共查询到20条相似文献,搜索用时 171 毫秒
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针对光纤干涉仪存在的相位衰落问题,讨论了基于正弦波形的频率调制连续波(FMCW)和锯齿波FMCW两种干涉型光纤声传感器的信号检测原理,并给出了数字化信号解调方案。采用7.5 m臂差的光纤声传感器和具备调频功能的半导体激光器,对10 kHz正弦波FMCW和锯齿波FMCW两种调频方式进行了信号解调实验对比。解调结果表明,两种调制解调方案均能稳定检测出加在声传感器上的模拟声信号,消除了光纤干涉仪的相位衰落。但在实际工程应用中,与正弦波FMCW检测方案相比,锯齿波FMCW方案无需检测混频信号的初始相位,检测灵敏度高且稳定,算法实现更为简单,而且使用不同臂差的光纤传感器可实现传感器的频分复用。 相似文献
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远程传输光纤受环境的影响会在水听器系统中引入噪声,利用迈克耳孙光纤干涉仪模拟光纤水听器,搭建了远程光纤水听器系统,采用参考干涉仪法解调对传输光纤引入的噪声进行抑制。实验结果表明,与常用的相位产生载波技术(PGC)解调相比,参考干涉仪法解调在不影响传感水听器对声信号检测能力的情况下,对传输光纤引入的扰动噪声能进行良好的抑制,频率为500 Hz噪声的抑制量可达到约25 d B,同时该方法使传感水听器系统中100 Hz位置的本底噪声也降低了17 d B。 相似文献
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激光器强度噪声对光纤水听器相位载波解调的影响 总被引:1,自引:1,他引:1
相位载波(PGC)调制解调技术作为光纤水听器主要的检测技术之一,已经应用于许多光纤水听器阵列系统之中,该方案对光源提出了窄线宽、可调谐、低噪声等较高的要求。实验中发现,光源弛豫噪声对系统噪声性能产生了较大的影响。在理论分析光源弛豫噪声对相位载波解调影响的基础上,提出了通过调节抽运功率,控制弛豫振荡中心频率为相位载波调制频率的半倍频的奇数倍,来降低系统解调噪声的方法,实验验证了理论结果,解调噪声由最高的—86.7 dB减小到—106 dB。实验进一步采用了光电负反馈方法来抑制弛豫噪声,在弛豫振荡峰处抑制噪声约25 dB,得到了约—100 dB的较为平坦的激光器噪声谱级,使得相位载波解调噪声达到—110 dB,基本满足了光纤水听器系统的要求。 相似文献
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针对现有技术获得的光信号采样点之间的欧式距离较大,导致解调后信号还原度不高,为此提出基于数据挖掘算法的光纤光栅传感器复用解调技术。利用数据挖掘与分割聚类的基本思想,将光纤光栅传感器信号采样点中的噪声信号剥离,并提取信道中调制信号的相位信息;根据提取结果利用内调制与外调制相结合的双重方法获取光信号相位差净值,完成对光纤光栅传感器复用信号的解调,并保留了原始基带信号中的细节信息。实验测试结果表明,提出解调技术的信号还原度优于传统技术,解调后信号的相位变化与初始信号趋于一致,说明该技术具有极高的应用价值。 相似文献
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柯尊灵黄文涛 《光纤与电缆及其应用技术》2022,(4):1-5
干涉型光纤水听器将目标声压信号调制在激光相位上,需要进行相位解调才能恢复出目标声压信号。提出一种干涉型光纤水听器移频正交解调方法,采用移频与延时装置产生一个具有固定光频差的激光脉冲对,配合光纤水听器单元的两条干涉臂之间的特定程差,形成正交信号,同时利用干涉脉冲和参考脉冲的幅值比例关系,主要依靠简单的数学乘加运算即可实现相位解调。实测结果表明,本方法解调结果准确,抗光功率波动干扰能力强,本底噪声性能优异,可以满足光纤水听器的实际应用需求。 相似文献
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针对淹没在1/f噪声中的有用信号恢复问题,本文提出了一套基于双正交小波变换与Wiener滤波的多尺度滤波算法,并设计出多尺度Wiener滤波器.首先,利用双正交小波变换将带有1/f噪声的信号分解成多尺度的子带信号,通过小波变换对1/f噪声的白化作用,消除了1/f噪声的非平稳性、自相似性和长程相关性.其次,在小波域内,利用Wiener滤波,实现了噪声和有用信号的分离,估计出了各子带中的有用信号.最后,利用双正交小波的精确重构性,较好地恢复出淹没在1/f噪声中的有用信号.仿真实验表明,该滤波器能有效的抑制分形噪声,显著地提高信噪比. 相似文献
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A transform domain SVD filter for suppression of muscle noise artefacts in exercise ECG's 总被引:1,自引:0,他引:1
The proposed filter assumes the noisy electrocardiography (ECG) to be modeled as a signal of deterministic nature, corrupted by additive muscle noise artefact. The muscle noise component is treated to be stationary with known second-order characteristics. Since noise-free ECG is shown to possess a narrow-band structure in discrete cosine transform (DCT) domain and the second-order statistical properties of the additive noise component is preserved due to the orthogonality property of DCT, noise abatement is easily accomplished via subspace decomposition in the transform domain. The subspace decomposition is performed using singular value decomposition (SVD). The order of the transform domain SVD filter required to achieve the desired degree of noise abatement is compared to that of a suboptimal Wiener filter using DCT. Since the Wiener filter assumes both the signal and noise structures to be statistical, with a priori known second-order characteristics, it yields a biased estimate of the ECG beat as compared to the SVD filter for a given value of mean-square error (mse). The filter order required for performing the subspace smoothing is shown to exceed a certain minimal value for which the mse profile of the SVD filter follows the minimum-mean-quare error (mmse) performance warranted by the suboptimal Wiener filter. The effective filter order required for reproducing clinically significant features in the noisy ECG is then set by an upper bound derived by means of a finite precision linear perturbation model. A significant advantage resulting from the application of the proposed SVD filter lies in its ability to perform noise suppression independently on a single lead ECG record with only a limited number of data samples. 相似文献
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本文提出了一种基于OFDM(Orthogonal Frequency Division Multiplexing)系统的两次一维(2×1-D)维纳滤波信道估计的噪声方差优化方法.对于2×1-D维纳滤波信道估计,维纳滤波将先后应用于频域维和时域维,而两次滤波时的噪声方差实际是不相同的,但现有的2×1-D维纳滤波信道估计方法没有考虑噪声的变化.本文首先分析出了第一次滤波后残余的噪声方差,并将其优化的结果应用于第二次滤波中,然后根据不同的优化准则对信道估计性能进行了评估.仿真结果表明,同未对噪声方差优化的信道估计方法相比,本方法具有更优的性能,且非常接近两维维纳(2-D)滤波方法. 相似文献
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基于沃尔泰拉理论的集总光纤非线性噪声补偿 总被引:3,自引:1,他引:3
通过沃尔泰拉(Volterra)级数理论求得了非线性薛定谔方程(NLSE)的半解析解,在考虑光纤损耗、色散及非线性效应的情况下,推出了长距离在线级联掺铒光纤放大器(EDFA)光纤通信系统中信号和自发辐射噪声(ASE)之间耦合串扰的半解析表达式,得到了多跨距传输接收端输出信号和发射端输入信号之间的关系式.根据维纳(Wiener)滤波理论的时域滤波原理,在多跨距传输系统接收端设计了对非线性乘性噪声有滤波作用的维纳滤波器,并对预集总色散补偿、后集总色散补偿、分布链路色散补偿系统及一对三"跨距成比例平移对称的色散非线性同步补偿系统进行了仿真模拟研究.结果表明了提出的设计思路及方法的可行性,为进一步提高传输距离增大入纤功率提供了新的思路. 相似文献
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The authors address the problem of enhancing hybrid magnetic resonance (MR) images degraded by T2 effects and additive measurement noise. To reduce imaging time, MR signals are acquired using hybrid imaging (HI) sequences such as rapid acquisition relaxation-enhanced (RARE) and fast spin-echo (FSE). With these techniques, T2 effects act as a distortion filter. This T2 filter affects the signal and results in image spatial resolution and/or contrast loss. Furthermore, the amplitude and phase discontinuities in the T2 filter frequency response function may generate serious ringing artifacts. These distortions will damage image quality and affect object detectability. The authors use the Wiener filter and linear prediction (LP) technique to process HI MR signals in the spatial frequency domain (K-space) and the hybrid domain, respectively. Based on the average amplitude symmetry constraint of the spin echo signal, the amplitude frequency response function of the T2 distortion filter can be estimated and used in the Wiener filter for a global T2 amplitude restoration. Then, the linear prediction technique is utilized to obtain the local signal amplitude and phase estimates around the discontinuities of the frequency response function of the T2 filter. These estimates are used to make local amplitude and phase corrections. The effectiveness of this combined technique in correcting T2 distortion and reducing the measurement noise is analyzed and demonstrated using experiments on both phantoms and human studies. 相似文献
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Empirical mode decomposition (EMD) is a powerful algorithm that decomposes signals as a set of intrinsic mode function (IMF)
based on the signal complexity. In this study, partial reconstruction of IMF acting as a filter was used for noise reduction
in ECG. An improved algorithm, ensemble EMD (EEMD), was used for the first time to improve the noise-filtering performance,
based on the mode-mixing reduction between near IMF scales. Both standard ECG templates derived from simulator and Arrhythmia
ECG database were used as ECG signal, while Gaussian white noise was used as noise source. Mean square error (MSE) between
the reconstructed ECG and original ECG was used as the filter performance indicator. FIR Wiener filter was also used to compare
the filtering performance with EEMD. Experimental result showed that EEMD had better noise-filtering performance than EMD
and FIR Wiener filter. The average MSE ratios of EEMD to EMD and FIR Wiener filter were 0.71 and 0.61, respectively. Thus,
this study investigated an ECG noise-filtering procedure based on EEMD. Also, the optimal added noise power and trial number
for EEMD was also examined. 相似文献
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Multiscale Wiener filter for the restoration of fractal signals:wavelet filter bank approach 总被引:4,自引:0,他引:4
Bor-Sen Chen Chin-Wei Lin 《Signal Processing, IEEE Transactions on》1994,42(11):2972-2982
A filter bank design based on orthonormal wavelets and equipped with a multiscale Wiener filter is proposed in this paper for signal restoration of 1/f family of fractal signals which are distorted by the transmission channel and corrupted by external noise. First, the fractal signal transmission process is transformed via the analysis filter bank into multiscale convolution subsystems in time-scale domain based on orthonormal wavelets. Some nonstationary properties, e.g., self-similarity, long-term dependency of fractal signals are attenuated in each subband by wavelet multiresolution decomposition so that the Wiener filter bank can be applied to estimate the multiscale input signals. Then the estimated multiscale input signals are synthesized to obtain the estimated input signal. Some simulation examples are given for testing the performance of the proposed algorithm. With this multiscale analysis/synthesis design via the technique of the wavelet filter bank, the multiscale Wiener filter can be applied to treat the signal restoration problem for nonstationary 1/f fractal signals 相似文献