http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Synthesis of Bulk Medium with Negative Permeability Using Ring Resonators
Bomson Lee,Gunyoung Kim 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.2
This paper presents simple expressions for the effective permeability of bulk metamaterial consisting of ring resonators (RRs) or split ring resonators (SRRs) based on the convenient geometrical factors of the structure compared with wavelength. The resonant frequency dependence of the medium permeability, including loss effects, is analyzed in detail. Inverting the analysis equations, useful design (or synthesis) equations are derived for a systematic design process with some examples. This paper may particularly be useful for the design of a bulk metamaterial with a specific negative relative permeability at a desired frequency. The loss of metamaterials consisting of RRs (or SRRs) is also analyzed over a wide frequency band from 10 MHz to 10 THz.
Bomson Lee,Gunyoung Kim 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.2
Alternative analytic expressions for the mutual inductance (Lm) and coupling coefficient (k) between circular loops are presented using more familiar and convenient expressions that represent the property of reciprocity clearly. In particular, the coupling coefficients are expressed in terms of structural dimensions normalized to a geometric mean of radii of two loops. Based on the presented expressions, various aspects of the mutual inductances and coupling coefficients, including the regions of positive, zero, and negative value, are examined with respect to their impacts on the efficiency of wireless power transmission.
Analysis of Efficiencies for Multiple-Input Multiple-Output Wireless Power Transfer Systems
Bomson Lee,Sejin Kim 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.2
Wireless power transfer (WPT) efficiencies for multiple-input multiple-output (MIMO) systems are formulated with a goal of achieving their maximums using Z matrices. The maximum efficiencies for any arbitrarily given configurations are obtained using optimum loads, which can be determined numerically through adequate optimization procedures in general. For some simpler special cases (single-input single-output, single-input multiple-output, and multiple-input single-output) of the MIMO systems, the efficiencies and optimum loads to maximize them can be obtained using closed-form expressions. These closed-form solutions give us more physical insight into the given WPT problem. These efficiencies are evaluated theoretically based on the presented formulation and also verified with comparisons with circuit- and EM-simulation results. They are shown to lead to a good agreement. This work may be useful for construction of the wireless Internet of Things, especially employed with energy autonomy.
Design of Thin RC Absorbers Using a Silver Nanowire Resistive Screen
Bomson Lee,Junho Lee 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.2
A resistive and capacitive (RC) microwave absorber with a layer thickness less than a quarter of a wavelength is investigated based on closed-form design equations, which are derived from the equivalent circuit of the RC absorber. The RC absorber is shown to have a theoretical 90% absorption bandwidth of 93% when the electrical layer thickness is 57° (about λ₀/6). The trade-offs between the layer thickness and the absorption bandwidth are also elucidated. The presented formulation is validated by a design example at 3 GHz. The RC absorber is realized using a silver nanowire resistive rectangular structure with surrounding gaps. The measured 90% absorption bandwidth with a layer thickness of λ₀/8 is 76% from 2.3 GHz to 5.1 GHz in accordance with the theory and EM simulations. The presented design methodology is scalable to other frequencies.
Simplified Modeling of Ring Resonators and Split Ring Resonators Using Magnetization
Dongho Jeon,Bomson Lee 한국전자파학회JEES 2013 Journal of Electromagnetic Engineering and Science Vol.13 No.2
This paper examines various aspects of the electromagnetic responses of the ring resonator located in the transverse electromagnetic cell. In addition, an equivalent circuit for the ring resonator is proposed and analyzed based on the electromagnetic phenomenon of the resonator. The equivalent circuit was simply modeled based on the concept of magnetization. A method for achieving a wider operating bandwidth of the negative permeability is provided. The ring resonator with its resonant frequency of 13.56 ㎒ was designed and its characteristics were examined in terms of S-parameters, effective permeability, loss rate, bandwidth, etc. The circuit and electromagnetic simulation results show an excellent agreement as well as that of theory.
Analysis of Magnetically Coupled Wireless Power Transmission for Maximum Efficiency
Chungju Kim,Bomson Lee 한국전자파학회JEES 2011 Journal of Electromagnetic Engineering and Science Vol.11 No.3
We have proposed and analyzed an equivalent circuit for a magnetically coupled wireless power transmission (WPT) system between two loop resonators by considering its coupling coefficient and radiation-related parameters. A complete formulation is provided for all the necessary circuit parameters. The mechanism of radiation loss is sufficiently explained. The circuit and electromagnetic (EM) simulation results have been shown to be in good agreement. Based on the proposed circuit formulation, a specific load impedance for maximum WPT efficiency was found to exist. The proposed modeling of the WPT in terms of circuit characterizations provides sufficient insight into the problems associated with WPT.
Design of Wideband Microwave Absorbers Using Reactive Salisbury Screens with Maximum Flat Reflection
Sanghoek Kim,Bomson Lee,Gunyoung Kim 한국전자파학회JEES 2019 Journal of Electromagnetic Engineering and Science Vol.19 No.2
This paper presents a design methodology for wideband single-layered microwave absorbers with arbitrary absorption at the design center frequency using reactive Salisbury screens. The bandwidth of the absorber increases when the flatness of the reflection response at the design center frequency is maximized. Based on this observation, closed-form design formulas for wideband absorbers are derived. As they are scalable to any design frequency, wideband reactive screens can be systematically realized using two-dimensional periodic crossed-dipole structures patterned on a resistive sheet. Based on this method, a single-layered absorber with a 90% bandwidth improved to 124% of the design center frequency is presented. For the purpose of physical demonstration, an absorber with a design center frequency of 10 ㎓ is designed and fabricated using a silver nanowire resistive film with a surface resistance of 30 Ω/square. The measured absorption shows a good agreement with both the calculation and the electromagnetic simulation.
Digitally-Controlled Bondwire Inductor with High Quality Factor and Wide Tuning Range
Yonggoo Lee,Bomson Lee 한국전자파학회JEES 2020 Journal of Electromagnetic Engineering and Science Vol.20 No.3
A tunable bondwire inductor (TBI) with high-quality factor and wide tuning range is presented. The proposed TBI is fabricated on a single chip by combining a single-pole four-throw (SP4T) switch integrated circuit (IC) and four bondwire inductors on a package substrate. The SP4T switch IC is fabricated using 180 nm silicon-on-insulator (SOI) complementary metal-oxide-semiconductor (CMOS) technology. The fabricated TBI chip exhibits a 521% tuning range of inductance from 1.77 to 11 nH at 0.1 GHz and a relatively highquality factor. To the knowledge of the authors, the results of this work demonstrate the best combined performance of inductance tuning range and quality factor.