共查询到19条相似文献,搜索用时 125 毫秒
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针对信号调制类型识别的问题,提出一种新的基于分形盒维数和归一化峰度的信号调制类型识别算法.该算法具有计算复杂度低、抗噪性能强的优点.仿真实验结果表明该算法在高斯白噪声环境下信噪比大于-5 dB时,实验使用的几种信号的平均分类正确率超过97%,信噪比大于0 dB时,分类正确率均接近100%. 相似文献
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基于同步地球轨道(Geostationary Earth Orbit, GEO)卫星的机会源技术已被证明其在近岸海面高度测量中的应用潜力,但目前研究主要围绕可行性论证展开,极少开展全方位的测量性能评估.为此,从仿真和试验两个角度评估了信号带宽、非相干累加次数、信噪比及波形峰值跟踪算法对GEO卫星机会源海面测高性能的影响.评估结果表明当非相干累加次数和信噪比大于最优非相干累加次数和最优信噪比时,测高性能将不再显著提升.因此,通过选择最优非相干累加次数,以及设计合理的接收天线增益、射频增益及接收机带宽使信噪比大于最优信噪比对GEO卫星机会源海面测高至关重要.通过对比插值和拟合两种波形跟踪算法发现拟合法能提供比插值法更高的测量精度.利用北斗B3I信号和ASTRA 19.2 E卫星信号开展GEO卫星海面测高的试验评估.试验结果表明:在非相干累加次数大于10 000、信噪比大于7 dB时,北斗B3I信号和ASTRA 19.2 E卫星信号可分别提供精度约为0.20 m和0.10 m的海面高度.针对GEO卫星多频或多通道传输特点,提出了基于信号频谱合成提高海面测高精度的方法 .当利用中卫1号卫星10... 相似文献
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经 36 ke V Xe+注入 ,可在 Na Cl晶体表面产生 F、R1 、R2 和 M等色心。在 10 K温度下的吸收光谱中观测到位于 6 32 .1nm波长处的 R2 色心的零声子线 ,并在不同温度下对零声子线的光谱特性和热稳定性进行了研究。利用 NMR方法 ,首次观测到经 Xe+ ,注入 Na Cl晶体中 2 3 Na的化学位移。经 Xe+ 注入的 Na Cl晶体中 2 3 Na相对于未注入 Na Cl晶体中 2 3 Na的化学位移为 17× 10 - 6 ,预示 Xe+注入的 Na Cl晶体中固态 Na Xe分子的形成。 相似文献
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为研究空间相干光通信的信噪比受本振光功率、探测器特性和光波偏振态的影响,对探测器在不同工作状态下以及光波偏振态变化时的信噪比进行了研究,讨论了在不同工作状态下探测器特性参数和本振光功率对信噪比的影响,并通过实验验证了本振光功率和光波偏振态对信噪比的影响。结果证明空间相干光通信中探测器特性参数限制了本振光功率的取值,实际最大信噪比小于理论值,最佳本振光功率大于理论值,且两光束的偏振方向越接近,输出信噪比越大,最佳本振光功率越小。 相似文献
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A novel midinfrared sensor, called the quantum-dot avalanche photodiode (QDAP), is proposed which is expected to have improved signal-to-noise ratio (SNR) in the presence of Johnson noise over its quantum-dot (QD) counterpart. In the QDAP, an intersubband QD detector is coupled with a thin, low-noise GaAs avalanche layer through a tunnel barrier. The avalanche layer provides the necessary photocurrent gain required to overcome Johnson noise and nearly achieve the dark-current-limited SNR of the QD detector. In the proposed three-terminal device, the applied biases of the QD-detector and the avalanche-photodiode sections of the QDAP are controlled separately. This feature permits the control of the QDs responsivity and dark current independently of the operating avalanche gain, thereby allowing the optimization of the avalanche multiplication factor to maximize the photocurrent's SNR. Notably, a heterojunction potential-barrier layer can also be utilized to further improve the SNR. For example, when the standard deviation of the Johnson noise is four times greater than the dark current, calculations show that the SNR enhancement offered by an avalanche multiplication factor of 5 results in relaxing the cooling requirement from 20 to 80 K. 相似文献
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小波变换在白光干涉数据处理中的应用 总被引:5,自引:2,他引:3
采用小波变换方法对分布式寄生偏振耦合测试仪(DPCA)采样数据进行滤波除噪。实验结果表明,通过采用Daubechies小波对采样数据进行5阶分解、除噪并重建信号后,信噪比(SNR)满足测量要求:SNR从65dB左右提高到80dB以上,SNR增益达到15dB以上,提高了光纤陀螺DCPA对保偏光纤绕组中偏振耦合点的检测灵敏度。 相似文献
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Aiming at the problem that the existing method has high computational complexity and high SNR,a novel method of multi-component SFM signals parameter estimation based on EM algorithm was proposed as to spinning tar-get's narrow band micro-motion echoes.The echo model of spinning target and its micro-doppler measurements based on time-frequency analysis were given.The iterative parameter estimation steps based on Gaussian mixture model and EM algorithm to measurements were established.The simulation results demonstrate that when SNR is greater than -3 dB and the SFM components are equal or greater than 2,the method can estimate the target’s micro-motion parameters e.g.projection size accurately in narrow band condition. 相似文献
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A wavelet-based method for action potential detection from extracellular neural signal recording with low signal-to-noise ratio 总被引:8,自引:0,他引:8
We present a method for the detection of action potentials, an essential first step in the analysis of extracellular neural signals. The low signal-to-noise ratio (SNR) and similarity of spectral characteristic between the target signal and background noise are obstacles to solving this problem and, thus, in previous studies on experimental neurophysiology, only action potentials with sufficiently large amplitude have been detected and analyzed. In order to lower the level of SNR required for successful detection, we propose an action potential detector based on a prudent combination of wavelet coefficients of multiple scales and demonstrate its performance for neural signal recording with varying degrees of similarity between signal and noise. The experimental data include recordings from the rat somatosensory cortex, the giant medial nerve of crayfish, and the cutaneous nerve of bullfrog. The proposed method was tested for various SNR values and degrees of spectral similarity. The method was superior to the Teager energy operator and even comparable to or better than the optimal linear detector. A detection ratio higher than 80% at a false alarm ratio lower than 10% was achieved, under an SNR of 2.35 for the rat cortex data where the spectral similarity was very high. 相似文献
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针对underlay认知无线电中时频重叠正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)信号的信噪比(Signal to Noise Ratio,SNR)难以估计的问题,提出了一种基于循环自相关特性的时频重叠OFDM信噪比盲估计方法.该方法提取接收信号的循环自相关函数截面中的离散谱线估计出分量信号的总功率,并结合时延和循环频率均为零时的离散谱线估计出时频重叠OFDM信号的信噪比.仿真结果表明,在无需先验信息的情况下,当SNR大于-7dB时,所提方法估计的均方误差小于0.1,并且对分量信号的功率比和频谱重叠率具有稳健性. 相似文献
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提出了一种以八相移键控(8PSK)为净荷、ASK为标记的新型高谱效率高速正交光标记交换技术,首次实现了100 Gbit/s的高速正交光标记信号的80 km传输.分析了光信噪比(OSNR)、窄带滤波效应、信道中的非线性效应对标记与净荷性能的影响,并采用平衡相关探测和多符号相位估计(MSPE)技术实现了净荷8PSK信号的接收.与传统接收方式相比,8PSK净荷在相同误码率条件下,OSNR容限提升了约3 dB.经过80 km传输,ASK标记在BER=10~(-9),时OSNR为22.8 dB,8PSK相应的OSNR为20.3 dB. 相似文献
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针对基于子空间分解信噪比估计算法中信号子空间维数估计复杂度高、小样本条件下估计偏差大的问题,提出了一种改进的盲信噪比估计算法.该算法首先构造接收信号的自相关矩阵,然后从矩阵奇异值序列的尾部开始,间隔两项依次进行差分得到梯度序列,再以梯度序列相邻两项均值大干特定阈值为条件确定信号子空间的维数,最后求得信噪比.仿真结果表明:信噪比范围为-5~+15 dB时,平坦衰落信道下常用调制信号的信噪比估计标准差小于0.1 dB,与MDL,AIC方法相比,该算法计算量小,且能适应更低的信噪比和更短的数据长度. 相似文献