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许德刚 《电子科学技术评论》2014,(6):614-618
在以民用广播、电视及CDMA等信号为照射源的无源雷达系统中,由于发射信号为连续波信号,直达波和多径信号对雷达回波的干扰很强,影响了目标的检测。为此采用RLS自适应对消处理技术来抑制直达波干扰,针对RLS自适应算法的性能分析,提出了改进RLS自适应处理算法,收到了良好的滤波效果。最后在以广播信号为照射源的实验系统中,根据实际采集的数据进行仿真论证,验证了该方法的可行性。 相似文献
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基于循环相关特性,该文提出了针对线性调频(LFM)脉冲雷达宽带回波Doppler和多径时延联合估计的方法。该方法首先利用雷达回波的循环相关变换,通过多径分量的能量累积估计Doppler频移尺度参数,然后结合发射信号的先验信息构造降阶函数,将回波信号降为多个单频信号,最后利用零频率截面循环谱能够将时间上有重叠的多径回波信号在该截面上分开且分辨率加倍的特性,估计出各多径分量的时延值。该方法只需要一个脉冲信号即可完成Doppler和多径时延的联合估计,对低信噪比噪声有较强的容忍性,能抑制各径相关交叉项的影响,并且具有较高的多径时延估计分辨率。文中给出了计算机仿真实验,仿真结果表明了该算法的有效性。 相似文献
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讨论强直达信号干扰下弹载脉压雷达高度表回波信号接收问题。在脉压前设置自动增益控制及限幅电路,根据回波信号电平大小及时延长短,在保证回波信号相位特性的同时,对直达信号进行适当限幅,抑制其电平。在脉压后再设置自动增益控制及限幅电路,进一步抑制直达信号压缩脉冲主瓣电平。该技术可有效提高强直达信号干扰时近距离回波信号的检测灵敏度,使雷达高度表具备0~15km的测高能力。 相似文献
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通过对实际CDMA前向信道的分析,得出符合广义RAKE(G- RAKE)接收机的发射信号形式,证明了当多径相对时延非单位扩频码片时G -RAKE接收机多余分支的放置位置。对Matlab中simulink产生的CDMA前向信道信号进行仿真,结果显示了G- RAKE接收机良好的性能。 相似文献
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针对全球卫星导航系统(Global Navigation Satellite System,GNSS)中的多径干扰抑制问题,本文提出了一种有效的算法,该算法首先对接收到的数据进行捕获,以获得各卫星信号的参数粗估结果,接着利用WRELAX(Weighted RELAXation)技术,在空时二维空间中逐一估计出直达卫星信号和多径干扰的来向、码时延和幅度信息;并根据所估计到的参数来区分多径干扰和直达信号;此外,本文在进行二维参数估计时,根据捕获到的码时延的信息,限定码时延的搜索范围的方法显著降低了算法运算量.由于空时二维处理能够同时从空域和时域区分直达卫星信号和多径干扰,因此能够更好地实现多径干扰抑制.最后,通过仿真实验验证了本文算法较之传统多径干扰抑制算法的优越性. 相似文献
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本文通过案例形式,结合CDMA掉话机制及OMC现网运行数据,从前向功率控制的角度对特定的掉话进行参数优化,为后续类似问题的分析及优化提供参考。本案例是利用CDMA网络的功率控制技术,通过提高前向业务信道的功率来优化前向链路质量,从而减少因为前向业务信道功率较小导致大量前向坏帧而引起的掉话。 相似文献
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主要研究了CDMA蜂窝通信系统的工作原理,且以基于IS-95标准的前向链路为主。利用MATLAB软件建立了前向链路中各器件的模块,实现了CDMA基带信号发生器,并在时域及频内进行了测量。 相似文献
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利用CDMA系统下行链路信号进行移动台定位的研究 总被引:2,自引:2,他引:0
深入分析了在CDMA系统中利用下行链路信号进行移动台定位存在的问题,提出使用干扰抑制的方法来抑制服务基站信号,提高定位精度的策略,详细叙述了算法流程并给出了仿真结果,结果表明,利用干扰抑制算法可以大幅度提高定位精度。 相似文献
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CDMA网络中存在前反向的多址干扰,降低了前反向容量。为了减少多址干扰对前反向容量的影响,对多址干扰产生的原因和机理进行深入分析,详细介绍了多用户检测技术和干扰消除技术。通过对造成干扰的所有用户信号信息进行检测,根据多址干扰信号的结构特征进行干扰消除和信号恢复,从而改善各个信号的信噪比,提高CDMA系统的前反向容量。重点介绍了准线性干扰消除技术QLIC(Quasi-Linear Interference Cancellation)和反向干扰消除技术RLIC(Reverse Link Interference Cancellation)的基本原理,分别对QLIC技术和RLIC技术的容量增益进行了理论推导,并计算了QLIC和RLIC对CDMA网络容量提升的程度。QLIC和RLIC是现有CDMA网络容量提升的重要技术手段,能够为运营商进行技术升级和网络部署提供重要参考。 相似文献
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Kwang Soon Kim Iickho Song Seung Chan Bang Tae-Joong Kim 《Signal Processing, IEEE Transactions on》2000,48(3):862-865
The performance of DS/CDMA systems using forward link beamforming and RAKE diversity combining is investigated analytically in frequency selective fading channels, whereas previous studies have resorted to Monte Carlo simulations in flat fading channels. The capacity of DS/CDMA systems is considerably improved by employing forward link beamforming 相似文献
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DS/CDMA communication systems are widelyused because of their obvious advantages, such as softcapacity, soft handover, higher spectral efficiency andthe ability to mitigate the effects of multi-path fading.However, the multiple access interference (MAI) andnear-far problem in DS/CDMA limit the furtherapplications of this technique. The structure of the conventional single-userdetector (CD), which neglects the presence of MAI, issimple, but its performance is limited, and the receiversuf… 相似文献
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Fuyun Ling 《Communications, IEEE Transactions on》1999,47(10):1583-1592
Coherent spread-spectrum communications with transmitted reference-based, also called pilot-based, channel estimation is considered for code-division multiple-access (CDMA) communications over fading channels. Both noncontiguous time-division multiplexed reference symbol-based and continuous code-division multiplexed channel-based schemes are described. Assuming mean square error or optimal robust channel estimation, we derive the optimal receiver structure with a maximum-likelihood convolutional decoder. In addition, the Bhattacharyya bound and the cutoff rate of the reference-assisted coherent communications are derived. These analytical results are used for evaluating system performance and for selecting parameters such as coding rate and the data to reference power ratio to optimize system performance. Simulation results are given showing that the reverse link performance in a CDMA system can be significantly improved by using the reference-assisted coherent communication instead of noncoherent reception of orthogonally coded signal 相似文献
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This paper provides an analytic method to determine how many paging channels can be simultaneously used with traffic channels
in the same CDMA forward link. So far, since one or two paging channels are enough to convey control messages from bases to
mobiles, little considerations have been given to the paging channel configuration. CDMA network operators, however, recently
plan to provide optional services which highly utilize the paging channel. Thus, more paging channels are required for the
latest situation. Since the total number of channels that can be used in the forward link is limited by the interfering cellular
environments, less traffic channels should be used if additional paging channels are required. It is the objective of this
paper to examine the capacity of forward link in terms of paging and traffic channels so as to determine the impact of introducing
value‐added services via paging channels. Different capacity regions are presented for various cellular environments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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An effect of multipath fading on the performance of a cellular code-division multiple-access (CDMA) system is analyzed in this paper. A wide-sense stationary uncorrelated scattering (WSSUS) channel model and the coherent binary phase-shift keying (BPSK) with asynchronous direct-sequence (DS) spreading signal are assumed in the analysis. The average error probability for both the forward link and reverse link of a cellular CDMA system over a frequency-selective fading channel using a conventional correlation-type receiver and RAKE receiver are derived. The impact of imperfect power control and channel capacity of a cellular CDMA system is also investigated. The closed forms of average error probability derived in the paper can save a lot of computation time to analyze the performance and channel capacity of a cellular CDMA system. The analytical results show that the performance and maximum transmission rate of cellular CDMA systems degrade with an increase in the number of simultaneous users and the number of interfering cells. The signal-to-interface ratio (SIR) for the reverse link derived in this paper can directly describe the interrelationships among a number of paths, number of users, number of interfering cells, fading factors, and maximum variation of a received unfaded signal 相似文献