• 한국군사과학기술학회지
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• 제20권5호
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• pp.673-680
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• 2017

In the proposed paper, we designed low noise frequency synthesizer with compact size for Multi-Band. The proposed frequency synthesizer consists of fundamental frequency band(2 GHz) and harmonic frequency band(4 GHz). To improve the phase noise and spurious level of frequency synthesizer, we analyze how the configuration of frequency synthesizer affect the phase noise and design the multi-band's structure. The implemented frequency synthesizer reduce both the phase noise and spurious level. The phase noise is -92.17 dBc/Hz at 1 kHz frequency offset in 2 GHz and -90.50 dBc/Hz at 1 kHz frequency offset in 4 GHz. All spurious signals including fundamental frequency are suppressed at least 20 dBc than the second harmonic frequency.

• 한국위성정보통신학회논문지
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• 제6권1호
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• pp.45-49
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• 2011

본 논문에서 위성통신 단말에 적용할 PLL 주파수 합성기의 잡음 특성을 분석하였고, 주파수 간격(step size)을 작게하면서 저 위상잡음 특성을 갖도록 설계 및 구현하였다. 구현된 주파수 합성기 모듈은 950~1450 MHz 대역에서 -2dBm 이상의 출력을 보였으며, 위상잡음은 10kHz offset에서 -101dBc/Hz로 측정되었다. 주파수 합성기의 위상잡음 특성을 분석한 결과 루프대역 내에서의 위상잡음은 분주기 값을 작게 하기위한 LO의 특성을 따라 감을 알 수 있었다.

• 전자공학회논문지
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• 제50권1호
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• pp.97-101
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• 2013

There is a growing need for optical communication systems that convert large volumes of data to optical signals and that accommodate and transmit the signals across long distances. Digital optical communication consists of a master unit (MU) and a slave unit (SU). The MU transmits data to SU using digital optical signals. However, digital optical units that are commercially available or are under development transmit data using two's complement representation. At low input levels, a large number of SSOs (simultaneous switching outputs) are required because of the high rate of bit switching in two's complement, which thereby increases the power noise. This problem reduces the overall system capability because a DSP (digital signal processor) chip (FPGA, CPLD, etc.) cannot be used efficiently and power noise increases. This paper proposes a change from two's complement to a more efficient method that produces less SSO noise and can be applied to existing digital optical units.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.46-50
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• 1997

Acoustic signals from the vehicle muffler has various kinds of noises. For control of noise from the vehicle muffler, the major part of noise to be contorted is that correlated with the revolution of the vehicle engine. For this reason the most efficient method for noise control is to use the extracted acoustic signals correlated with revolution as a controlled factor. Therebefore in this paper we developed and proofed an algorithm for efficient amplitude detection and phase detection related to the engine operating revolution from the vehicle muffler noise by orthogonality.

• 한국군사과학기술학회지
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• 제17권5호
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• pp.629-636
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• 2014

In the proposed paper, we designed low phase noise frequency synthesizer for Ku-band. The proposed up-mixing frequency synthesizer consists of narrow local oscillation part and variable frequency oscillation part. To improve the phase noise of frequency synthesizer, we analyze how the configuration of frequency synthesizer affect the phase noise. The implemented frequency synthesizer reduce the phase noise. The phase noise is -95.18dBc/Hz at 7kHz frequency offset in 16GHz and -94.27dBc/Hz at 7kHz frequency offset in 16.125GHz.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.115-119
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• 2011

Instead of very expensive sound record and professional measurement microphones the low cost Surface Mounted Device (SMD) microphones are proposed for practical barrier ANC system. FRF of the microphones and theirs sensitivity to the wind interferences are evaluated in semi anechoic chamber. The improvement of feedforward algorithm noise reduction index was evaluated based on measured coherence function between tested SMD and reference microphone. Test was performed at various wind speed from 1 m/s to 5 m/s.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.636-642
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• 1997

Laminar vortex shedding behind a circular cylinder with and without splitter plates attached to the circular cylinder at low Reynolds numbers are simulated by solving the unsteady incompressible Navier-Strokes equations. The Strouhal number, lift and drag rapidly change with the splitter plate. Far-field noise from the vortex shedding behind the cylinder is computed using the Lighthill acoustic analogy and the Curle's solution for the Lighthill equation. The acoustic source functions are obtained from the computed near-field velocity and pressure. Numerical results show that the volume quadrupole noise is small at low Mach numbers, compared with the surface dipole noise. Also the amplitude and frequency of the acoustic density fluctuations are varied with the length of splitter plates. The scattering effects at the edge of a splitter plate are considered by using the half-plane Green's function.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1343-1348
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• 2014

The low frequency noise in Silicon Nanowire Field Effect Transistors is analyzed by characterizing the gate electrode dependence on various geometrical parameters. It shows that gate electrodes have a strong impact in the flicker noise of Silicon Nanowire Field effect transistors. Optimization of gate electrode was done by comparing different performance metrics such a DIBL, SS, $I_{on}/I_{off}$ and fringing capacitance using TCAD simulations. Molybdenum based gate electrode showed significant improvement in terms of high drive current, Low DIBL and high $I_{on}/I_{off}$. The noise power sepctral density is reduced by characterizing the device at higher frequencies. Silicon Nanowire with Si3N4 spacer decreases the drain current spectral density which interms reduces the fringing fields there by decreasing the flicker noise.

• 한국항공우주학회지
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• 제43권6호
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• pp.516-525
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• 2015

본 연구에서는 정지 비행과 저속 하강 비행하는 회전익기 로터에 대한 소음을 예측하고 실험값과 비교하여 검증하였다. Ffowcs Williams-Hawkings 방정식을 이용한 소음압 예측 프로그램을 개발하였다. 해석 결과의 검증을 위해서 2가지 풍동 시험 결과를 이용하였다. Boeing 360 모델 로터를 이용하여 정지 비행 조건에서의 저차 주파수 대역의 소음압을 검증하였고, HART II 로터를 이용하여 저속 하강 비행 조건의 중간 주파수 대역의 BVI 소음을 검증하였다. 하중 소음을 예측하기 위해서 정지비행 조건에서는 자유후류기법을 통한 공력계수를 이용하였고, 저속 하강 비행 조건에서는 CFD/CSD 연계해석 결과를 이용하였다. 소음해석 결과 저차 주파수 대역의 소음압과 중간 주파수 대역의 BVI 소음압을 비교적 잘 예측하는 것을 확인하였다. BVI 소음압은 FFT 해석을 통하여 소음 방사 지도를 그려 실험결과와 비교하였다. 비교 결과 시험결과와 비교적 유사하게 예측하는 것을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1842-1847
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• 2000

In this paper, a review is attempted for understanding of aeolian noise from high voltage insulators and their aerodynamic noise characteristics were investigated using the low noise wind tunnel. The noise from the insulators was dependent upon the wind speed and their orientation relative to the wind direction. The noise spectrum revealed sharp peak which was found the cavity resonance frequency.