• 조명전기설비학회논문지
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• 제28권11호
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• pp.33-41
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• 2014

This paper is research result for a development of sapphire silicon ingot glowing(SSIG) PWM converter system for 80kW 10kA. The system include 3-phase AC-DC diode rectifier of input voltage AC 380V and 60Hz, DC-AC single phase full bridge PWM inverter of high frequency, AC-DC single-phase full wave rectifier using center-tapped of transformer for low voltage 8.0V and large current 10,000A of output specification, tungsten resistor load 0.1[$m{\Omega}$]. PWM switching frequency for IGBT inverter control set 30kHz. The suggested researching contents are designed data sheets of power converter system, PSIM simulation, operating characteristics and analysis results of developed SSIG system. This paper propose

• 반도체디스플레이기술학회지
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• 제12권2호
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• pp.63-66
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• 2013

Carbon Nanotube have been proposed for use in various applications for electromechanical systems. Nano-electromechanical resonators which provide high frequency resolution and long energy storage time, play an important role in wide area fields of science and engineering. Using the control of tension in carbon nanotube, can be made the tunable resonator. In the study, we analysis the tunable frequency change of resonator by tension changes due to the rotation angles of the single-walled carbon nanotube resonator. The frequency characteristics of a resonator as a function of the rotation angle. The tension was found to decrease with increasing rotation angle, and therefore the resonance frequencies could be changed by controlling the single-walled carbon nanotube rotation angle. The resonance frequencies decreased with increasing angle, and when the rotation angle was greater than $60^{\circ}$, these changes were marked.

• Journal of electromagnetic engineering and science
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• 제14권3호
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• pp.306-313
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• 2014

A Fabry-Perot resonator cavity antenna for Ku-band application is presented in this paper. The Fabry-Perot cavity is formed by a ground plane and a frequency selective surface (FSS) made of a circular hole array. The cavity resonance is excited by a single-feed microstrip patch located inside the cavity. The measured results show that the proposed antenna has an impedance bandwidth of approximately 13% ($VSWR{\leq}2$) and a 3-dB gain bandwidth of approximately 7%. The antenna produces a maximum gain of 18.5 dBi and good radiation patterns over the entire 3-dB gain bandwidth. The antenna's very thin profile, high directivity, and single excitation feed make it promising for use in wireless and satellite communication applications in a Ku-band frequency.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1280-1285
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• 2017

In this paper, we consider iterative soft-decision feedback equalizers (sDFE), a.k.a. turbo equalizers for single-carrier transmission. Turbo equalizer takes log-likelihood ratio (LLR) feedback from channel decoder and convert the LLR into symbol estimates and variances to be used for the LLR update at the sDFE. Specifically, we consider both time domain and frequency-domain sDFE and compare their performances. The results shows that frequency-domain sDFE performs better than time-domain one and also that considerable gain can be obtained especially when the channel has deep nulls.

• Journal of information and communication convergence engineering
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• 제13권2호
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• pp.69-73
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• 2015

We focus on a sounding signal design for single-input single-output orthogonal frequency division multiplexing (SISO-OFDM) systems. We show that the frequency spectrum of an optimum sounding signal has a constant magnitude across the frequency band for the cases with or without Doppler effects. Simulation results show that the designed optimum sounding signal outperforms random sounding signals and that the performance of a maximal-length shift register sequence is indistinguishable from that of the optimum sounding signal.

• Journal of Information Processing Systems
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• 제11권3호
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• pp.342-353
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• 2015

It is widely accepted that single carrier frequency division multiple access (SC-FDMA) is an excellent candidate for broadband wireless systems. Channel estimation is one of the key challenges in SC-FDMA, since accurate channel estimation can significantly improve equalization at the receiver and, consequently, enhance the communication performances. In this paper, we study the application of compressive sensing for sparse channel estimation in a SC-FDMA system. By skillfully designing pilots, their patterns, and taking advantages of the sparsity of the channel impulse response, the proposed system realizes channel estimation at a low cost. Simulation results show that it can achieve significantly improved performance in a frequency selective fading sparse channel with fewer pilots.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1134-1135
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• 2007

In this paper, we proposed the isolated multi-level inverter using 3-phase transformers. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformer could be reduced comparing with an exiting 3-phase multi-level inverter using single phase transformer. Also, using phase angle control method with switching frequency equal to output fundamental frequency, harmonics component of output voltage and switching losses can be reduced. Finally, we made a prototype inverter to clarify the proposed electric circuit and reasonableness of control signal.

• Computers and Concrete
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• 제32권3호
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• pp.303-311
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• 2023

An analysis of the Poisson's ratios influence of single walled carbon nanotubes (SWCNTs) based on Sander's shell theory is carried out. The effect of Poisson's ratio, boundary conditions and different armchairs SWCNTs is discussed and studied. The Galerkin's method is applied to get the eigen values in matrix form. The obtained results shows that, the decrease in ratios of Poisson, the frequency increases. Poisson's ratio directly measures the deformation in the material. A high Poisson's ratio denotes that the material exhibits large elastic deformation. Due to these deformation frequencies of carbon nanotubes increases. The frequency value increases with the increase of indices of single walled carbon nanotubes. The prescribe boundary conditions used are simply supported and clamped simply supported. The Timoshenko beam model is used to compare the results. The present method should serve as bench mark results for agreeing the results of other models, with slightly different value of the natural frequencies.

• 전자공학회논문지
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• 제52권2호
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• pp.7-17
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• 2015

본 논문에서는 터보 등화기를 결합한 단일 안테나 구조의 동일 대역 동시 전 이중 통신 시스템을 제안한다. 본 논문에서 제안하는 시스템은 단일 안테나를 사용하기 위하여 Balanced Feed Network회로를 이용하여 송신 신호와 수신 신호를 격리시킨다. 또한 추가적으로 자기 간섭 신호를 감쇄시키기 위하여 RF Cancellation과 Digital Cancellation을 사용한다. 마지막으로 상대국에서 자국으로의 채널 상황이 열악할 경우와 Digital Cancellation이후에도 남은 잔류 자기 간섭 신호에 의한 상대국에서 보낸 수신 신호에 오류가 발생할 경우에도 통신의 신뢰도를 보장할 수 있도록 터보 등화기를 결합한다. 본 논문에서 제안하는 시스템의 성능을 확인하기 위하여 Simulink 시뮬레이션 프로그램을 이용하여 시스템을 설계하였다. 시뮬레이션 결과, 본 논문에서 제안하는 시스템은 단일 안테나를 사용하며 동일 대역에서 Balanced Feed Network, RF(radio frequency) Cancellation, Digital Cancellation 그리고 터보 등화기를 통해 자기 간섭 신호를 효과적으로 제거하고 열악한 채널 상황에서도 전 이중통신을 할 수 있다.

• 한국정보통신학회논문지
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• 제8권3호
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• pp.570-576
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• 2004

본 논문에서는 고속 무선 LAN에서 사용하는 IEEE 802.11a OFDM(Orthogonal Frequency Division Multiplexing)에서 주요 구성인 IFFT/FFT(Inverse Fast Fourier Transform/Fast Fourier Transform)에 대한 설계에 대해 비교하였다. 설계된 IFFT/FFT는 무선 LAN의 표준에 맞게 64 point의 FFT로 연산을 수행하며, S/P(Serial-to-Parallel)이나 P/S(Parallel-to-Serial)변환기가 필요 없는 Pipelined FFT의 구조로 설계하였다. 그 중 Radix-2 알고리즘을 이용한 R22SDF(Radix-2 Single-path Delay Feedback) 방식, R2SDF(Radix-2 Single-path Delay Feedback) 방식과 Radix-4 알고리즘을 이용한 R4SDF(Radix-4 Single-path Delay Feedback) 방식, R4SDC(Radix-4 Single-path Delay Commutator) 방식을 사용하여 비교하였다. 하드웨어 구현 시 발생하는 오차를 줄이기 위해 Butterfly 연산 후 일부 소수점을 가지고 계산하는 구조로 설계하였다. R22SDF 방식을 이용할 경우 메모리를 제외한 전체 게이트 수가 44,747 개로 다른 구조에 비해 적은 하드웨어와 낮은 오차율을 가진다.