment. Magnetic field plots of the charging platform are generated under no-load and loaded conditions so that the field distribution of the planar charging platform can be visualized. Three working modes of the platform have been investigated and compared, including full excitation and two forms of selective excitation. With new results arising from this FE simulation study and practical experiments, the theory of the magnetomotive force (mmf) generation of the multilayer planar printed-circuit-board winding array structure can be further understood. The results obtained in this paper provide a foundation of understanding for future design and optimization of planar contactless charging platforms. In addition, it has been confirmed that an Electromagnetic Shield structure that has been applied to coreless planar transformer applications, can work equally well for the planar charging platform.
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an analysis of a double layer Electromagnetic Shield for a universal contactless battery charging platform
Power Electronics Specialists Conference, 2005Co-Authors: Xun Liu, S Y R HuiAbstract:A patented double-layer planar structure is employed to Shield the Electromagnetic (EM) field at the bottom of a universal charging platform. The double-layer consists of a layer of soft ferromagnetic material and a layer of conductive material. Thin 4F1 ferrite plate and the copper sheet are used in this example. This Shielding technique is analyzed with the extended transmission line theory. With the formulas presented, the Shielding effectiveness (SE) of both single-layer Shield and double-layer Shield could be calculated out directly, without using finite-element software. A classical transmitting-receiving loop measurement has been carried out to evaluate the SE of single ferrite Shield, single copper Shield and double-layer Shield respectively. Calculated and measured results in the working frequency range of the charging platform from 100 kHz to 500 kHz confirm that the double-layer Shield has obviously better SE than single-layer Shield and can achieve a SE above 40 dB, which is commonly accepted by the industry. Finally, the potential of this double-layer Shielding technique for a wide range of power electronic applications is discussed
S Y Hui - One of the best experts on this subject based on the ideXlab platform.
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passive radio frequency repeater for enhancing signal reception and transmission in a wireless charging platform
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Kwunchiu Wan, Xun Liu, Quan Xue, S Y HuiAbstract:This paper reports new results of an emerging field that combines radio-frequency (RF) repeater design and wireless power technologies for charging applications. Power electronics-based wireless charging pads have recently been developed for charging portable electronic devices such as mobile phones. However, the Electromagnetic Shield underneath the pad could reduce transmission and reception signals. In this paper, a novel passive RF repeater for a wireless charging platform is proposed and investigated for mitigating the signal blocking problem. Since the effective Shielding structure for the low-frequency charging signal is not RF friendly, the received RF signal of a wireless mobile device can be reduced when the phone is placed on a wireless charging platform. A dual-polarization free-positioning passive RF signal repeater has been successfully designed and implemented. It can improve the RF reception signal strength by at least 3.6 dB without noticeable reduction in energy efficiency in the charging process.
Maria Sabrina Sarto - One of the best experts on this subject based on the ideXlab platform.
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Highly conductive multilayer-graphene paper as a flexible lightweight Electromagnetic Shield
Carbon, 2015Co-Authors: L. Paliotta, S. K. Balijepalli, Alessandra Rinaldi, Saulius Kaciulis, Giovann De Bellis, Francesco Marra, Alessio Tamburrano, Maria Sabrina SartoAbstract:A graphene-based porous paper made of multilayer graphene (MLG) microsheets is developed for application as a flexible electrically conducting Shielding material at radio frequency. The production process is based on the thermal expansion of a graphite intercalated compound, the successive liquid-phase exfoliation of the resulting expanded graphite in a proper solvent, and finally the vacuum filtration of the MLG-suspension using a nanoporous alumina membrane. Enhancement of the electrical conductivity and Electromagnetic Shielding properties of the MLG paper is achieved by gentle annealing at 250 °C overnight, and by mechanical compression at 5 MPa. The obtained results show that the developed MLG papers are characterized by an electrical conductivity up to 1443.2 S/cm, porosity around 43%, high flexibility, Shielding effectiveness up to 55 dB at 18 GHz with a thickness of 18 μm. Numerical simulations are performed in order to understand the main factors contributing to the Shielding performance of the new material.
Kwunchiu Wan - One of the best experts on this subject based on the ideXlab platform.
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passive radio frequency repeater for enhancing signal reception and transmission in a wireless charging platform
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Kwunchiu Wan, Xun Liu, Quan Xue, S Y HuiAbstract:This paper reports new results of an emerging field that combines radio-frequency (RF) repeater design and wireless power technologies for charging applications. Power electronics-based wireless charging pads have recently been developed for charging portable electronic devices such as mobile phones. However, the Electromagnetic Shield underneath the pad could reduce transmission and reception signals. In this paper, a novel passive RF repeater for a wireless charging platform is proposed and investigated for mitigating the signal blocking problem. Since the effective Shielding structure for the low-frequency charging signal is not RF friendly, the received RF signal of a wireless mobile device can be reduced when the phone is placed on a wireless charging platform. A dual-polarization free-positioning passive RF signal repeater has been successfully designed and implemented. It can improve the RF reception signal strength by at least 3.6 dB without noticeable reduction in energy efficiency in the charging process.