共查询到19条相似文献,搜索用时 171 毫秒
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离散时间系统中的噪声辅助信号传输 总被引:5,自引:1,他引:4
基于一种平均信噪比讨论了离散时间系统中的三种典型噪声辅助信号传输的问题.仿真得到:当输入周期信号在阈下时,噪声能辅助信号的传输,随机谐振现象存在.存在一个噪声强度范围,其间系统的输出平均信噪比大于其输入平均信噪比,即输出输入平均信噪比增益大于1.随机谐振的功效随着系统阈值的增加,或噪声概率密度函数的拖尾变厚、零均值周边脉冲变窄而降低.这些结果同样说明了离散时间系统中随机谐振的复杂性,它的存在和功效也依赖于系统性能的测度和噪声类型.这些结果拓广了随机谐振在数字信号处理中的应用. 相似文献
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采用低频超声胸腔成像技术对实际的人体胸腔进行信号采集时,超声换能器接收到的胸腔信号中会含有大量的噪声干扰,较大地影响了成像效果。因此文章通过COMSOL平台建立二维胸腔模型,在接收到的胸腔信号中添加信噪比为2dB高斯白噪声作为模拟噪声。通过小波阈值降噪技术对含噪的胸腔信号进行处理,发现db7小波基在分解层数为1层,阈值准则为minimaxi,软阈值处理函数时可以有效降噪,提高数据的信噪比。 相似文献
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一、最佳判决电平的确定判决即信号的检测。在光纤数字通信系统中,由于光纤信道以及接收机频率特性和噪声的影响,会使接收端信号波形畸变。这种畸变一般来说是复杂的、随机的。判决的目的就是要克服这种畸变,以便从接收信号中提取所发送的序列。当然,判决电路完全克服畸变是不可能的,这里就要根据最佳检测理论,确定在一定的假设条件下满足某种准则的最佳判决。对于大多数通信系统,感兴趣的最佳准则是最小错误概率准则。下面具体讨论一下在最小错误概率准则下判决电路的错误概率(也称误码率)。设通信系统是二进制的,即只有两个信 相似文献
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周期脉冲信号在阈值系统中随机共振特性研究 总被引:1,自引:0,他引:1
研究含有高斯白噪声的周期脉冲信号,通过阈值系统后的随机共振特性。在一定条件下因系统、信号、噪声的协同作用而产生随机共振现象,在某一最优噪声强度下获得最大的信号幅度放大及信噪比增益。讨论了仿真实验中一些有益的发现和可能的应用。 相似文献
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针对已有的随机接入前导算法存在难以在实际基站中实现以及算法运算量大的缺点,文章提出了5G随机接入前导检测算法。首先将接收到的信号经过发送端的逆过程处理得到频域前导,然后生成频域ZC序列并进行分组,将各个组内频域ZC序列相加并与频域前导相关,最后通过设置阈值来检测前导序列,利用多天线分集梳理修改相对阈值的累积分布函数,根据相对检测阈值确定绝对检测阀值,即相对检测阈值与时变噪声电平的乘积。仿真结果表明,与频域固定阈值前导检测算法相比,在加性高斯白噪声信道中,所提算法的正确检测概率性能提升了1 dB;在节拍延迟线(TDLC300-100)信道中,所提算法的正确检测概率性能提升了2 dB。 相似文献
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目标识别是雷达探测领域研究的难点问题,本文利用无载频脉冲探地雷达系统对有耗媒质中细长导线状和环状金属目标的瞬态散射特性进行了实验测量,并利用极点展开理论对谐振现象的产生给予了分析和讨论。在瞬态脉冲激励下,有耗媒质中的目标能够产生外部振荡现象,目标谐振时雷达接收信号的幅值比非谐振时大得多。谐振信号的产生与目标形状和特性、媒质参数、激励脉冲的宽度和天线极化特性等因素有关。 相似文献
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在Neyman-Pearson准则下,对于贝叶斯检测前跟踪算法,为了能够按照系统要求的虚警概率实时地设置检测阈值,该文在观测噪声为复高斯白噪声的情况下推导得到了检测阈值的近似闭式解。对于贝叶斯检测前跟踪算法,该文从似然比检测形式入手,推导了检测统计量的表达式,得到了系统虚警概率同检测阈值之间的关系,并在观测噪声为复高斯白噪声的情况下给出了检测阈值的近似闭式解。计算机仿真实验表明,利用该检测阈值的近似闭式解,可以按照系统要求的虚警概率实时地计算检测阈值,从而使得实际系统的虚警概率满足要求。 相似文献
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In error controlled packet reception, a packet is received only if its error probability can be kept below a predetermined level. Error probability control is achieved by posing a minimum signal to noise ratio (SNR) threshold with corresponding packet internal coding scheme, which upper-bounds the packet data rate. We first consider packet transmission over a single-user wireless fading channel with additive Gaussian noise. We derive the optimal SNR threshold that maximizes the communication throughput. We show under a set of generous conditions that the optimal SNR threshold in the low-SNR regime is proportional to the transmit power; the ratio depends neither on the packet internal coding scheme nor on the pre-determined error probability level. The result is then extended to packet multicasting where common information is transmitted to a group of receivers over fading channels. 相似文献
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The delay-lock discriminator is a nonlinear feedback system which employs a form of cross correlation to estimate the relative delay between a reference signal and a delayed version of that signal which is perturbed with additive noise. Previous treatments of delaylock tracking have assumed that the binary maximal-length code sequences used as the signal are detected in a coherent manner. The present paper is concerned with delay-lock discriminator tracking behavior when noncoherent detection of the received signal is required and when two-bit quantization is employed to reduce the cost of implementation of the cross-correlation network. It is found that the error signal generated by the cross-correlation network is characterized by "clustering" in the absence of noise, however, this mode of error signal behavior gradually vanishes as the noise level is increased and is replaced by an error signal generation characteristic that more closely resembles the behavior that obtains without quantization. The selection of an appropriate threshold value to achieve minimum steady-state errors for the delay-lock discriminator is reduced to the problem of determining the probability density function of the error signal under the condition of exact alignment. 相似文献
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WANG You-guo WU Le-nan ZHANG Dan.School of Mathematics Physics Nanjing University of Posts Telecommunications Nanjing P. R. China .Department of Radio Engineering Southeast University Nanjing P. R. China .School of Telecommuncation Information Engineering Najing University of Posts Telecommunications Nanjing P.R. China 《中国邮电高校学报(英文版)》2006,13(1):79-83
1IntroductionSometi mes,noise can i mprove signal transmission orsignal processing in a nonlinear system.This phe-nomenonis the so-called Stochastic Resonance(SR)[1].Most studies of SRinvolve asubthresholdsignal througha single nonlinear systemand the non… 相似文献
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In this paper, end‐to‐end performance of transmit antenna selection (TAS) and generalized selection combining (GSC) is studied in a dual‐hop amplify‐and‐forward relay network over flat Rayleigh fading channels. In the system, source and destination equipped with multiple antennas, communicate by the help of single relay equipped with single antenna. Source‐destination link is not available. TAS is used for transmission at the source, and GSC is used for reception at the destination. By considering the relay location and the presence of error in feedback channel from the relay to the source, we derive closed‐form outage probability, moment generating function and moments of end‐to‐end signal‐to‐noise ratio, and closed‐form symbol error probability (SEP) expressions for channel state information (CSI)‐based and fixed relay gains. The diversity order and array gain of the network are obtained for both CSI‐based and fixed relay gains by deriving asymptotical outage probability and SEP expressions. The analytical results are validated by the Monte Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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A novel constant false alarm rate (CFAR) intrusion detection method based on stochastic resonance (SR) is proposed in this
paper. Using the SR technique improves the spectral power (SP) and the signal-to-noise ratio (SNR) of the network intrusion
signal, hence enhancing the detectability of network attacks. The threshold and the detection probability of the proposed
SR-CFAR method are derived theoretically. Computer simulations based on standard Defense Advanced Research Projects Agency
(DARPA) network intrusion data show that this CFAR method outperforms the linear anomaly intrusion detection methods for various
types of intrusions. 相似文献
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利用小波包理论对车载移动电话的接收信号进行小波包变换,通过设定一合适的阈值对变换后的信号进行量化处理.提取出主要由发动机产生的噪声信号,然后用实际检测信号减去小波包变换信号,得出汽车司机的语音信号.从而达到消除噪声的目的。利用MATLAB的小波工具箱对所提出的方法进行验证,结果表明提取后的信号与驾驶员的声音信号十分相似,误差较小,对发动机噪声有明显的抑制作用。 相似文献
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针对同步挤压小波变换(SST)消噪过程中仅使用单一阈值的不足,对SST消噪时的幅度阈值进行了改进,提出了一种基于SST分层阈值的混沌信号消噪方法.首先,根据信号和噪声经SST分解后系数的分布模型,推导SST混沌去噪时幅度阈值权系数的均方误差计算公式;进而,根据均方误差最小准则,计算幅度阈值权系数的最优取值;最后,根据最优阈值权系数和噪声标准差,确定SST混沌去噪时的分层阈值.利用模拟混沌信号和实测月太阳黑子信号对所提方法进行了实验分析,实验结果表明,本文方法可较好地滤除混沌信号中的噪声,同时原始信号的内在混沌特性也能得到较大程度的恢复.与小波阈值法和集合经验模态分解(EEMD)消噪法相比,可获得更好的消噪效果. 相似文献