基于非负约束矩阵分解的语音增强算法研究

从噪声背景中提取尽可能纯净的语音信号，增强有用信号，抑制、降低噪声干扰的技术称为语音增强技术。语音增强有着广泛的应用，因此寻求一种有效的算法对带噪语音信号进行处理得到较纯净的原始语音信号的研究有着很大的意义。多年来很多经典的语音增强算法被提出，如谱减算法，子空间算法等。文章提出了一种新颖的语音增强方法，即基于非负低秩稀疏分解的原理在强噪声环境下实现语音增强。把语音信号和噪声信号看做是一个非负低秩稀疏分解问题并且不断的优化算法分离出语音信号和噪声信号的幅度谱。实验结果表明在强噪声环境下这种方法对比一些传统的语音增强方法效果更好，具有更少的噪声残余与较低的语音失真等优点     

双频谱分析激光多普勒测振系统

研究了一种激光多普勒测振新方法，它甚至在相当大的高斯噪声干扰下也能照常使用。这种方法通过双频谱分析可以将振动的幅度和位相从检测信号和参考信号中间分离出来，因此要用到检测信号的重要的双频谱特性，这个特性反映出频率受振动调制的情况。双频谱分析的应用排除了高斯噪声的干扰，实现了在噪声环境中仍能正常工作的测量系统。实验结果清楚地表明这种方法是有效的。     

高阶统计量在检测中的应用

本文提出了一种利用高阶统计量对加性噪声中的确定性信号及非高斯随机信号进行检测的方法。这种检测方法对加性噪声是否有色或是否为高斯分布并不敏感，而只要求噪声具有对称的概率密度函数，在信号波形未知而造成匹配滤波器性能恶化时，利用这种方法对确定性信号进行检测的性能与已知彼形时匹配滤波器的检测性能相近。在色噪声话密度未知且噪声港与信号谱重叠程度最大时，这种方法的性能优于匹配滤波器。利用这种方法还非常易于实现非高斯随机信号的检测。因此，这种检测方法弥补了匹配滤波器必须有先验知识才能达到良好检测效果的不足。     

一种基于非线性变换的EP潜伏期变化自适应检测方法

该文依据分数低阶矩理论和诱发电位（EP）信号及噪声的低阶α稳定分布特性，提出了一种自适应检测EP潜伏期变化的新方法。这种方法基于sigmoid函数对误差信号en(k)进行连续的非线性变换，即抑制了EP信号中的低阶α稳定分布噪声，又有效保留了信号成分，在高斯和低阶α稳定分布噪声条件下具有很好的韧性，且无须动态估计信号噪声的α参数。利用这种方法动态检测EP潜伏期的变化，比以往的DLMS，DLMP和SDA等算法具有较高的估计精度和较快的收敛速度，是一种具有较高韧性的性能优良的EP潜伏期变化动态检测方法。     

振荡器噪声的模拟

模拟由任何一种随机过程、线性频率漂移和日差所引起的钟的时差xn,本文提出了一种方法。随机过程包括:(1)白噪声调相;(2)闪变噪声调相;(3)白噪声调频;(4)闪变噪声调频;(5)随机游动噪声调频。人们选择部分噪声、潜在的日差和线性频率漂移,能恰当地模拟所研究的振荡器,首先,单个地产生出每一种噪声,再把它们点对点的彼此相加,最后,为模拟真实的数据采集系统,要对每一点的数据进行修整。从普通的阿仑方差图上,可以得到每一种噪声类型的噪声电平,xμ和σy2(τμ)允许人们估算作为数字滤波器输人的随机“冲击”的方差。文中给出的特殊的递归函数,能模拟上述五种随机过程,以及线性频率漂移。对此还举了一个典型例子。     

基于主分量分析的噪声压缩技术研究

本文首先提出了客观评价噪声压缩效果的两个指标：残余噪声能量和信号畸变指标。并在此基础上提出了一种基于主分量分析的时间序列噪声压缩方法─噪声压缩链。这种方法充分利用了信号和白噪声之间的统计特征差别，能够有效地压缩时间序列中的白噪声，同时使序列中的信号畸变较小。实例分析结果说明了该方法的有效性。     

闪变信号电路的设计与实现

提出并分析研究一种全数字化技术的闪变信号电路,给出关键电路参数设计准则.闪变信号电路主要由电压取样电路、分频电路、时钟形成电路、相位同步电路和闪变信号产生电路组成.试验结果与理论分析一致.该电路具有输出闪变信号THD小,幅值可调,简单实用,价格低廉等优点,可用作基于SOPC的电压波动和闪变检测与分析的信号,在电能质量研究中具有重要应用价值.     

消除噪声的一种变步长自适应滤波方法

在电子系统中不可避免地会受到噪声的干扰．用固定参数的滤波器进行消除噪声有其缺陷，它对信号与噪声的先验知识需要得较多．本文讨论了用一种变步长自适应滤波器消除噪声的方法．实验仿真证明这种方法能有效地去除弱信号中的噪声．     

振荡器噪声的时─频域滤波

原子钟是振荡器的一种，幂律谱模型是描述原子钟噪声最典型的模型之一，幂律谱模型中的各项具有鲜明的物理意义，将振荡器噪声按其产生的物理机制进行分解，可以对振荡器频率漂移和相位抖动进行实时控制。本文从小波变换的基本原理出发，设计了一种用于噪声分离的时－频域滤波器。这种滤波器可在时频域将信号按不同特征进行滤波，与经典的滤波器相比，在信号空间上不但是相互正交的，而且这个滤波器的结果是唯一的。最后举例说明这种滤波器的应用。     

一种改进的基于ICA的信号增强方法

根据一路带噪信号，采用独立分量分析方法去除加性噪声，从理论上讲就是在观测信号向量的维数小于源信号向量维数情况下的独立分量分析问题。问题的关键是如何构造另一路观测信号，使问题有解。文中提出了一种改进的构造方法，这种方法非常简便，实验结果表明其分离性能比较理想。     

氮化N沟MOS场效应管的界面陷阱特性

一种经过氮化处理背面吸杂的Ｎ沟ＭＯＳ场效应管，在较宽的温度和偏置范围下对其内烁噪声进行测量，将经过不等时间吸杂处理后的器件的噪声能谱进行比较发现，器件经过短时间背面吸杂，其闪烁噪声降低，相长时间吸杂则噪声趋势，探究噪声能量谱与温度的依赖关系表明，器件的低频噪声是由载流子对Ｓｉ－ＳｉＯ２界面陷阱的热激发造成的，而背面吸杂则导致Ｓｉ－ＳｉＯ２的应力衰竭，进而改变了截面陷阱的能量分布。     

Flicker noise in silicon planar transistors

Flicker noise may be characterised by a single parameter ?F, which is the frequency at which flicker noise becomes equal to shot noise. Many devices show ?F to be as low as 60 Hz, and give a noise figure of <1dB at 25 Hz. This is not in accordance with a recently published formula.     

Flicker noise in CMOS transistors from subthreshold to stronginversion at various temperatures

Flicker noise is the dominant noise source in silicon MOSFET's. Even though considerable amount of work has been done in investigating the noise mechanism, controversy still exists as to the noise origin. In this paper, a systematic study of flicker noise in CMOS transistors from twelve different fabricators is reported under various bias conditions corresponding to the gate voltage changing from subthreshold to strong inversion, and the drain voltage changing from linear to saturation regions of operation. The measurement temperature was varied from room temperature down to 5 K. Experimental results consistently suggest that 1/f noise in n-channel devices is dominated by carrier-density fluctuation while in p-channel devices the noise is mainly due to mobility fluctuation     

1/f noise synthesis model in discrete-time for circuit simulation

Flicker noise, popularly known as 1/f noise is a commonly observed phenomenon in semiconductor devices. To incorporate 1/f noise in circuit simulations, models are required to synthesize such noise in discrete time. This paper proposes a model based on the fact that 1/f processes belong to the class of statistically self-similar random processes. The model generates 1/f noise in the time domain (TD) with a simple white noise input and is parameterized by a quantity whose value can be adjusted to reflect the desired 1/f parameter, that is, the slope of the 1/f spectrum. It thus differs from most of the earlier modeling approaches, which were confined to the spectral domain. To verify fit between the model and actual 1/f noise measurements, experiments were conducted using discrete devices such as a PIN photodiode at various bias conditions and sampling frequencies. The noise synthesized by the model was found to provide a good match to the measurements. Furthermore, it is demonstrated that the proposed 1/f noise model can also be incorporated in circuit simulations as a noise current or noise voltage source, which was not feasible earlier with the conventional spectral domain representation. To validate the inclusion of 1/f noise in circuits as TD current or voltage, simulations were carried out on a CMOS ring oscillator and the clock jitter due to 1/f noise was investigated.     

Frequency stability requirements for space communications and tracking systems

Space communications and tracking systems impose stringent requirements on stable frequency sources. "Flicker" (1/f) noise and environmental modulation are two types of oscillator instability affecting typical space systems performance. Examples of several systems are presented with the source requirements for each. Earth satellite systems impose stability requirements of the order of 10^-10over periods of seconds to hours depending on the individual experiment. A typical system requires phase noise of less than 5° rms in a receiver of 12 Hz bandwidth at S-band. An example is presented of a spacecraft transponder which must maintain phase noise below 45° peak-to-peak under vibration of 3g peak from 10 Hz to 10 KHz.     

Noise in a CMOS digital pixel sensor

Based on the study of noise performance in CMOS digital pixel sensor(DPS),a mathematical model of noise is established with the pulse-width-modulation(PWM) principle.Compared with traditional CMOS image sensors,the integration time is different and A/D conversion is implemented in each PWM DPS pixel.Then,the quantitative calculating formula of system noise is derived.It is found that dark current shot noise is the dominant noise source in low light region while photodiode shot noise becomes significantly important in the bright region. In this model,photodiode shot noise does not vary with luminance,but dark current shot noise does.According to increasing photodiode capacitance and the comparator’s reference voltage or optimizing the mismatch in the comparator,the total noise can be reduced.These results serve as a guideline for the design of PWM DPS.     

多元探测红外导引头振动噪声抑制

为了提高红外探测系统的灵敏度,对一种多元探测红外位标器的振动噪声进行了研究。列举了影响红外信号的噪声类型,分析了振动噪声可能产生的各种原因,建立了振动噪声的传递函数,并提出用减振的方法即隔离弹体振动的方法降低位标器的振动噪声。根据此种位标器的特点。建立了减振系统的数学模型,得到位标器振动模型的微分方程并对该微分方程求解。本文的创新点在于运用拉格朗日动力学方程解决了红外系统的振动噪声问题,并在工程中予以成功应用。     

带有均衡因子的反相对称调制法的研究

在对实际通信系统中窄带噪声相关性分析的基础上,介绍了反相对称调制法的系统模型,该模型中信号在两路近似的信道中传输,并在其中一路信道中引入增益因子。论证了该模型中增益因子、两路噪声功率比以及两路噪声相关性这三者的关系,从理论上得出了这三者关系的数学表达式。最后利用MATALAB仿真工具强大的数学仿真功能对这三者的数学表达式进行仿真,从图像上便可直观地验证出反相对称调制法能有效提高信噪比、具有优越抗噪声性能的结论。     

Low-frequency noise in Si0.7Ge0.3 surface channel pMOSFETs with ALD HfO2/Al2O3 gate dielectrics

Low-frequency noise was characterized in Si_0.7Ge_0.3 surface channel pMOSFETs with ALD Al₂O₃/HfO₂/Al₂O₃ stacks as gate dielectrics. The influences of surface treatment prior to ALD processing and thickness of the Al₂O₃ layer at the channel interface were investigated. The noise was of the 1/f type and could be modeled as a sum of a Hooge mobility fluctuation noise component and a number fluctuation noise component. Mobility fluctuation noise dominated the 1/f noise in strong inversion, but the number fluctuation noise component, mainly originating from traps in HfO₂, also contributed closer to threshold and in weak inversion. The number fluctuation noise component was negligibly small in a device with a 2 nm thick Al₂O₃ layer at the SiGe channel interface, which reduced the average 1/f noise by a factor of two and decreased the device-to-device variations.     

CMOS数字像素传感器噪声研究

在研究CMOS数字像素传感器(DPS)噪声特性的基础上,利用脉冲宽度调制(PWM)原理建立了关于PWM DPS完善的系统噪声数学模型。相比于传统CMOS图像传感器噪声研究,该模型考虑了系统中各像素单元积分时间不同和像素级模数转换的特点,推导出总噪声表达式。研究表明,低照度时噪声由暗电流散粒噪声主导,光强大时主要来源为光电二极管散粒噪声。模型中光电二极管散粒噪声与光照无关、暗电流散粒噪声与光照有关。研究结果表明针对PWM DPS系统,适当增大节点电容和比较器参考电压、改善比较器失配可有效降低噪声。