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本文提出了一种基于分数阶傅里叶变换(Fractional Fourier Transform,FRFT)的多线性调频(Linear Frequency Modulation,LFM)信号二维波达方向(Direction of Arrival,DOA)估计方法.该方法利用FRFT对LFM信号的能量聚集特性,构造出一种新的分数阶傅里叶域的阵列信号数据模型,并利用MUSIC算法实现对多个LFM信号的二维DOA估计.仿真实验验证了算法的有效性. 相似文献
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针对分布式MIMO OFDM系统,提出一种基于分数阶傅里叶变换(FRFT)的定时同步与频偏捕获算法。发送端采用线性调频信号作为训练序列,接收端通过分数阶傅里叶变换,先对各个发送天线之间的相互干扰进行抑制,再完成定时同步与频偏捕获。相比于已有算法,该算法有效地提升了定时同步与频偏捕获的精度。仿真结果表明了其有效性。 相似文献
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针对均匀圆阵(UCA),根据不同线性调频(LFM)信号在对应阶次上的分数阶傅里叶变换(FRFT)域具有能量聚集性的特点,将不同时频特性LFM信号在FRFT域分离成一系列平稳单频信号,构造出FRFT域上新的空时频分布模型数据,结合MUSIC算法,提出了一种新的均匀圆阵多宽带LFM信号的二维DOA估计。通过仿真实验验证了该方法的有效性。 相似文献
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针对多项式相位信号波达方向(DOA)估计研究较少的问题,提出了一种基于分数阶傅里
叶变换(FRFT)的多项式相位信号(PPS)的DOA估计算法。该算法首先通过多项式相位变换,估
计出PPS的最高阶相位系数,从而可以消除最高阶项。运用这一降阶思想,依次消除高阶项
,这样PPS可降为线性调频(LFM)信号,然后将宽带的LFM信号转化为分数阶Fourier域窄带的
平稳信号。在相应的分数阶Fourier域,运用求根MUSIC算法对信号进行DOA估计,从而把LFM
信号的DOA估计推广到了PPS的DOA估计。理论分析和仿真实验表明,该方法能很好地估计出P
PS的DOA,并且简洁。 相似文献
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该文提出一种双基地MIMO雷达线性调频(LFM)信号参数的联合估计新方法。在所提出的新的双基地MIMO雷达的信号模型基础上,利用分数阶傅里叶变换对线性调频(LFM)信号的能量聚集特性进行提取,根据分数阶傅里叶变换域内的峰值点对多普勒频移尺度和时延进行估计,并采用FRFT-MUSIC算法实现了线性调频(LFM)信号收发角的联合估计,实现了收发角的自动配对。仿真实验验证了算法的有效性。 相似文献
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《信息技术》2017,(6):124-128
雷达回波中往往存在严重的干扰,采用线性调频信号(linear frequency modulation,LFM)的脉冲压缩雷达系统中,直接对回波信号进行脉冲压缩往往得不到好的效果。文中利用线性调频信号在分数阶傅里叶变换(fractional fourier transform,FRFT)中的强能量聚集性的特点,在分数阶傅里叶域对混合回波进行自适应滤波,再将滤波后的信号变换回时域进行脉冲压缩处理。自适应滤波算法采用一种改进的变步长NLMS算法,相对于传统固定步长NLMS算法有较好的滤波结果。仿真结果表明,经过分数阶傅里叶域自适应滤波后的信号在脉冲压缩后的目标检测结果有了很大的改善,明显提高了脉冲压缩雷达的检测性能。 相似文献
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基于Agent的智能决策支持系统 总被引:2,自引:0,他引:2
针对传统DSS的不足,把专家系统和范例推理技术以及数据仓库、数据挖掘技术运用于DSS中,把传统的DSS改进为IDSS,鉴于agent技术构件重用等特点,把agent技术运用到IDSS中,提出了一个实现基于agent技术的IDSS框架,最后探讨了系统实现的主要技术。 相似文献
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超宽带脉冲信号的光学生成方法研究 总被引:1,自引:0,他引:1
近年来超宽带(UWB)通信技术迅猛发展,在测量、雷达技术、民用和军事无线通信中有着重要的应用,UWB-over-fiber技术已经成为目前研究的热点,其中就包括UWB脉冲信号的产生方法。区别于传统的电子学方法,光子学产生方法不受电子瓶颈制约,可以实现很高的带宽,并且具有抗电磁干扰、重量轻、结构紧凑的优点。通过对比国内外本领域研究成果,讨论及总结了以下三种原理的UWB脉冲信号的光学生成方法:1)相位调制-强度调制转换(PM-IM);2)半导体光放大器(SOA)的非线性效应;3)频谱塑形和色散所致频域-时域映射,然后对各种方案进行了对比分析。 相似文献
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Wei Liu Ming-Fu Li Soo-Jin Chua Nakao Akutsu Koh Matsumoto 《Journal of Electronic Materials》1999,28(4):360-363
Semi-transparent Au-Schottky contacts on n-GaN were fabricated and studied by room-temperature photoreflectance spectroscopy.
A significant difference was observed in the photoreflectance spectra before and after the evaporation of Au-Schottky contacts.
This can be interpreted due to the formation of Schottky barrier at the interface between Au and GaN. Furthermore, for the
higher doping sample, Franz-Keldysh oscillations were observed in the photoreflectance, which allowed the accurate determination
of Au-Schottky barrier height on GaN. 相似文献
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This paper presents a new Transmitted Reference (TR) Ultra-WideBand (UWB) receiver based on Spatial Diversity (SD), which employs Multi-Antenna Technology (MAT) to improve the performance of TR-UWB receiver. According to the amplitude of correlator output of every antenna branch, this paper analyzed the performances of the proposed TR-UWB receiver employing three different kinds of combina-tion strategies, i.e., Maximum Ratio Combination (MRC), Equal Gain Combination (EGC), and Selective Combination (SC), which are different from conventional ones, and theoretically proved that the performance of EGC is better than MRC. Simulation results verify that when EGC is adopted and BER=10–3, increasing three antennas provides Signal to Noise Ratio (SNR) gain of about 3 dB in CM4 channel and SNR gain of about 2 dB in CM2 channel. 相似文献
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Germanium (Ge) pin photodiodes show clear direct band gap emission at room temperature,as grown on bulk silicon in both photoluminescence (PL) and electroluminescence (EL).PL stems from the top contact... 相似文献
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光子辅助的毫米波通信因其超带宽优势在下一代宽带无线接入网中有着广泛的应用前景,本文基于单个激光源和一个双极化马赫-曾德尔调制器(dual-polarization Mach-Zehnder modulator,DP-MZM)的光路结构产生了频率稳定的偏振复用毫米波信号,联合VPI与MATLAB仿真环境对单边带(single sideband,SSB)偏振复用四相相移键控(polarization-division-multiplexing,PDM)quadrature phase shift keying,QPSK、16阶正交幅度调制(16-ary quadrature amplitude modulation,16QAM)和32阶正交幅度调制(32-ary quadrature amplitude modulation,32QAM)信号分别实现了70 km、65 km与50 km的有效传输,并结合概率整形(probability shaping,PS)技术在28 GHz波段上,以相同净比特传输速率对比分析了均匀16QAM与PS-16QAM,均匀32QAM与PS-32QAM的SSB矢量毫米波(millimeter wave,MMW)信号在光纤传输条件下的误码率(bit error rate,BER)性能。仿真结果表明:在相同净比特速率,以硬判决阈值3.8×10^(-3)为判断条件,在普通单模光纤(single-mode fiber,SMF)传输系统中,PS-16QAM/32QAM信号光功率约有0.3 dBm的提升,非线性光纤(nonlinear fiber NLF)传输系统中,PS-16QAM信号光功率约有0.8 dBm的提升,PS-32QAM信号光功率约有0.5 dBm的提升,结果表明:经过PS后的MMW信号光纤传输性能有明显改善。 相似文献
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KANG Xiao-fei YANG Jia-wei MEN Shuo .State Key Laboratory of Integrated Service Networks Xidian University Xi'an China .College of Electronic Information Automation Chongqing University of Technology Chongqing China 《中国邮电高校学报(英文版)》2011,18(6):38-43
A novel receiver is proposed in this paper that uses the blind adaptive multi-user detection(MUD) technique to deal with the presence of multiple-access interference(MAI) and inter-symbol interference(ISI) in terms of high speed time-hopping ultra-wideband(TH-UWB) system.The receiver firstly adopts constrained recursive least squares constant modulus algorithm(RLS-CMA) to conduct adaptive decorrelation for eliminating MAI and ISI,and then uses projection approximation subspace tracking with deflation(PASTd)... 相似文献
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C. Fulk R. Sporken J. Dumont D. Zavitz M. Trenary B. Gupta G. Brill J. Dinan S. Sivananthan 《Journal of Electronic Materials》2005,34(6):846-850
We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron
spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations.
It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311)
had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy,
while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge
site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging
atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites.
This would ensure a nonpolar, B-face growth. 相似文献