• 한국전자파학회논문지
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• 제7권3호
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• pp.230-238
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• 1996

본 논문에서는 임펄스 잡음이 존재하는 레일리 페이딩 환경에서 다이버시티 기법에 의한 BFSK신호의 성능 개선치를 구하였으며 이를 가우스잡음의 경우와 비교하였다. Rayleigh 페이딩 환경하에서는 CNR 값이 클수록 임펄스 잡음의 영향에 관계없이 일정한 선호 성능에 수렴한 다는 것을 알았다. 또한 다이버시티 기법은 가우스 잡음뿐만 아니라 임펄스 잡음과 페이딩이 혼재하는 통신 환경 에서도 선호의 성능을 개선시킬 수 있음을 알았다. 또한 레일리 페이딩과 임펄스 잡음이 혼재하는 통신로 환경에 서 다이버시티 기법과 부호화 기법을 같이 사용하면 부호화 기법만을 사용한 경우에 비해 신호의 오율성능이 약 11[dB] 정도 개선 됨을 알았다.

• 한국산업정보학회논문지
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• 제20권1호
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• pp.49-55
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• 2015

This paper proposes a 2.4 GHz RF oscillator with a very low close-in phase noise performance. This is composed of a low frequency crystal oscillator and three frequency multipliers such as two doubler (X2) and one tripler (X3). The proposed oscillator is implemented as a hybrid type circuit design using a discrete silicon bipolar transistor. The measurement results of the proposed oscillator structure show -115 dBc/Hz close-in phase noise at 10 kHz offset frequency, while only dissipating 5 mW from a 1-V supply. Its close-in phase noise level is very close to that of a low frequency crystal oscillator with little degradation of noise performance. The proposed structure which is consisted of a low frequency crystal oscillator and a frequency multiplier provides new method to implement a low power low close-in phase noise RF local oscillator.

• 대한음성학회지:말소리
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• 제64호
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• pp.105-119
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• 2007

Noise reduction technologies are indispensable to achieve acceptable speech quality in VoIP systems. This paper proposes a Wiener filter optimized to the estimated SNR of noisy speech for the noise reduction in VoIP environments. The proposed noise canceller is applied as a pre-processor before speech encoding. The performance of the proposed method is evaluated by the PESQ in various noisy conditions. In this paper, the proposed algorithm is applied to G.711, G.723.1, and G.729A which are all VoIP speech codecs. The PESQ results show that the performance of our proposed noise reduction scheme outperforms those of the noise suppression in the IS-127 EVRC and the ETSI standard for the advanced distributed speech recognition front-end.

• 전기학회논문지
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• 제61권10호
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• pp.1489-1495
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• 2012

In this study, the active noise control experiment has been performed using induction motor noises. While the noises were measured, a induction motor was operated in different speed. For the simulation of ANC(Active Noise Control), test-bed is composed a multi-channel ANC system was constructed. In order to compare the control performance, we performed noise reduction simulations of ANC by Co-FXLMS algorithm and FXLMS algorithm. Through the simulation results, we confirmed that convergence performance and noise decrease effect of the proposed Co-FXLMS algorithm have been improved from existing FXLMS algorithm.

• 한국군사과학기술학회지
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• 제16권3호
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• pp.373-381
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• 2013

In this paper, the effects of phase noise on the radar system were analyzed in terms of 3 point of view. The impact(s) on the compressed pulse waveform, the FMICW(Frequency Modulated Interrupted Continuous Wave) radar performance and the receiver sensitivity were investigated. From the investigation, it was indicated that the phase noise over 10 kHz offset frequency makes the side lobe level of compressed pulse worse. Also it was founded that the FMICW radar performance, especially at the noise level of range profile, is related to the phase noise. Finally, the investigation showed that the phase noise at local oscillator affects the receiver sensitivity.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.1949-1960
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• 2003

This paper presents vibration and noise control of flexible structures using squeeze mode electro-rheological mounts. After verifying that the damping force of the ER mount can be controlled by the intensity of the electric fild, two different types of ER squeeze mounts have been devised. Firstly, a small size ER mount to support 3 kg is manufactured and applied to the frame structure to control the vibration. An optimal controller which consists of the velocity and the transmitted force feedback signals is designed and implemented to attenuate both the vibration and the transmitted forces. Secondly, a large size of ER mount to support 200 kg is devised and applied to the shell structure to reduce the radiated noise. Dynamic modeling and controller design are undertaken in order to evaluate noise control performance as well as isolation performance of the transmitted force. The radiated noise from the cylindrical shell is calculated by SYSNOISE using forces which are transmitted to the cylindrical shell through two-stage mounting system.

• 한국정밀공학회지
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• 제20권9호
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• pp.151-158
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• 2003

The impulse noise of bullet after shooting in small arms has an effect on the hearing ability of human. Although a silencer has been developed for noise reduction in small arms, there is only a few researches about relationships between the sound pressure level and the auditory sense of human. In this study, the quantitative sound pressure levels are revealed by experimental measurements of impulse noise with each silencer type. And the performance evaluation for noise suppression of a silencer in small arms is carried out to reduce a serious loss of the hearing ability of the small arms user. It is concluded that the evaluated results can be utilized for checking sound pressure and data accumulation for new small arms design with silencer.

• 소음진동
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• 제6권6호
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• pp.851-856
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• 1996

The active noise cancellation system showing the effective convergence and stability has been studied by simplifying the controller structures using the weighting factors of control error path to the multi-channel filtered-x LMS algorithm which needs a lot of calculations and the performance has been verified experimentally. Besides, to implement the system performance in a vehicle cabin, experimental work for selecting the suitable numbers and positions of the microphones and speakers was accomplished. Effectively combining a TMS 320C 31 main processor conducting real number calculations and having various functions with other components, the purpose-built system board for active noise cancellation has been designed and with this board, car active noise cancellation system showing maximum stable 10dB noise reduction has been obtained at the car idling conditions above 3000rpm range.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.350-354
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• 2008

Low frequency exhaust noise of marine diesel engine is one of the most important noise sources in vessels. However, conventional absorptive silencers are limited because the absorptive material is not effective in low frequency range. In the paper, exhaust noise control of marine diesel engine has been studied by using the resonator type silencer, which was composed of concentric hole-cavity resonators. The acoustic performance of the resonator type silencer was verified by the insertion loss measurement considering flow effect. Consequently, its high performance, about $5{\sim}8dB$ noise reduction, in the low frequency range was confirmed by insertion loss measurements conducted in the ship.

• 한국음향학회지
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• 제19권8호
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• pp.26-34
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• 2000

This paper presents a new adaptive impulse noise cancelling technique based on the adaptive nonlinear suppressing function. The proposed "adaptive threshold algorithm (ATA)" is controlled by the normalized power prior input data term, and this adaptive threshold makes the cancelling system highly robust against additive impulse noise. For the performance evaluation, we have tested the proposed algorithm with the observed signals simulated in various impulsive noise environments and real EMG signals. As a result the proposed algorithm shows superior performance of 51.7% to the available techniques in the points of SNR and MSE.