海洋激光雷达系统的噪声相空间重建的研究

通过对混沌信号以及海洋激光雷达接收信号噪声的相空间分析,探讨了由时间序列重构相空间时参数选择的影响。重建了确定信号、随机信号、混沌信号和海洋激光雷达接收信号噪声的相空间。经过以上工作,初步掌握了重构相空间时参数选择的规律,明确了确定信号、随机信号和混沌信号各自的相空间特性,并发现海洋激光雷达接收信号噪声与混沌信号有相似的相轨迹。     

一种降低OFDM系统PAPR的低复杂度算法

选择映射(SLM)是一种无失真降低OFDM信号峰平比(PAPR)的有效方法,但该方法通过串并转换将一路信号变为U路信号,再对U路信号进行IFFT处理,计算量大,同时也降低了信号传输速率。文中提出了一种改进的随机筛选法方案,该方法在IFFT模块之前就对序列进行选择,根据判决门限选择其中随机性最好的一路信号进行传输。其与SLM法相比,只进行一路信号的IFFT计算,复杂度大幅降低,且提高了信号传输效率,并在较大程度上降低了OFDM信号的峰平比。     

一种引入退火降温阈值函数约束的改进MP稀疏分解方法

匹配追踪(Matching pursuit, MP)方法可以在过完备库中实现信号的稀疏、能量集中的分解。该文从对信号分解稀疏性的有利原则出发,在迭代过程中,将过完备库划分为新(未选择过的)、旧(已选择过的)原子库,通过引入退火降温阈值函数来约束迭代过程中最优原子的选择,使选择的最优原子比原始MP方法有更大的可能性落入对信号稀疏性有利的旧原子库中,从而实现对信号更加稀疏的分解。对余弦调制指数信号和一段语音信号的分解结果,证实了改进MP方法对信号有更加稀疏的分解结果。     

基于数据分类思维的网络危险信号检测系统设计与实现

传统网络危险信号检测方法,需要对网络的全部数据包进行挖掘,导致所用检测时间长,空间复杂度高,无法准确地检测出网络危险信号。设计并实现了一种基于数据分类思维的网络危险信号检测系统,该系统包括预处理模块、特征选择模块、信号分类模块等。通过分数阶傅里叶变换对网络危险信号进行预处理操作。采用网络信号特征选择的方法,对已经完成预处理的网络信号进行特征选择。再通过半监督聚类算法从大量混乱无序的网络信号特征中获得训练数据集,并进行组合信号分类器分类。基于学习结果分析是否存在网络危险信号,实现网络危险信号的准确检测。实验结果说明,所设计系统对于网络危险信号的检测效率、误报率都优于人工免疫系统,具有较高的应用性和实时性。     

前置放大器

前置放大器是指把音频（AUX、MIC）信号放大至功率放大器所能接受的输入范围,其功能有两个：一是要选择所需要的音源信号,并放大到额定电平;二是要进行各种音质控制,以美化声音。前置放大器的基本组成有：音源选择、输入放大和音质控制等电路。音源选择电路的作用是选择所需的音源信号送入后级,同时关闭其他音源通道;输入放大器的作用是将音源信号放大到额定电平,     

新奥特非线性编辑系统应用技巧

许多用户在使用非编时经常会遇到一些问题,下面选取几个问题予以解答: 问题1:输出复合信号时,发现输出的画面是黑白的? 解答:和采集素材一样,对于输出的视频信号也需要做出必要的设置,具体方法是:打开“控制面板”,双击DigiSuite图标,选择DigiSuiteDTV(L或LX等),单击Video Out,选择Program Out后,有两个可以选择的项目,分别是Composite(复合信号),Y/C(S—Video)(Y/C信号),SDI(数字分量信号)和Analog Component(模拟分量信号),用户可根据自己的需要选择复合信号或分量信号的输出。     

一种非平稳信号的DOA估计方法

利用空时频分布(STFD)矩阵估计非平稳信号DOA的关键是选择合适的时频点。用白化后的接收信号矢量构造STFD矩阵,利用该矩阵迹构造判决量来选择时频图的自项,将选择的自项的STFD矩阵平均,然后运用MUSIC算法来估计DOA。仿真证明:本文的方法可以很清晰的选出非平稳信号的自项,运用该自项点的平均STFD矩阵估计的信号DOA更准确。     

康佳P2993N型画中画镜面彩电主要集成块维修参数

表1.微处理器NA01(C},J叫003S)功 能子画面对比度控制输音量控制输出子画面消色信号输出拉OK音效输入与控制(该机此功能未用,均为空脚)子画面50/60Hz转换控制无信号静噪控制予画面行同步控制子画面PAL/N’TSC制式识别控制子画面色副载波选择控制AFT信号输入定时指示控制键扫描信号输出伴音制式选择l伴音制式选择2伴音制式选择3伴音制式选择4/NTSC制式开关50/60Hz切换控制接地端屏显红色字符信号输出屏显绿色字符信号输出屏显蓝色字符信号输出屏显字符消隐信号输出屏显行同步信号输人屏显场同步信号输入屏显字符振荡器l屏显字符振…     

傅里叶变换与小波变换在信号去噪中的应用

对于高频信号和高频噪声干扰相混叠的信号,采用小波变换去除噪声可以避免用傅里叶变换去噪带来的信号折损。对于噪声频率固定的平稳信号,在对信号进行傅里叶变换后使用滤波器滤除噪声。对高频含噪信号则采用正交小波函数sym4对信号分解到第4层,利用极大极小值原则选择合适的阈值进行软阈值处理,最后利用处理后的小波系数进行重构。实验结果表明,对于高频含噪信号傅里叶去噪会出现严重的信号丢失现象,使用极大极小值原则选择阈值进行小波去噪可以有效地保留高频部分的有用信号。     

线性调频与相位编码混合雷达信号处理仿真

为了保证雷达系统能够在复杂的电磁环境中有效地工作,雷达信号的选择尤为重要。本文采用线性调频信号与相位编码信号相结合的码内线性调频信号作为雷达信号,针对这个信号进行了整个雷达信号处理的仿真。仿真结果表明,码内线性调频信号具有较好的抗干扰的特性。     

视音频智能切换开关

针对我台需对多路视音频信号进行检测、倒换的要求,介绍了对一种四选一信号手动切换器进行改进,使其具有视频信号检测功能和自动切换功能。     

New retiming and synchronisation scheme for optical ATM switching systems

A new signal format and retiming method for optical ATM switching systems is proposed. An input signal is transformed to an optical signal with a unique word as a guard time for switching. A common optical receiver can be used for bit synchronisation, and logic gates can achieve cell synchronisation using this new optical signal format.<>     

Effect of Time Lag in Response to Switching Signal in Interrupted Electric Circuit

In this study, we analyze the characteristics of an interrupted electric circuit. In particular, we focus on a special situation where the switching action of the circuit is delayed because of a time lag in the response to the switching signal. This situation is observed in switching circuits driven by a high-frequency switching signal. However, the fundamental characteristics of this type of circuit have not yet been clarified. To address this shortfall, we assume that a time lag of the response to the switching signal occurs in simple interrupted electric circuits, and investigate how this time lag affects circuit characteristics. First, we show the model of a circuit whose switching action is the same as that of a current-mode-controlled dc/dc converter. Here by using logic circuits, we impose an artificial time lag on the response to the switching signal. Next, we define a sampled data model (i.e., a return map) that we analyze in detail. Based on the return map, we derive one- and two-parameter bifurcation diagrams. Finally, we compare the bifurcation diagrams constructed with time lag to those constructed without time lag. The results clearly show that time lag is responsible for a new structure in the return map that does not occur in circuits with ideal switching. This new return map structure is a key to understanding the essential characteristics of circuits with time lag. Furthermore, the mathematical results are verified experimentally.     

Impairment-aware ordered scheduling in dual-header optical burst switched networks

Optical burst switching (OBS) is a promising technology for bridging the gap between optical wavelength switching and optical packet switching. Optical signal transmission quality is subject to various types of physical impairment introduced by optical fibers, switching elements, or other network components. The signal degradation due to physical impairment may be significant enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal to not usable. In this article, based on earlier study, we study the burst-scheduling problem in OBS networks using two control packets for each data burst, taking into account physical impairment effects. We propose a burst-scheduling algorithm that accommodates incoming bursts by primary path routing, deflection routing, and burst scheduling. We design an admission control mechanism to use network resources efficiently. At an OBS node, the proposed algorithm schedules bursts for transmission by searching for available resources as well as verifying signal quality. Our simulation results demonstrate that the proposed algorithm is effective in terms of reducing the burst-blocking probability.     

全光网中光码流性能的整体监控

波分复用(WDM)多粒度交换可重构全光网是当前光通信网发展的方向,该文构造了一种实际试验网,提出了一种 眼图法对网中数字光信号进行全面监控的方法,并在自建WDM多粒度交换可重构全光网试验床上进行了演示,结果显示在网络重构等各种条件下均可对网中各波长通道数字信号的信噪比、定时抖动、功率、误码率等进行实时监测控制,该方法对光信号的协议和速率透明且能对各种光性能劣化进行鉴别。     

Linearization and feedforward compensation for switching systems

The linearization of a switching system including a feedforward compensation for power supply perturbations is obtained by the addition of a high-frequency signal. A general expression for the required shape and amplitude of this high-frequency signal is derived. The method is analyzed for its application to AC phase control systems. The method is outlined for the case of a DC electric motor phase control. It is then generalized to any nonlinear switching system     

适用于TTL数字电路元件级设计的开关—信号理论

本文分析了以布尔代数为基础的数字电路设计的不足，提出了将开关状态和信号这二类变量分别描写的观点，讨论了ＴＴＬ电路中晶体管开关元件与信息之间的相互作用过程，在此基础上，建立了适用于ＴＴＬ电路的限幅电压开关理论，设计实例说明，该理论能有效地指导各类ＴＴＬ电路在元件级的逻辑设计。     

A compact digital beamforming SMILE array for mobile communications

A compact spatial multiplexing of local elements (SMILE) scheme smart antenna array with adaptive beamforming is presented. Low-noise amplifiers are implemented as switching elements to maintain a low system noise figure and allow fast switching. The switching scheme effectively reduces N RF channels to one, reducing the amount of costly RF hardware by a factor of N. The sampling rate must be higher than the signal bandwidth based on the Nyquist criterion to ensure proper restoration of the original signal. Measured data for destination of arrival estimation, beamforming, and digital data recovery demonstrate the capability and benefits of digital beamforming with this architecture.     

混沌频率调制增强开关变换器EMC的研究

探讨了混沌频率调制技术在开关变换器中抑制电磁干扰的实际效果.分析了被调制信号的频谱与混沌系统产生的调制信号的不变密度函数之间的关系.设计了一个简单的Ber noulli映射混沌电路,并加入到工作在双环控制模式的Boost变换器,使开关频率随机变化.实验结果证明了提出的技术能有效降低开关变换器的谐波峰值和应用于开关变换器的可行性.     

Variable-bandwidth filters using switching

It is shown that, if a switching technique is used to scale the bandwidth of a lowpass filter, the resultant circuit has some of the characteristics of an N-path filter. The consequence of this is that the signal frequency must be bandlimited to avoid spurious responses at the switching frequency and its harmonics.