共查询到20条相似文献,搜索用时 453 毫秒
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该文首先对直接序列扩频技术进行了概述,接着对直接序列扩频系统的处理增益及直接序列扩频技术和多径问题进行了阐述,最后分析了直接序列扩频与窄带相比的优点及多码直接序列扩频技术(MC-DSSS)。 相似文献
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给出了DS-CDMA(直接序列扩频-码分多址)系统中的接收信号模型,在对时域处理和传统Rake接收机分析的基础上,阐述了智能天线和Rake接收机相结合的2-D Rake接收机的概念和原理,并对两种接收机的输出信噪比进行了比较,结果表明在CDMA系统中采用时空信号综合处理的2-D Rake接收机容量和性能将有大幅提高. 相似文献
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在MATLAB平台上,对直接序列扩频系统进行仿真分析.系统采用Hadamard序列作为扩频码,对系统在平坦衰落和瑞利衰落信道环境下的误码率进行分析,讨论了扩频、解扩过程.此外,还仿真比较了不同用户数和不同扩频码的系统,为分析设计直扩系统提供依据.仿真结果表明,本实验系统可在SNR为-1.6dB的传输条件下得到10-3量级的误码率,Hadamard序列可用作扩频序列,系统可用作检验各种正交码组的正交性. 相似文献
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基于通用天线近远场测试系统,给出了系统扩频设计和工程应用的思路,并分别对扩频系统的本振相参、上下变频的一致性进行了论述。实现了Ka频段以下的平面近场、远场天线测量系统的扩频与应用,并给出了8单元EHF频段阵列天线在不同测试系统下的天线测试方向图。测试结果表明,经扩频的测试系统方向图测量数据与毫米波天线测试系统直接测量的结果吻合,说明扩频系统能够满足毫米波天线方向图的测试需求,并具有较高的测试精度,且设计成本较低。同时还具有一定的通用型,对天线的毫米波扩展测试具有较好的工程应用价值。 相似文献
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直接序列扩频技术在现代无线通信系统中有着广泛的应用,该信号的数字接收是实现对其侦察截获的关键技术之一。本文介绍了直接序列扩频技术原理及其在cdma2000移动通信系统中的应用,提出一种针对cdma2000直接序列扩频信号的零中频数字接收算法,并详细给出了码捕获及跟踪算法、载波同步算法的数学模型推导。实验结果显示,该算法成功地实现了码同步及载波同步,有较好的解调效果。 相似文献
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The results of a preliminary study suggest that interference to the downlink of one geostationary satellite from that of another satellite in the adjacent orbital slot can be substantially reduced by the addition of a simple adaptive nulling system to the ground terminal antenna. Alternatively, the nulling system allows the satellites to be spaced significantly closer together with no increase in interference. Significant improvement is obtained with simple open-loop antenna pointing. The improvement is greater, however, if the adaptive antenna automatically tracks the direction of the desired source. For a dish antenna with a single receiving feed horn, the extra hardware required to provide the adaptive capability consists of two more receiving feed horns, a variable weighting device for each of the feed lines (now three in number) and the adaptive control electronics. An example shows that the minimum spacing between one satellite and an interfering satellite, consistent with certain assumed operating requirements, could be reduced from the2.25deg needed for a simple single beam antenna to1.35deg , for the adaptive antenna using open loop pointing, to as little as0.7deg , for the adaptive antenna using automatic pointing. The adaptive hulling also provides essentially the same protection against downlink interference from the two other satellites occupying the slots on both sides of the satellite serving the terminal. The three degrees of freedom of the postulated nulling system, however, cannot cope with three or more nearby interfering satellites. 相似文献
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功率倒置算法不需要知道接收信号的先验信息,能够使天线产生指向干扰方向的波束零陷,达到抑制干扰的目的。特别适合卫星导航、扩频通信等强干扰、弱信号环境的抗干扰应用。在对功率倒置自适应算法原理分析的基础上,利用LMS算法迭代计算功率倒置的最优权值,然后针对四阵元天线仿真了功率倒置算法在不同干扰条件下的抗干扰性能,以及迭代步长等因素对算法收敛性能的影响,验证了功率倒置算法的自适应抗干扰性能,从而为后续硬件工程实现奠定了基础。 相似文献
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为了提高卫星导航接收机抗干扰能力,深入研究了应用于卫导自适应调零天线的多线性约束自适应调零算法。对现有功率倒置自适应算法进行改进,将阵列协方差矩阵分为干扰子空间和噪声子空间,通过对子空间的处理提高输出信干比,在不是很强的干扰信号方向上也形成较深"零陷"。此外,为了降低计算的难度,避免自相关矩阵求逆,采用了陡降算法。通过仿真分析,结果表明:所研究的自适应滤波算法能够提供较高的输出信干比,在干扰信号方向产生较深的"零陷",具有较好的干扰抑制能力。 相似文献
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Presents a case study of the design of a computationally intensive system to do adaptive nulling of interfering signals for a phased-array radar with many antenna elements. The goal of the design was to increase the computational horsepower available for this problem by about three orders of magnitude under the tight constraints of size, weight and power which are typical of an orbiting satellite. By combining the CORDIC rotation algorithm, systolic array concepts, Givens transformations, and restructurable VLSI, we built a system as small as a package of cigarettes, but capable of the equivalent of almost three billion operations per second. Our work was motivated by the severe limitations of size, weight and power which apply to computation aboard a spacecraft, although the same factors impose costs which are worth reducing in other circumstances. For an array of N antennas, the cost of the adaptive nulling computation grows as N3, so simply using more resources when N is large is not practical. The architecture developed, called MUSE (matrix update systolic experiment) determines the nulling weights for N=64 antenna elements in a sidelobe cancelling configuration. After explaining the antenna nulling system, we discuss another DSP computation that might benefit from similar architecture, technology, or algorithms: the solution of Toeplitz linear equations 相似文献