共查询到19条相似文献,搜索用时 125 毫秒
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伪码连续波雷达抑制发射功率泄漏的新技术 总被引:1,自引:0,他引:1
伪码连续波雷达是一种新体制雷达,它采用PN码(m序列)连续波信号形式和脉冲压缩(PC)、脉冲多卜勒(PD)的信号处理技术,大大提高了在现代电子环境中的自卫能力、探测能力.文章研讨了一种抑制发射功率泄漏的新技术,理论分析和计算仿真证明,这种处理方法有极好的抑制发射机泄漏和杂波干扰的能力,并有效地解决了在大多卜勒频移条件下PN码脉压的方法.对量化精度的影响也进行仿真分析. 相似文献
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通过对直扩系统处理增益分析,得到了直扩系统不比未扩频的匹配滤波器数字调制系统具有更强的抗白噪声功能的结论。利用Matlab软件中的Simulink对码分多址误码性能进行了仿真,得到不同用户数与不同PN码长度的误码率关系曲线和不同信噪比与不同PN码长度的误码率关系曲线。结果表明,在相同用户数和同样噪声的情况下,伪码长度越长,其系统误码率越低,证明了GPS军用导航采用长P码使系统具有抗干扰性能。 相似文献
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PN(伪随机噪声)短码规划是CDMA(码分多址)网络设计中特有的问题,良好的PN码规划对于实现设计良好的网络至关重要。通过对同相偏干扰和邻相偏干扰这一对矛盾的分析和处理,介绍了PN码偏置规划的原理以及需要满足的基本条件,并提出了可行的规划方案。 相似文献
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对含噪声直接序列扩频(Direct Spread Spectrum Sequence,DSSS)信号以2倍信息码元2T0时间窗截断计算自相关矩阵并做特征分解,利用最大特征向量对接收DSSS信号的PN码进行盲检测恢复,对最大特征向量求取PN码长累加和、寻找最大值的方法计算PN码在特征向量中的位置。仿真分析表明,该方法能够在低信噪比下对伪随机序列进行估计,同时得到了接收信号中PN码的初始相位。 相似文献
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基于FPGA实现PN码快速捕获方案的设计 总被引:1,自引:1,他引:0
文章基于离散时间信号处理的分析方法,对多普勒频移影响PN码的性能进行了讨论。详细分析了部分数字相关器与FFT结合的频响特性并进行了系统仿真。在此基础上,提出了对存在较大多普勒频移的长伪随机码系统,采用FPGA实现部分数字相关器与FFT频率校正技术相结合的伪码捕获算法,实现较短时间捕获PN码的方案。 相似文献
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一种基于波形的直扩信号伪随机码估计算法 总被引:1,自引:0,他引:1
非合作通信条件下估计未知直接序列扩频信号的伪随机(PN)码是截获直接序列扩频信号信息内容的关键。本文提出一种基于固有时间尺度分解(ITD)的时域波形处理算法,可以在很低信噪比的条件下准确地估计直接序列扩频信号的PN码。该算法充分利用ITD时频分辨率高和适于实时处理的优势,直接分解直扩信号波形,借助于多个周期的伪随机码信号的相干累加提高信噪比,通过对载频处瞬时幅度累加值与第一上过零点频率处瞬时幅度累加值的差分信号波动特性的分析,找到一个PN码周期内相邻码片极性变化的位置,从而揭示PN码,而不必猜测其代数结构。与已有PN码估计算法相比,该算法具有采样精度要求低,对载频估计误差不敏感,适用于各种类型PN码等优势。计算机仿真验证了所提算法的可行性。 相似文献
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扩频码同步是扩频通信系统中特别关键的技术,相位搜索法捕获是扩频码捕获中最基本的方法,硬件实现最简单,在短PN码捕获时有很大的优势.文中在MATLAB平台研究该捕获方法的实现,给出了整个同步过程的仿真模型,各部分的详细参数设置和关键部分的仿真结果.选择长度为31的PN码进行仿真,用5级移位寄存器产生本地PN码序列,不断调整其相位,直到本地PN码与接收的PN码序列初步对齐.仿真结果表明,该模型能够实现31位PN码的正确捕获.捕获时间与本地PN码和接收PN码之间的相位差有关. 相似文献
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介绍了PN(pseudo noise,伪随机噪声)码在CDMA网络中的作用,对导频复用距离进行了分析,并阐述了PN码规划和优化的原理。在此基础上利用MapBasic编程语言,开发了CDMA网络PN码规划和优化系统,实现了CDMA网络PN码的自动规划和优化。 相似文献
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Spread spectrum techniques have become very useful in modern communications. A common spread spectrum technique is to directly modulate a pseudorandom noise (PN) code onto the carrier. Systems employing this technique are called direct sequence (DS) systems. A primary concern with direct sequence systems involves PN code synchronization (acquisition) of the incoming and local signals to within at least one PN symbol followed by a fine alignment (tracking) which must be maintained throughout transmission. This paper is concerned with the PN acquisition aspect of code synchronization. Specifically, a dual threshold sequential detection receiver is analyzed and a general expression is derived which addresses the probability that the sequential detection procedure ceases after an arbitrary number of samples. This expression is needed in order to support a characteristic function approach in deriving acquisition Probability as a function of time which will be the topic of a subsequent paper. 相似文献
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It is shown that the maximum absolute value of cross-correlation between two pseudorandom noise (PN) sequences can be reduced by deleting those dimensions of the code that contribute to high correlations. The cross-correlation of optimum punctured PN codes to length 1023 is numerically computed. 相似文献
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Cantrell R.A. Dudgeon J.E. Hanley W.R. Mott H. 《Electromagnetic Compatibility, IEEE Transactions on》1971,(2):51-56
The autocorrelation function for pseudorandom binary codes is such that these codes are ideal for suppressing unwanted reflections on antenna ranges. The method presented here depends on amplitude modulating the transmitted signal with a maximum-length linear recurring modulo-two sequence (PN code) and correlating it at the receiver with a delayed version of the code. In this way reflections whose path transit times are greater than 1 bit time from the direct path transmission time are reduced in amplitude by a factor inversely proportional to the length of the code word. Also presented is a simple means for generating the maximum-length shift-register codes using delay lines and mixers that makes this method especially practical for most antenna range applications. 相似文献
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We propose a new optical code division multiple access (OCDMA) scheme for reducing multiple access interference (MAI) and enhancing performance for optical subscriber access networks using modified pseudorandom noise (PN)‐coded fiber Bragg gratings with bipolar OCDMA decoders. Through the bipolar OCDMA decoder and the modified PN codes, MAI among users is effectively depressed. As the data are encoded either by a unipolar signature sequence of the modified PN code or its complement according to whether the data bit is 1 or 0, the bit error ratio (BER) can be more improved with the same signal to interference plus noise ratio over the conventional on‐off shift keying‐based OCDMA system. We prove by numerical analysis that the BER of the proposed bipolar OCDMA system is better than the conventional unipolar OCDMA system. We also analyze the spectral power distortion effects of the broadband light source. 相似文献
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Toward code division multiple access (CDMA) communications and data protection, we propose and analyze pseudorandom noise (PN) sequences generated from a 2‐dimensional array structure of shift‐registers. For any positive integers m and n, we construct PN sequences of period 2mn–1 using an m×n array of registers and show that we can generate all shifted PN sequences as required by IS‐95x with the proper linear combination of available sequences. 相似文献
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Multiple-Access Performance Analysis of Combined Time-Hopping and Spread-Time CDMA System in the Presence of Narrowband Interference 总被引:1,自引:0,他引:1
《Vehicular Technology, IEEE Transactions on》2009,58(3):1315-1328
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非合作直接序列扩频系统中伪随机码的估计与同步是正确获取信息的关键。现有的研究成果多集中在短码或周期长码直扩信号的解扩,该文针对无伪码先验知识条件下NPLC-DSSS信号的失步时间估计问题,提出一种基于相关矩阵元素分布建模的方法,该方法以信息码宽分段的信号构建自相关矩阵,并以该矩阵的Frobenius 范数与失步时间之间的对应关系,实现NPLC-DSSS信号失步时间的精确估计。在此基础上,通过引入判决辅助思想构建了循环迭代结构实现了NPLC-DSSS信号伪码序列的盲估计。最后,推导了该伪码序列盲估计问题的Cramer-Rao理论界。数值分析结果表明,文中所述算法在相同的信噪比和数据量条件下具有更好的估计精度,且对伪码的估计性能接近理论界。 相似文献