• Ocean and Polar Research
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• 제29권4호
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• pp.311-316
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• 2007

Ocean noise may be used for monitoring wind speed and rainfall rate on the sea surface, as well as for tracking whales' migration routes. In particular, low-frequency ocean noise has recently been of concern with relation to the behavior of marine mammals. Low-frequency ocean noise has been increasing over the past few decades due to increase of ship traffic and offshore oil industry activities. Mechanical noise such as flow noise and cable strumming noise may be induced if low-frequency ocean noise is measured by cabled traditional hydrophone in high current areas. To successfully measure low-frequency ocean noise in a shallow water environment with strong current, we developed a self-recording hydrophone. This paper describes the main configurations of the self-recording hydrophone and presents some results on measured data.

• 한국소음진동공학회논문집
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• 제25권7호
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• pp.470-480
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• 2015

As the railway noise guideline of the Ministry of Environment after 2017 is strictly enforced, the noise level at stationary condition of urban railway is demanding the reduction about 2 dB(A). And the noise level at running condition is reduced by 6 dB(A) at 80 km/h. Therefore, the devices that causes noise shall arrange for the improvement plan of noise reduction for each device. In this paper, we carried out a technical review of the driving gear used to drive the vehicle from a variety of noise-induced equipment of a urban railway. Analyze the causes of the current noise levels and noise cause about the driving gear used in current urban railway and this study analyzes the noise level and noise cause the drive gear being used in the current urban railway. Finally, in this paper proposes a scheme for reducing the noise that can be designed to reduce the noise with considering the noise cause analysis.

• Journal of Multimedia Information System
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• 제5권2호
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• pp.139-142
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• 2018

This work presents a novel architecture of phase locked loop (PLL) with the current compensating scheme to improve phase noise characteristic. The proposed PLL has two charge pumps (CP), main-CP (MCP) and sub-CP (SCP). The smaller SCP current with same time duration but opposite direction of UP/DN MCP current is injected to the loop filter (LF). It suppresses the voltage fluctuation of LF. The PLL has a novel voltage controlled oscillator (VCO) consisting of a voltage controlled resistor (VCR) and the three-stage ring oscillator with latch type delay cells. The VCR linearly converts voltage into current, and the latch type delay cell has short active on-time of transistors. As a result, it improves phase noise characteristic. The proposed PLL has been fabricated with $0.35{\mu}m$ 3.3 V CMOS process. Measured phase noise at 1 MHz offset is -103 dBc/Hz resulting in 3 dBc/Hz phase noise improvement compared to the conventional PLL.

• 한국음향학회지
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• 제31권8호
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• pp.523-531
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• 2012

최근 친 환경 발전에 관한 관심이 높아지면서 태양광, 풍력, 조력, 조류 발전에 대한 수요가 점차 증가되고 있다. 이러한 친 환경 발전 방식 중 조석운동에 의한 해수의 흐름을 이용하는 조류발전은 지형적 특성에 의해 강한 조류가 발생하는 지역에서만 사용할 수 있는 특수한 발전 방식이다. 울돌목 해역은 조류 발전이 가능한 매우 강한 조류가 형성되는 지역으로 다른 지역의 해역과 구분되는 특별한 환경을 제공한다. 하지만, 해양에서의 인간의 활동은 수중소음을 야기하여 해양환경에 큰 영향을 미친다. 최근에는 환경영향평가의 중요성이 대두되면서 발전소 가동 시의 소음 특성 분석 및 전파양상 예측에 대한 필요성이 증가하고 있다. 본 연구는 조류발전소의 수중소음 특성을 측정하고 울돌목 해역으로의 전파양상을 모델링 하였다.

• 한국정밀공학회지
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• 제17권1호
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• pp.101-109
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• 2000

Mutual torque ripple in a brushless DC motor is the main source of acoustic noise, especially fur motor operation with high speed and torque. This paper presents a method to obtain mutual torque ripple to identify acoustic noise source. Mutual torque ripple can be determined by analyzing phase current shape and magnetic circuit with different lead angles. Current shape is determined by state space model of voltage equation with the use of inductance calculated by FEM, and confirmed by experimental results. Mutual torque ripple is also determined by FEM analysis for the calculated current shape. Acoustic noise experiment reveals that mutual torque ripple with different lead angle is one of the main sources for noise generation in a brushless DC motor.

• 반도체디스플레이기술학회지
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• 제19권3호
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• pp.73-76
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• 2020

The physics-based compact gate leakage current noise models in nanoscale MOSFETs are developed in such a way that the models incorporate important physical effects and are suitable for circuit simulators, including QM (quantum-mechanical) effects. An emphasis on the trap-related parameters of noise models is laid to make the models adaptable to the variations in different process technologies and to make its parameters easily extractable from measured data. With the help of an accurate and generally applicable compact noise models, the compact noise models are successfully implemented into BSIM (Berkeley Short-channel IGFET Model) format. It is shown that the noise models have good agreement with measurements over the frequency, gate-source and drain-source bias ranges.

• 전기학회논문지
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• 제58권2호
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• pp.363-368
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• 2009

In the paper, we confirmed improvement Noise figure of the entire RF front-end using spiral inductor with PGS(Patterned Ground Shield) and current bleeding techniques. LNA design is to achieve simultaneous noise and input matching. Spiral inductor in input circuit of LNA inserted PGS for betterment of Q-factor. we modeling inductor using EM simulator, so compared with inductor of TSMC 0.18um. We designed and simulation the optimum structure of PGS using Taguchi's method. We confirmed enhancement of noise figure at LNA after substituted for inductor with PGS. Mixer designed using current bleeding techniques for reduced noise. We designed LNA using inductor with PGS and Mixer using current bleeding techniques, so confirmed improvement of noise figure.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권12호
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• pp.649-654
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• 2003

The simplest method for measuring output currents of the three phase inverters is to measure them with three current sensors such as hall sensors. This method requires at least two current sensors, and these types of sensors are somewhat expensive. More economical method is measuring DC link current with a simple shunt resistor, then, reconstructing output current using the DC link current value and the switching status. However, in low speed region, the measurement becomes difficult and even impossible due to the requirement of minimum switching duration for A/D conversion. These problems can be overcome by limitation of switching duration. Limitation of switching, however, causes voltage and current distortion. Owing to compensation, distortion can be effectively suppressed. However these increase acoustic noise due to increment of current ripple. In this paper, a current measurement method is proposed, which can reduce minimum switching duration resulting in reduction of acoustic noise. The validity of proposed method is confirmed through experiment.

• 전자공학회논문지
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• 제54권2호
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• pp.53-57
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• 2017

본 논문에서는 의료 기기용 401MHz - 406MHz MedRadio 대역에서 사용하는 저잡음 증폭기를 제안한다. 제안한 저잡음 증폭기는 전류 재사용 gm-boosting 기술을 이용한 공통 게이트 증폭기 구조를 채택하여 기존의 gm-boosted 공통 게이트 증폭기에 비해 동일한 전력소모에서 더 높은 전압 이득과 더 낮은 잡음 지수 특성을 얻었다. 제안한 전류 재사용 gm-boosted 저잡음 증폭기는 $0.13{\mu}m$ CMOS 공정을 사용하여 설계하였고, 22 dB의 전압 이득, 2.95 dB의 잡음 지수, -17 dBm의 IIP3 특성을 보이며, 공급 전압 0.5 V에서 $170{\mu}W$의 전력을 소비한다.

• 한국초전도ㆍ저온공학회논문지
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• 제15권2호
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• pp.20-23
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• 2013

For sensitive measurements of micro-Tesla nuclear magnetic resonance (${\mu}T$-NMR) signal, a low-noise superconducting quantum interference device (SQUID) system is needed. We have fabricated a liquid He dewar for an SQUID having a large diameter for the pickup coil. The initial test of the SQUID system showed much higher low-frequency magnetic noise caused by the thermal magnetic noise of the aluminum plates used for the vapor-cooled thermal shield material. The frequency dependence of the noise spectrum showed that the noise increases with the decrease of frequency. This behavior could be explained from a two-layer model; one generating the thermal noise and the other one shielding the thermal noise by eddy-current shielding. And the eddy-current shielding effect is strongly dependent on the frequency through the skin-depth. To minimize the loop size for the fluctuating thermal noise current, we changed the thermal shield material into insulated thin Cu mesh. The magnetic noise of the SQUID system became flat down to 0.1 Hz with a white noise of 0.3 $fT/{\surd}Hz$, including the other noise contributions such as SQUID electronics and magnetically shielded room, etc, which is acceptable for low-noise ${\mu}T$-NMR experiments.