西门子SL55德国巨人的复苏

S57的推出让人看到了西门子振兴高端产品线的希望．但单凭一款产品就想重新唤起人们的注意那肯定是不够的，而深明此理的德国巨人在今年6月份终于把旗下最新秘密武器——SL55亮相世人，下面就和大家一起领略一下这款手机的过人之处。     

恒生SL—2000增强型

配置上具有一定的优势,设计也为使用者带来不少方便,并提供了比较多的功能,如果在系统上精练一些,价格上将更具优势。     

基于SL811的嵌入式USB主机设计

本文介绍了使用SL811作为接口芯片的USB主机的设计方法。该系统抛开了PC机,把USB主机引入到嵌入式系统中,拓展了USB的应用领域。程序代码绝大部分与硬件无关,更具有可移植性。     

300MHz一次变频接收机SL6609的应用

上文曾对ＳＬ６６０９的基本工作原理作以介绍。而产品的研发者更感兴趣的芯片如何在实际电路中的应用，下面的篇幅主要展开介绍这一芯片在应用电路中的要点。     

德国工艺 隽永品味——西门子SL

SL75选择五月天组合的石头做代言，广告语就是“石头的石头机”。一开始我们很不理解，总觉得这该是款更偏重女性的手机，但看到宣传画恍然大悟，曾经如此暴躁的石头，含情脉脉地捧着SL75。想想他从一个野蛮小子到顾家男人的转变，诠释着SL75是为那些善解人意、被人呵护的幸福女性准备的精致礼物。圆润顺滑的外形，细致宜用的功能，强大的媒体表现，这款手机将成为众多女性最新的追捧对象。     

一类高斯色噪声信号的谱特性与生成

仿真无线时变信道的衰落特性常常需要具有一定功率谱形状的色高斯噪声信号。本文推导了无线信道快衰落特性的功率谱及其受限功率谱,分析了宽带高斯过程的谱特性和时间相关性,同时考察了具有高斯功率谱形状的信道阴影慢衰落的特性。通过有限正弦信号叠加近似生成了宽带色高斯噪声信号,确定了正弦分量的多普勒频率和多普勒系数。     

由Signless Laplacian谱确定的一类奇单圈图

为了探讨一类奇单圈图的Signless Laplacian谱惟一的的问题,利用图与其线图之间的关系,图与其多项系数之间的关系以及图与其同谱图之间的关系,证明了Signless Laplacian同谱图的一个重要的的结构,即:恰含一个奇单圈图的Signless Laplacian同谱图也是一个连通奇单圈图。在此基础上证明了一类奇单圈图的Signless Laplacian谱惟一性,确定了此类奇单圈图的结构。     

图和线图的邻接谱及拉普拉斯谱的关系

图谱理论是图论研究的重要领域之一,也是非常活跃的研究方向。实践表明,对特征值的计算十分复杂,但可以研究不同定义的谱之间的关系确定特征值的上下界。通过利用对称矩阵和半正定矩阵的一些性质,讨论简单无向图G及其线图Gl的邻接谱之间的一些关系,推广已有的结果。同时也讨论图的邻接谱和拉普拉斯谱之间的关系。对判定某些图的邻接谱和拉普拉斯谱的范围具有一定的指导作用。     

基于空间谱的多天线盲频谱感知算法

现有的频谱感知算法主要在时间、频率以及地理空间维度进行检测,对角度维的利用尚不成熟。将多天线技术中的到达角（AOA, angle of arrival）估计算法应用到频谱感知领域,提出了2种基于空间谱的盲频谱感知算法,分别为最大—最小延迟相加谱值比检测和平均—最小延迟相加谱值比检测。利用空域匹配滤波的优势,新算法在低信噪比下得到了较高的检测概率,同时为角度维的频谱接入提供了AOA信息,从而提高了频谱利用率。此外,运用随机矩阵理论,推导了检测阈值和检测概率的理论值。仿真结果表明,在Nakagami-m信道下,提出的算法具有比现有盲感知算法更优的检测性能。     

Correlation-and-bit-aware additive spread spectrum data hiding for Laplacian distributed host image signals

Watermarking and data hiding are important tools for copyright protection of digital media contents. To reduce the interference effect of the host signal and improve the decoding performance in the popular additive Spread Spectrum (ASS) embedding scheme, we have proposed a novel correlation-and-bit-aware additive Spread Spectrum (CASS) embedding scheme for the Gaussian distributed host signal. However, in practice, the discrete cosine transform (DCT) coefficients of real images follow the Laplacian distribution. For practical application of CASS to real images in the DCT domain, this paper proposes a CASS data hiding scheme for the Laplacian distributed host image signal. To extract the hidden message bits, we derive an optimal decoder of the ASS scheme for the Laplacian distributed host signal. The bit-error ratio (BER) of ASS and proposed CASS schemes are analyzed in theory. Finally, Monte Carlo simulations and tests on real images are carried out to illustrate the decoding performance of the ASS and proposed CASS schemes. Compared with the traditional ASS scheme, the proposed CASS scheme maintains the simplicity of the decoder, significantly reduces the host effect in data hiding and improves the decoding performance remarkably. As an extension, we discuss the CASS scheme for the generalized Gaussian distribution (GGD) distributed host signal in brief.     

Fusion spectrum sensing algorithm based on eigenvalues

Aiming at the problem of inefficient use of spectrum resources,a fusion spectrum sensing algorithm based on eigenvalues was proposed to effectively achieve dynamic spectrum sharing.The test statistics were constructed by employing the maximum eigenvalue,the trace and the geometric mean of all eigenvalues of the sample covariance matrix.The detection probability and false alarm probability of the proposed method were analyzed using the random matrix theory,and the analytical representation of the theoretical threshold was obtained.In addition,the parameter selection of the proposed algorithm was analyzed theoretically.Simulation results show that the proposed algorithm has better detection ability than the existing eigenvalue detection algorithm.     

可移动基站网络频谱资源块动态分配方法研究

首先从应用需求,引出了移动式基站的概念,然后设计了一种针对该网络资源分配的优先级策略并从提 高资源利用率和降低频谱重分配次数2个角度出发,提出了2种基于图论的资源分配策略,最后完整地提出了一 种低复杂度的分布式频谱资源块动态分配算法。仿真结果表明,所提算法有良好的性能。     

Cooperative blind spectrum sensing using autocorrelation matrix

To improve the spectrum sensing performance in cognitive radios, a scheme of cooperative blind spectrum sensing based on autocorrelation matrix is proposed. The test statistic is extracted from the autocorrelation matrix of the received signal samples and a bi-threshold hybrid decision scheme is designed for local spectrum sensing. The cognitive radio base station makes a credibility fusion based on the local soft decisions and then takes global fusion combining with the local hard decisions. The proposed method is blind in the sense since it requires no apriori knowledge of the signal and the noise power. Theoretical analysis and computer simulation results show that the proposed method can enhance the spectrum sensing capability.     

小波谱及其在线性调频信号检测中的应用

在前人工作的基础上,选用了高斯线调频小波作为基函数,研究了信号的小波谱,给出了小波谱在时间域及频率域的平滑谱并与傅里叶谱进行了比较.线性调频信号的检测与参数估计是一个广泛受到关注的问题,分析了线调频信号的小波变换,并提出了基于小波谱的线性调频信号检测的算法.     

Product spectrum matrix feature extraction and recognition of radar deception jamming

A deception jamming recognition algorithm is proposed based on product spectrum matrix (SPM). Firstly, the product spectral in the different pulse repetition interval (PRI) is calculated, and the product spectral of frequency-slow time is arranged into a two-dimensional matrix. Secondly, non-negative matrix factorisation (NMF) is used to extract the features, and further the separability of the characteristic parameters is analysed by the F-Ratio. Finally, the best features are selected to recognise the deception jamming. The experimental results show that the average recognition accuracy of the proposed deception jamming algorithm is higher than 90% when SNR is greater than 6dB.     

动态频谱分配的连通分支并行处理

快速无干扰的动态频谱分配是实现认知无线电的关键技术之一。针对现有图论频谱分配算法均存在时间开销过大这一瓶颈问题,引入并行原理和连通分量理论,提出了一种连通分支并行处理新方法。该方法可应用于目前所有基于图论着色模型的分配算法,在保证算法原有效益的基础上,能够显著降低频谱分配过程的时间。研究了连通分支并行处理方法的应用实例,结果验证了该方法是快速有效的,更加适应时变的认知无线电环境。