共查询到20条相似文献,搜索用时 78 毫秒
1.
2.
3.
4.
5.
在对基于多相滤波结构的宽带数字信道化接收机理论分析的基础上,结合九阵元空间谱估计系统的实际要求,对宽带信道化接收机的处理算法与实现进行了研究,深入分析其具体化的处理结构,将处理中的多路并行结构转化为串行处理.针对多相滤波处理中具体的数据流结构,推导出FPGA实现的优化实现结构.给出了前述优化结构的详细推导和具体实现,最后在EP2S60 FPGA芯片上实现了包括数字下变频和多相滤波信道化处理的接收机系统,验证了优化结构的可实现性和有效性. 相似文献
6.
一种高效的宽带数字信道化接收方法 总被引:2,自引:1,他引:2
宽带雷达对抗侦察数字接收机具有较宽的瞬时频率覆盖特性和较高的截获概率,并能处理同时到达的多个信号。多相滤波信道化接收机是实现宽带接收的一种方法,其抽取运算在滤波运算之前,运算量小,输出速率低,便于后续处理,是一种高效结构。给出了多相滤波信道化数字接收机的基本原理和实现方法,采用重叠一半多相滤波信道化数字接收机能够有效消除接收盲区,实现全概率接收并消除虚假输出,通过仿真试验证明了其有效性。 相似文献
7.
8.
9.
10.
11.
The interfacial microstructure and shear strength of Sn3.8Ag0.7Cu-xNi (SAC-xNi, x = 0.5, 1, and 2) composite solders on Ni/Au finished Cu pads were investigated in detail after aging at 150 °C for up to 1000 h. The interfacial characteristics of composite solder joints were affected significantly by the weight percentages of added Ni micro-particles and aging time. After aging for 200 h, the solder joints of SAC, SAC-0.5Ni and -1Ni presented duplex intermetallic compound (IMC) layers regardless of the initial interfacial structure on as-reflowed joints, whose upper and lower IMC layers were comprised of (CuNi)6Sn5 and (NiCu)3Sn4, respectively. Only a single (NiCu)3Sn4 IMC layer was ever observed at the SAC-2Ni/Ni interface on whole aging process. Based on the compositional analysis, the amount of Ni within the IMC regions increased as the proportion of Ni addition increased. The IMC (NiCu)3Sn4 layer thickness on the interface of SAC and SAC-0.5Ni grew more slowly when compared to that of SAC-1Ni and -2Ni, while for the (CuNi)6Sn5 layer the reverse is true. Except the IMCs sizes are increased with increased aging time, the interfacial IMCs tended to transfer their morphologies to polyhedra. In all composite joints testing, the shear strengths were approximately equal to non-composite joints. The fracturing observed during shear testing of composite joints occurred in the bulk solder, indicating that the SAC-xNi/Ni solder joints had a desirable joint reliability. 相似文献
12.
自行设计了基于8-羟基喹啉铒(ErQ)为发射层(EMLs)和二硝酰胺铵(ADN)为蓝光主体材料的近红外有机发光二级管.器件的基本结构为(p-Si/NPB/EML/Bphen/Bphen:Cs2CO3/Sm/Au),设计并比较了三套不同发射层结构(ErQ/ADN为双层结构器件,(ErQ/ADN)×3为多层结构器件,ErQ:ADN为掺杂结构器件)的器件.三组器件在一定的偏压下,均可发出1.54μm的光,对应三价铒离子4I13/2→4I15/2的跃迁.其中,ADN:ErQ(1∶1)掺杂结构的近红外电致发光强度是ADN/ErQ双层结构中的三倍.此外,不同掺杂浓度的ADN:ErQ复合膜做了以下表征:吸收谱、光致发光谱和荧光寿命谱.实验结果证实了在近红外电致发光过程中存在从ADN主体分子到ErQ发射分子的高效率的能量转移. 相似文献
13.
设计了(Bi0.55Na0.5)1-X(BaaSrb)xTiO3(BNBST[100x-100a/100b])无铅压电陶瓷新体系。该体系压电陶瓷具有工艺特性及压电响应好,压电常数高的特点,且有实际应用前景的新型压电陶瓷材料体系。采用传统的陶瓷工艺制备了(Bi0.55Na0.5)1-X(BaaSrb)xTiO3无铅压电陶瓷,研究了制备工艺参数对其物化结构性能的影响。生料的热重-差热(TGA-DTA)分析表明,粉料合成过程中,先是SrTiO3、BaTiO3的形成,然后是(Bi0.5Na0.5)Tio,的形成,同时三者形成固溶体;密度测试表明,陶瓷的体积密度随烧结温度的升高而增大,可较易获得理论密度94%的陶瓷;X-射线能谱分析(EDAX)研究表明,陶瓷的Bi、Na的挥发随着烧结温度的升高而加剧。研究结果表明,要制备性能优良的无铅压电陶瓷,需要精确控制制备工艺。 相似文献
14.
Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years. 相似文献
15.
利用分子结构的螺旋对称性,建立了一个包括钠离子的三链DNA分子poly(dT)*poly(dA)*poly(dT)的晶格动力学模型,计算了poly(dT)*poly(dA)*poly(dT)的氢键呼吸模式.结果发现钠离子的加入明显地淬灭了位于较低频率的几个最为强烈的Hoogensteen氢键呼吸模式,而对Watson-Crick氢键呼吸模式影响不明显,这说明钠离子能提高poly(dT)*poly(dA)*poly(dT)三螺旋结构的稳定性.该计算结果很好地解释了poly(dT)*poly(dA)*poly(dT)的热融化实验. 相似文献
16.
聚对苯撑苯并双(口恶)唑发光及其器件制备 总被引:2,自引:0,他引:2
采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加. 相似文献
17.
本文对免疫酶组织化学的样品制备程序和染色方法做了详细的阐述。用直接法、间接法和ABC法,对人小肠免疫酶的定位,进行了光镜和电镜的观察,染色阳性反应显著,获得了满意的效果。并对染色技巧做了分析和探讨。 相似文献
18.
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
19.
Fangqiu Wang Chenghua Wang Shengkui Zhou 《International Journal of Electronics》2013,100(10):1765-1788
Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm. 相似文献
20.
在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65~4GHz的频带内隔离深度可达-40~75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证. 相似文献