共查询到20条相似文献,搜索用时 140 毫秒
1.
2.
3.
4.
文章提出了一种新的信号偶,伪随机三元序列偶.首先研究了三元序列偶及其自相关函数的性质,然后讨论研究了伪随机三元序列偶的性质,伪随机三元序列偶存在的充分必要条件,频谱特性.在这些性质的基础上,利用计算机搜索出了若干小体积的伪随机三元序列偶. 相似文献
5.
6.
7.
8.
9.
伪随机三元阵列偶理论研究 总被引:1,自引:0,他引:1
文中提出了一种新的具有良好循环相关特性的离散信号,即伪随机三元阵列偶。首先给出了伪随机三元阵列偶的相关定义;然后研究了伪随机三元阵列偶的变换性质和频谱特性;而且,为了减小搜索范围,提高搜索效率,给出了伪随机三元阵列偶存在的必要条件;最后证明了伪随机三元阵列偶的唯一性,并给出了一种构造伪随机三元阵列偶的方法。 相似文献
10.
11.
超混沌序列对DS-UWB多址性能的改善 总被引:1,自引:1,他引:0
利用Roessler超混沌系统构造了一种新的超混沌序列,分析了序列的相关特性,并将其应用于直接序列超宽带(DS—UWB)系统中,以提高它的误码性能。建立了DS-UWB通信系统的模型,以超混沌序列作地址码对高斯白噪声信道中多用户DS—UWB系统误码率进行了分析,并将其与m序列作地址码时的相应性能进行了比较。由分析和仿真可知,构造的新的超混沌序列能较好地改善DS-UWB的多址性能。 相似文献
12.
水声多径干扰限制了水声直接扩频通信系统的进一步应用,选取性能更好的扩频序列可以提高水声扩频系统的抗干扰性能。在讨论了LS码特性的基础上,提出了将LS码应用于水声直接扩频通信中,并分析了LS码应用的优势。通过多径瑞利水声信道模型仿真,验证了LS码水声扩频通信的良好性能。利用了二次谱和奇异值分解的方法对LS码水声直扩信号的扩频序列进行了估计。仿真结果表明,该方法在信噪比为-11dB时还能准确的估计出LS码。 相似文献
13.
14.
A secure media distribution scheme is proposed in this paper, which distributes different media copy to different customer
in a secure and efficient manner and is able to trace illegal redistribution. At the sender side, media data are scrambled
with a random sequence under the control of a secret key. At the receiver side, the scrambled media data are descrambled with
a new random sequence under the control of a unique customer code besides the secret key. The scrambling and descrambling
strength can be adjusted by the parameter named quantization factor. Generally, the bigger factor is used in scrambling and
the smaller one is used in descrambling. After descrambling, the recovered media copy that contains a unique customer sequence,
named fingerprint, is slightly different from the original one. This difference is imperceptible to human eyes, while can
be detected by computers and used to trace the redistribution of the media copy. Additionally, the unique customer sequence
is produced by the collusion-resistant code, which can survive the attacks that combine several copies by averaging. The scheme’s
performances, including security, imperceptibility, robustness and efficiency, are analyzed and tested in detail. Its good
performances make it a suitable choice for lightweight secure multimedia distribution, such as music download, image sharing,
live TV or video-on-demand, etc., especially over Mobile terminals. 相似文献
15.
Operating Distance Equation and Its Equivalent Test for Infrared Search System with Full Orientation
An operating distance equation of infrared search system with full orientation has been derived for a system design with an infrared point target and with the regular atmosphere condition and objective radiation properties. The traditional operating distance equation of infrared search system is corrected. An equivalent test method of system-operating distance equation is brought forward, if the test conditions are deviated from the regular atmosphere condition and objective radiation properties for the system design. The equation and method can be used to design and test system, and to evaluate comprehensive performances for the infrared search system. 相似文献
16.
本文提出了一种基于连续相位调制(CPM)并用于直接序列扩频多址(DS/SSMA)的新型相位扩谱序列(PSS),以及它的最佳设计准则.依据该准则并在调制指数为0.5的连续相频键控(CPFSK)条件下,通过穷尽搜索法得到了含有若干种不同周期长度的相位扩谱序列的集合.同时在瑞利衰落信道条件下,作者对采用相位扩谱序列的DS/SSMA系统的性能进行了研究,最后将采用PSS序列和传统直扩序列的DS/SSMA系统的性能进行了比较. 相似文献
17.
Multipath dispersion and fluorescent light interference are two major problems in indoor wireless infrared communications systems. Multipath dispersion introduces intersymbol interference at data rates above 10 Mb/s, while fluorescent light induces severe narrowband interference to baseband modulation schemes commonly used such as OOK and PPM. This article reviews the research into the application of direct sequence spread spectrum techniques to ameliorate these key channel impairments without having to resort to complex signal Processing techniques. The inherent properties of a spreading sequence are exploited in order to combat the ISI and narrowband interference. In addition, to reducing the impact of these impairments, the DSSS modulation schemes have strived to be bandwidth-efficient and simple to implement. Three main DSSS waveform techniques have been developed and investigated. These are sequence inverse keying, complementary sequence inverse keying, and M-ary biorthogonal keying (MBOK). The operations of the three systems are explained; their performances were evaluated through simulations and experiments for a number of system parameters, including spreading sequence type and length. By comparison with OOK, our results show that SIK, CSIK, and MBOK are effective against multipath dispersion and fluorescent light interference because the penalties incurred on the DSSS schemes are between 0-7 dB, while the penalty on OOK in the same environment is more than 17 dB. The DSSS solution for IR wireless transmission demonstrates that a transmission waveform can be designed to remove the key channel impairments in a wireless IR system. 相似文献
18.
19.
叙述了PECVD SiN的制备、性能及其在GaAs场效应器件中的应用。第一部分叙述PECVD SiN的一般概念、设备及淀积条件,阐明其键结构以及它们与工艺条件的关系。第二部分叙述PECVD SiN性能及其与工艺条件的关系,着重叙述在GaAs器件中的应用和对器件性能的影响。 相似文献