• Title, Summary, Keyword: 신호대잡음비

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PN Code Acquisition at Low Signal-to-Noise Ratio Based on Seed Accumulating Sequential Estimation (시드 누적 순차적 추정 기법을 이용한 낮은 신호대잡음비 환경에서의 의사 잡음 부호 획득)

  • 윤석호;김선용
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.9A
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    • pp.678-683
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    • 2003
  • The pseudo-noise (PN) code acquisition based on the sequential estimation (SE) proposed by Ward performs well only at relatively high chip signal-to-noise ratios (SNRs). In this paper, a seed accumulating sequential estimation (SASE) method and a PN code acquisition system based on it are proposed, which perform well at low chip SNR (of practical interest) also. Then, the mean acquisition time performance of the proposed system is investigated. Numerical results show that the system based on the SASE performs dramatically better than that based on the SE at low chip SNR, and the improvement becomes larger as the period of PN code increases.

Preprocessing Technique for Improvement of Speech Recognition in a Car (차량에서의 음성인식율 향상을 위한 전처리 기법)

  • Kim, Hyun-Tae;Park, Jang-Sik
    • The Journal of the Korea Contents Association
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    • v.9 no.1
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    • pp.139-146
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    • 2009
  • This paper addresses a modified spectral subtraction schemes which is suitable to speech recognition under low signal-to-noise ratio (SNR) noisy environment such as the automatic speech recognition (ASR) system in car. The conventional spectral subtraction schemes rely on the SNR such that attenuation is imposed on that part of the spectrum that appears to have low SNR, and accentuation is made on that part of high SNR. However, such postulation is adequate for high SNR environment, it is grossly inadequate for low SNR scenarios such as that of car environment. Proposed methods focused specifically to low SNR noisy environment by using weighting function for enhancing speech dominant region in speech spectrum. Experimental results by using voice commands for car show the superior performance of the proposed method over conventional methods.

Noise Performance Design of CMOS Preamplifier for the Active Semiconductor Neural Probe (신경신호기록용 능동형 반도체미세전극을 위한 CMOS 전치증폭기의 잡음특성 설계방법)

  • 김경환;김성준
    • Journal of Biomedical Engineering Research
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    • v.21 no.5
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    • pp.477-485
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    • 2000
  • 본 논문에서는 신경신호기록을 위한 반도체 미세전극용 전치증폭기의 잡음특성을 설계하기 위한 체계적인 방법을 제시한다. 세포외기록(extracellular recording)에 의하여 측정된 신경신호와 전형적인 CMOS소자의 저주파 잡음특성을 함계 고려하여 전체 신호대잡음비를 계산하였다. 2단 CMOS 차동증폭기에 대한 해석과 함께 신호대잡음비에 중요한 영향을 끼치는 요소들에 대하여 설명하였다. 출력잡음전력에 대한 해석적인식을 유도하였으며 이로부터 회로설계자가 조절할 수 있는 주파수응답과 소자 파라미터들을 결정하였다. 입력소자의 크기와 트랜스컨덕턴스의 비가 최적영역으로부터 약간 벗어날 경우에 신호대잡음비가 크게 저하됨을 보였다. 이와 함께 만족스런 잡음특성을 위한 증폭이의 설계 변수 값들도 제시하였다.

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Performance Analysis of DS/CDMA System in Multipath Rayleigh fading and Impulsive Noise Environments (다중경로 레일리 패이딩과 임펄스 잡음 환경에서 DS/CDMA 시스템의 성능 분석)

  • 강희곡;조성준;조성언
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • pp.292-296
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    • 2000
  • 본 논문에서는 임펄스 잡음과 다중경로 레일리 페이딩이 함께 존재하는 최악의 채널 환경에서 비동기 DS/CDMA BPSK 시스템의 오율식을 유도하고 수치계산 하여 BER 성능을 분석하였다. 그 결과, 비교적 낮은 신호 대 잡음 전력비 영역에서 시스템의 BER 성능은 임펄스 잡음의 영향으로 크게 열화되지만 페이딩의 영향은 거의 없다. 그러나, 임펄스 잡음의 영향이 작아지는 높은 신호 대 잡음 전력비에서는 페이딩에 의해서 BER 성능이 결정된다. 다중사용자의 간섭도 낮은 신호 대 잡음 전력비 영역에서는 BER 성능에 거의 영향을 미치지 못하지만 높은 신호 대 잡음 전력비 영역에서는 BER 성능을 좌우한다 그러나, 실제 이동통신 시스템에서는 비교적 낮은 신호 전력을 사용하므로, 임펄스 환경에서 페이딩을 경감하기 위한 방법이나, 다중사용자 간섭을 줄이기 위한 기법을 적용하더라도 성능 개선이 거의 되지 않는다.

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Study on Low Temperature Radiofrequencey Coils for the Signal-to-Noise Ratio Improvement of Nuclear Magnetic Resonance (핵자기공명 신호 향상을 위한 저온 고주파코일 연구)

  • Kim, Song-Hee;Lee, Dong-Hoon
    • The Journal of Natural Sciences
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    • v.13 no.1
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    • pp.15-23
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    • 2003
  • 본 연구에서는 코일의 온도를 액체질소 온도 정도의 저온으로 냉각시켜 핵자기공명 신호 및 영상의 신호대잡음비를 향상시키는데 그 목적을 두었다. 핵자기공명 신호의 신호대잡음비에 대한 이론적인 분석을 토대로 다양한 형태의 고주파코일을 제작했고, 저온의 표면고주파코일로 획득된 신호를 상온의 일반 구리코일로 획득된 신호와 비교하였다. 본 연구에서 제작된 저온코일의 경우, 상온코일에 비해서 신호대잡음비의 향상을 얻을 수 있었다. 이러한 신호대잡음비의 향상을 통하여 핵자기공명영상 시간을 단축할 수 있으며, 이를 통한 진단의 신뢰도 향상에 기여할 수 있을 것으로 사료된다.

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Performance Analysis of the Adaptive Coding System Based on Received SNR over a Rayleigh Fading Channel (레일레이 페이딩 채널에서 수신신호의 신호대잡음비에 근거한 적응부호화 시스템의 성능 분석)

  • 허성호;이재홍
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.7B
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    • pp.1270-1281
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    • 2000
  • 본 논문에서는 수신신호의신호대잡음비를 이용하여 작동되는 적응부호화 시스템을 레일레이 페이딩 채널 환경에서 분석한다. 분석에서는 레일레이 페이딩 채널을 수신신호의 신호대잡음비를 K개의 구간으로 나누어서 유한 상태 마르코프 채널로 모델링한다. 채널 상태를 예측하는 과정에서 발생하는 오류확률을 고려하여 적응부호화 시스템의 평균 BER과 throughput이 계산된다. 본 논문에서 제안한 분석 방법을 이용하여 천공 길쌈부호를 이용한는 적응부호화 시스템의 성능을 분석한 결과가 예제로 보여진다.

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Correlation Analysis of Signal to Noise Ratio (SNR) and Suspended Sediment Concentration (SSC) in Laboratory Conditions (실험수로에서 신호대잡음비와 부유사농도의 상관관계 분석)

  • Seo, Kanghyeon;Kim, Dongsu;Son, Geunsoo
    • Journal of The Korean Society of Civil Engineers
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    • v.37 no.5
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    • pp.775-786
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    • 2017
  • Monitoring sediment flux is crucial especially for maintaining river systems to understand morphological behaviors. Recently, hydroacoustic backscatter (or SNR) as a surrogate to empirically estimate suspended sediment concentration has been increasingly highlighted for more efficient acquisition of sediment dataset, which is difficult throughout direct sediment sampling. However, relevant contemporary researches have focused on wide range solution applicable for large natural rivers where H-ADCPs with relatively low acoustic frequency have been widely utilized to seamlessly measure streamflow discharge. In this regard, this study aimed at investigating hydroacoustical characteristics based on a very recently released H-ADCP (SonTek SL-3000) with high acoustic frequency of 3 MHz in order to capitalize its capacity to be applied for suspended sediment monitoring in laboratory conditions. SL-3000 was tested in a laboratory flume to collect SNR in conjunction with LISST-100X for actual sediment concentration and particle distribution in both sand and silt sediment injection in various amount. Conventional algorithms to correct signal attenuations for water and sediment were carefully tested to validate whether they can be applied for SL-3000. As result of analyzing the SNR-SSC correlation trand, through further study in the future, it is confirmed that SSC can be observed indirectly by using the SNR.

Improvement of Signal-to-Noise Ratio for Speech under Noisy Environment (잡음환경 하에서의 음성의 SNR 개선)

  • Choi, Jae-Seung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.7
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    • pp.1571-1576
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    • 2013
  • This paper proposes an improvement algorithm of signal-to-noise ratios (SNRs) for speech signals under noisy environments. The proposed algorithm first estimates the SNRs in a low SNR, mid SNR and high SNR areas, in order to improve the SNRs in the speech signal from background noise, such as white noise and car noise. Thereafter, this algorithm subtracts the noise signal from the noisy speech signal at each bands using a spectrum sharpening method. In the experiment, good signal-to-noise ratios (SNR) are obtained for white noise and car noise compared with a conventional spectral subtraction method. From the experiment results, the maximal improvement in the output SNR results was approximately 4.2 dB and 3.7 dB better for white noise and car noise compared with the results of the spectral subtraction method, in the background noisy environment, respectively.

The Effect of Advanced Modeling Iterative Reconstruction(ADMIRE) on the Quality of CT Images : Non-contrast CT in Chest (고급 모델링 반복 재구성법(ADMIRE)이 CT 영상의 화질에 미 치는 영향: 흉부 비조영 CT에서)

  • Lee, SangHeon;Lee, HyoYeong
    • Journal of the Korean Society of Radiology
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    • v.13 no.2
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    • pp.159-168
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    • 2019
  • We examined the effect of Siemens ADMIRE (Advanced Modeled Iterative Reconstruction) on image quality by measuring changes in HU, noise, and SNR of background air, fat, muscle, and background signals on a chest CT scan. Experimental results show that as the ADMIRE Strength increases, the noise decreases and the signal increases, consequently the signal-to-noise ratio increases. ADMIRE can reduce noise by 28 ~ 61% compared to FBP, which is a conventional image reconstruction algorithm, and improves SNR by 16 ~ 100%.

The Effect of Coating Material of Copper-wire RF Coil on the Signal-to-Noise Ratio in MR Images (RF코일로 사용된 구리선 코팅재질이 자기공명영상에서의 신호대잡음비에 미치는 영향)

  • Lee, Hyeon-Seung;Moon, Hye-Young;Chang, Yong-Min;Hong, Kwan-Soo
    • Investigative Magnetic Resonance Imaging
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    • v.13 no.2
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    • pp.171-176
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    • 2009
  • Purpose : To investigate the effect of coating material in RF coil, which is one of main parts in MRI machine, on the Q-factor and SNR(signal-to-noise ratio) in MR images. Materials and Methods : RF coils with inner diameter of 1.7 mm were made by using copper wires coated with polyester, polyurethane, polyimide, polyamideimide, and polyester-imide, and by using copper wires in which coating materials had been removed. Q-factors of the RF coils were measured by network analyzer, and SNR values in the spin-echo MR images obtained by 600 MHz (14.1 T, Bruker DMX600) micro-imaging system for the coated and uncoated cases. Results : The measured SNRs were almost same for the RF coils with coat-removed copper wires, however SNRs and Q-factors were different for the coated cases depending on the coating material. They were maximized in the polyurethane-coated case in which the SNR was > 30% greater than polyester-coated case. Conclusion : We made solenoid-type RF coils which were easily used for MR micro-imaging in Bruker MRI probe. There was a significant coating-material dependence in the measured Q values and SNRs for the home-made RF coils. The study demonstrated that the choice of coating material of RF coil may be a critical factor in the MRI sensitivity based on SNR value.

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