调幅系数为任意值的调幅波研究

本文讨论了调幅系数为任意值的调幅波，给出了它的表达式，频谱与调幅系数，调制效率和信噪比增益的计算公式。     

微光CCD摄像器件综合特性的分析与比较

ＣＣＤ的优良特性使其在微光电视技术领域得到了广泛运用。本文对各种微光ＣＣＤ摄像器件的综合特性例如信噪比、探测率、动态范围与计数模式等进行了详细的研究与对比，并得出基本结论。     

一种基于高阶统计信息的信噪比估计改进算法

针对多进制正交幅度调制(Multiple quadrature amplitude modulation,MQAM)信号在低信噪比条件下估计精度不高的问题,提出了一种基于综合利用高阶统计信息的信噪比估计改进算法。根据所选高阶统计量最高阶数的不同,建立了3种信噪比与多种高阶统计量运算式之间的线性关系,利用全回归线性分析方法将3种线性关系转化为3种全回归模型,并求解模型系数。该算法充分利用了多种高阶统计量的有用信息,提高了信噪比估计精度。MQAM的仿真结果表明:在低信噪比条件下,该算法减小了信噪比估计误差,其估计性能明显优于传统的其他算法,且3种模型估计性能依次增加,可依据不同的信噪比要求对3种模型进行选取。     

Effective DOA Estimation Under Low Signal-to-Noise Ratio Based on Multi-Source Information Meta Fusion

Efficiently performing high-resolution direction of arrival (DOA) estimation under low signal-to-noise ratio (SNR) conditions has always been a challenge task in the literatures. Obvi-ously, in order to address this problem, the key is how to mine or reveal as much DOA related in-formation as possible from the degraded array outputs. However, it is certain that there is no per-fect solution for low SNR DOA estimation designed in the way of winner-takes-all. Therefore, this paper proposes to explore in depth the complementary DOA related information that exists in spa-tial spectrums acquired by different basic DOA estimators. Specifically, these basic spatial spec-trums are employed as the input of multi-source information fusion model. And the multi-source in-formation fusion model is composed of three heterogeneous meta learning machines, namely neural networks (NN), support vector machine (SVM), and random forests (RF). The final meta-spec-trum can be obtained by performing a final decision-making method. Experimental results illus-trate that the proposed information fusion based DOA estimation method can really make full use of the complementary information in the spatial spectrums obtained by different basic DOA estim-ators. Even under low SNR conditions, promising DOA estimation performance can be achieved.     

An approach for minimizing a quadratically constrained fractional quadratic problem with application to the communications over wireless channels

Studies for the cognitive model are relatively new in the literature; however there is a growing interest in the communication field nowadays. This paper considers the cognitive model in the communication field as the problem of minimizing a fractional quadratic problem, subject to two or more quadratic constraints in complex field. Although both denominator and numerator in the fractional problem are convex, this problem is not so simple since the quotient of convex functions is not convex in most cases. We first change the fractional problem into a non-fractional one. Second, we consider the semi-definite programming (SDP) method. For the problem with m (m≤2) constraints, we use the SDP relaxation and obtain the exact optimal solution. However, for the problem with m (m>2) constraints, we choose the randomization method to gain an approximation solution in the complex case. At last, we apply this method to practical communications over wireless channels with good results.     

多天线智能分集接收系统的设计

通过对多天线分集接收技术的分析,针对多径传输引起的衰落,提出一种多天线分集接收方法。本文将智能控制处理技术与空间分集接收天线技术相结合,通过智能控制选择合并算法。通过无线遥控接收机进行实验,取得良好接收效果。     

跳频通信系统的建模与仿真

在Matlab/Simulink仿真的平台上,利用跳频通信基本原理,在给定仿真条件下,建立了跳频通信系统模型,对系统进行了仿真,得到了宽带噪声干扰下的误码率信噪比曲线。通过跳频仿真图形前后对比,得出跳频通信系统的抗干扰能力优于传统的定频通信,在现代通信中有更高可靠性的结论。     

高速突发模式光接收机性能分析

针对无源光网络(PON)中上行突发信号的特点,从误码率、信噪比和信道利用率3个方面对直流耦合突发模式光接收机和交流耦合突发模式光接收机的性能作了对比分析.并给出了改善突发光接收机信噪比和信道利用率的实现方案,对高速突发接收方案的设计有较好的指导意义.     

基于小波变换的电能质量监测

针对噪声系数的幅度随着尺度增加而减小的特点,提出了一种改进的基于小波分解层数的波段自适应降噪算法.利用Matlab仿真软件建立了电压暂降的系统模型,运用小波分析的方法对污染白噪声的电压暂降信号进行了时频分析和降噪处理,分析了软硬阈值降噪方法.实验结果表明,该方法通过调整两个可调参数获得较优的小波系数阈值估计,与常见的三种典型算法相比不仅较好地去除了噪声干扰,且信噪比更高,均方误差更小,同时具有更优的信息保全能力.     

CRS共反射面元叠加技术在加蓬地区的应用

CRS共反射面元叠加方法是一种基于非均匀介质,且不依赖于宏观速度模型,由反射面元的位置、倾角、曲率三参数代替叠加速度来刻画反射界面的成像方法。它利用相邻道集数据之间的相似性,尽可能地集中邻域道集的能量参与叠加,从而压制了随机噪声,增强了反射波同相轴的连续性,很好地提高了地震资料的信噪比。加蓬地区的构造复杂、地震采集资料信噪比低,通过CRS共反射面元叠加技术的应用,成像效果较常规地震资料处理方法的成像效果有显著的提高,说明该技术值得在类似复杂区域进行推广和应用。