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.
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.
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.
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.
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.
Hyeongwook Lee,Seunghyun Boo,Gunyoung Kim,Bomson Lee 한국전자파학회JEES 2020 Journal of Electromagnetic Engineering and Science Vol.20 No.1
This paper presents a method for solving receiver misalignment (axial or angular) problems in wireless power transfer systems using a multiple-input single-output system. The optimum magnitudes and phases of the transmitter voltages and receiver load for maximum efficiency are derived in convenient analytical forms when negligible mutual couplings between transmitters. These solutions are validated by genetic algorithm optimization and electromagnetic-simulation results for a design ex-ample of two transmitters and one rotating receiver.
A Long-Range UHF-Band Passive RFID Tag IC Based on High-<tex> $Q$</tex> Design Approach
Jong-Wook Lee,Bomson Lee IEEE 2009 IEEE transactions on industrial electronics Vol.56 No.7
<P>We present a fully integrated long-range UHF-band passive radio-frequency-identification tag chip fabricated in 0.35-mum CMOS using titanium (Ti/Al/Ta/Al)-silicon Schottky diodes. The diodes showed low turn-on voltages of 95 and 140 mV for diode currents of 1 and 5 muA, respectively. In addition, the Schottky diodes exhibited low-resistive loss, and a high-<I>Q</I> -factor design approach was exploited to achieve a long read range for the tag integrated circuit (IC). An optimized voltage multiplier resulted in an excellent sensitivity of -14.8 dBm and corresponding power-conversion efficiency of 36.2% for generating an output voltage of 1.5 V at 900 MHz. The range analysis of the measured multiplier performance indicated an operating range of more than 9 m at 4-W Effective Isotropically Radiated Power reader power. The subthreshold-mode operation of an ASK demodulator allowed ultralow power operation. Under power consumption as low as 27 nW, the demodulator supported a data rate of 150 kb/s and a modulation depth of 40%. A new architecture for generating a stable system clock (2.2 MHz) for the tag IC was employed to deal with supply voltage and temperature variations. Measurements showed that the clock generator had an error of 0.91% from the center frequency owing to an 8-b digital calibration scheme.</P>