宽带放大器的设计与制作

该设计放大部分采用集成电路,具有硬件电路形式简单,频带宽,增益高,AGC动态范围宽的特点,且增益可调,步进间隔小。该宽带放大器以可编程增益放大器AD603为核心,由三级放大器组成,前级放大主要是提高输入阻抗,对小信号进行放大;中间级为可变增益放大器,主要作用是实现增益可调及AGC功能,增益控制和AGC功能都由单片机控制,可预置并显示增益值,增益范围-6dB～48dB,步进6dB,后级放大进一步增加放大倍数,扩大输出电流,提升放大器的带负载能力,提高输出电压幅度,范围为10dB~46dB。后级输出接峰值检波电路,检波电路输出由单片机采样并计算后,用液晶显示屏显示输出正弦波电压的有效值。     

GPS低噪声放大器的设计与制作

利用仿真软件ADS,设计仿真了一个GPS的1575MHz频段的低噪声放大器,选用ATF-34143FET作为两级级联结构电路的放大器件,用微带线作为传输线,应用于GPS的天线接收系统中。首先设计稳定电路解决场效应管的稳定问题,然后重点进行匹配电路的设计,最后包括电源电路在内构成一个完整的低噪声放大器电路。制作实物,并进行调试,最后测试结果：增益30．5dB,噪声系数0．7dB,输入输出驻波比优于1．4,增益平坦度带内每5MHz小于0．2dB,1dB压缩点11dBm。     

高增益低功耗CMOS低噪声放大器的设计

本文基于TSMC 0.35μm CMOS工艺,设计了一种工作于2.4 GHz频率下的、高增益、低功耗的低噪声放大器.并在ADS的平台下进行了参数的优化与仿真.其仿真结果表明,该低噪声放大器的最大增益约为16 dB,并且波动范围小于0.3dB;噪声系数约为0.8 dB,IIP3为 1.6 dBm:在1.5 V电源电压供电条件下,电路直流功耗为8 mW.因此,该电路实现了高增益、低功耗的功能.满足实际应用的要求.     

2.4GHz 0.18μm CMOS低噪声放大器分析与设计

基于低噪声放大器设计原理,从噪声、线性度、阻抗匹配等方面详细讨论了低噪声放大器的设计。电路采用TSMC 0.18μm CMOS工艺进行设计,利用ADS2005A对电路进行谐波平衡、S参数分析及双音测试,结果表明,其噪声系数为1.795dB,正向增益为17.35dB,IIP3约为-1.43dBm,功耗约8.96mW。     

一种射频CMOS低噪声放大器的设计

应用TSMC0.35um CMOS工艺模型,设计了可应用于无线通信系统的低噪声放大器(LNA),电路采用单端共源共栅结构,用SmartSpice对电路进行分析优化,仿真结果表明,噪声系数为1.65dB,增益高于20dB。     

宽带低噪声放大器的设计

探讨了使用S参数设计低噪声放大器(LNA)的方法。设计采用了PHEMT晶体管(ATF-35143)。设计过程首先从等效集总元件电路模型设计入手,然后对如何提高电路稳定性,降低噪声系数等方面进行了探讨,最后给出了工作带宽为1650M~2350M,增益G>29dB,增益平坦度GF±1dB,噪声系数NF<0.8dB的两级低噪声放大器的电路仿真结果。     

应用于北斗卫星通信系统的低噪声放大器设计

北斗卫星导航系统由我国自主研发,其研制目的是为了在日益严峻的世界环境下巩固我国的军事实力。北斗射频接收芯片是北斗卫星导航系统中整个地面端设备的核心,因此,关于射频接收机芯片的研发工作具有十分重要且实际的意义。文中在基于窄带低噪声放大器理论的基础上,采用TSMC0．18μmCMOS工艺设计了一种应用于北斗通信系统中的低噪声放大器。放大器采用改进的单转双电路结构,并通过缓冲级电路对差分信号的幅度和相位偏差进行了有效的校正。实验结果表明该电路在2．45GHz-2．55GHz频带内输入回波损耗小于-28dB,噪声系数小于1．1dB,功率增益大于15dB,电压增益高于32dB。     

3GHz～5GHz超宽带噪声系数稳定的低噪声放大器

采用共源共栅级结构和源极负反馈电路设计了一款应用于超宽带系统的低噪声放大器电路。结合巴特沃斯滤波器的特性,实现放大器的输入、输出匹配网络,并详细分析了电路的噪声系数。基于TSMC 0.18μm CMOS工艺,在3 GHz～5 GHz频带范围内对电路进行ADS软件仿真。仿真结果表明,在1.8 V供电电压下,功耗为13.2 mW,最大增益达到15 dB且增益平坦,最大噪声系数仅为1.647 dB,输入反射系数S11<-10 dB,输出反射系数S22<-14 dB。     

以有源电感为负载的CMOS宽带LNA设计

本文设计了一个基于数字CMOS工艺的以有源电感为负载的宽带低噪声放大器,其中包括了级联型有源电感的优化设计。电路采用共栅结构,用HSPICE进行仿真优化,模拟结果表明电路工作良好,S21达到10dB,电压增益为17dB,满足增益要求;在3dB带宽内,S11在-12￣-17dB之间,完全符合一般通信系统S11<-10dB的要求;NF在3.6至4.9之间。通带的反向隔离良好,大于40dB,S22亦在-14dB以下。     

3 GHz CMOS低噪声放大器的优化设计

基于0.18 μm CMOS工艺,采用共源共栅源极负反馈结构,设计了一种3 GHz低噪声放大器电路.从阻抗匹配及噪声优化的角度分析了电路的性能,提出了相应的优化设计方法.仿真结果表明,该放大器具有良好的性能指标,功率增益为23.4dB,反向传输系数为-25.9 dB,噪声系数为1.1 dB,1dB压缩点为-13.05 dBm.     

Genre as noise: noise in genre

Given a specific information need, documents of the wrong genre can be considered as noise. From this perspective, genre classification helps to separate relevant documents from noise. Orthographic errors represent a second, finer notion of noise. Since specific genres often include documents with many errors, an interesting question is whether this “micro-noise” can help to classify genre. In this paper we consider both problems. After introducing a comprehensive hierarchy of genres, we present an intuitive method to build specialized and distinctive classifiers that also work for very small training corpora. Special emphasis is given to the selection of intelligent high-level features. We then investigate the correlation between genre and micro noise. Using special error dictionaries, we estimate the typical error rates for each genre. Finally, we test if the error rate of a document represents a useful feature for genre classification.     

Multichannel active noise equalization of interior noise

An algorithmic variant of the conventional active noise equalizer (ANE), which independently controls some given frequencies of the primary signal, has been developed and extended to the multichannel case. The modified version of the ANE is named common-error multiple-frequency ANE. A detailed analysis of both multichannel equalizers has been carried out. From a convergence analysis in the frequency-domain, the significance of transducer locations in the behavior of a practical system can be predicted through the matrix of secondary path responses at each frequency. The ANEs steady-state transfer functions from the primary input signal to the noise output have also been developed and compared for different parameter settings and for accurate and inaccurate secondary path estimation. Furthermore, the multichannel extension of both equalizers has been implemented in a real-time active system inside a listening room for multifrequency noise. Useful-size zones of equalization have been binaurally measured by using a head and torso simulator. It was found that the common-error multiple-frequency ANE performs better than the conventional equalizer because it achieves a saving in computational complexity and has smaller overshoot. It can also be implemented in a real controller more easily than the conventional ANE and without showing meaningful differences in the practical results provided.     

图像中的高斯和脉冲混合噪声处理

通常情况下,受脉冲噪声污染的图像采用中值滤波法复原,受高斯噪声污染的图像采用均值滤波法复原.为了去除两者的混合噪声,Lee和Kassam提出了一种改进的均值滤波算法Modified Trimmed Mean(MTM),但是MTM的使用受到了阈值的限制.为了在滤除退化图像中混合噪声的同时能更好地保护图像细节,我们详细分析了MTM滤波的特点,在对MTM进行改进的同时,提出了一种改进的自适应中值滤波算法(统计滤波).该算法无需噪声的先验知识,利用Visual C++自动搜索阈值来实现图像的最佳复原.利用两种客观标准进行评价,实践证明新方法的处理结果优于传统的MTM方法.     

图像中的高斯和脉冲混合噪声处理

通常情况下,受脉冲噪声污染的图像采用中值滤波法复原,受高斯噪声污染的图像采用均值滤波法复原。为了去除两者的混合噪声,Lee和Kassam提出了一种改进的均值滤波算法ModifiedTrimmedMean(MTM),但是MTM的使用受到了阈值的限制。为了在滤除退化图像中混合噪声的同时能更好地保护图像细节,我们详细分析了MTM滤波的特点,在对MTM进行改进的同时,提出了一种改进的自适应中值滤波算法(统计滤波)。该算法无需噪声的先验知识,利用VisualC 自动搜索阈值来实现图像的最佳复原。利用两种客观标准进行评价,实践证明新方法的处理结果优于传统的MTM方法。     

应变计的机械热噪声及噪声抑制

应变式传感器的机械热噪声是由于其应变栅与环境相互作用而产生的随机噪声,它影响传感器的灵敏度和分辨力,并增加测量随机误差,制约着应变式传感器的应用。分析导出应变式传感器机械热噪声的一般形式,并用虚拟仪器技术的软件滤波及归一化处理等方法有效地抑制了噪声,使应变式传感器测试系统的准确度提高了一个数量级,说明虚拟仪器技术的软件滤波及归一化处理是抑制噪声的有效方法。     

Adaptive noise smoothing filter for images with signal-dependent noise

In this paper, we consider the restoration of images with signal-dependent noise. The filter is noise smoothing and adapts to local changes in image statistics based on a nonstationary mean, nonstationary variance (NMNV) image model. For images degraded by a class of uncorrelated, signal-dependent noise without blur, the adaptive noise smoothing filter becomes a point processor and is similar to Lee's local statistics algorithm [16]. The filter is able to adapt itself to the nonstationary local image statistics in the presence of different types of signal-dependent noise. For multiplicative noise, the adaptive noise smoothing filter is a systematic derivation of Lee's algorithm with some extensions that allow different estimators for the local image variance. The advantage of the derivation is its easy extension to deal with various types of signal-dependent noise. Film-grain and Poisson signal-dependent restoration problems are also considered as examples. All the nonstationary image statistical parameters needed for the filter can be estimated from the noisy image and no a priori information about the original image is required.     

Nonlinear feedback active noise control for broadband chaotic noise

Feedback active noise control has been used for tonal noise only and it is impractical for broadband noise. In this paper, it has been proposed that the feedback ANC algorithm can be applied to a broadband noise if the noise characteristic is chaotic in nature. Chaotic noise is neither tonal nor random; it is broadband and nonlinearly predictable. It is generated from dynamic sources such as fans, airfoils, etc. Therefore, a nonlinear controller using a functional link artificial neural network is proposed in a feedback configuration to control chaotic noise. A series of synthetic chaotic noise is generated for performance evaluation of the algorithm. It is shown that the proposed nonlinear controller is capable to control the broadband chaotic noise using feedback ANC which uses only one microphone whereas the conventional filtered-X least mean square (FXLMS) algorithm is incapable for controlling this type of noise.     

基于相似性噪声检测的边缘保护滤波算法

为了改善受脉冲噪声污染的图像的滤波效果,提出了一种新的滤波算法。该算法包括3个阶段,首先,利用像素点之间的相似性来检测图像中受噪声污染的像素点;然后,将滤波窗口分为8个主要方向来确定边缘方向;最后,针对噪声点进行边缘保护滤波。实验结果表明,在噪声污染度较小的情况下,该算法不仅能准确地检测出噪声点,而且更多地保护了噪声图像的边缘部分以及非噪声点,具有良好的滤波效果。     

Ensemble-based noise detection: noise ranking and visual performance evaluation

Noise filtering is most frequently used in data preprocessing to improve the accuracy of induced classifiers. The focus of this work is different: we aim at detecting noisy instances for improved data understanding, data cleaning and outlier identification. The paper is composed of three parts. The first part presents an ensemble-based noise ranking methodology for explicit noise and outlier identification, named Noise- Rank, which was successfully applied to a real-life medical problem as proven in domain expert evaluation. The second part is concerned with quantitative performance evaluation of noise detection algorithms on data with randomly injected noise. A methodology for visual performance evaluation of noise detection algorithms in the precision-recall space, named Viper, is presented and compared to standard evaluation practice. The third part presents the implementation of the NoiseRank and Viper methodologies in a web-based platform for composition and execution of data mining workflows. This implementation allows public accessibility of the developed approaches, repeatability and sharing of the presented experiments as well as the inclusion of web services enabling to incorporate new noise detection algorithms into the proposed noise detection and performance evaluation workflows.     

噪音强度的估计和去噪效果的评估

若图像有较大的噪音,会影响视觉效果和有效信息的提取.常用的去噪方法在实际应用中都需要借助图像噪音强度去估计或控制去噪的效果.目前,我们常用的噪音强度估计方法中,没有考虑边缘像素点的影响,使估计值不很准确.把图像的边缘提取与噪音强度的估计相结合,提高了噪音强度估计的精度,并由此导出了去噪效果评估的一个新的数值客观标准算法,该评估方法不依赖在现实中不可知的标准图像,通过实验可以看出该标准具有很大的实用价值.