共查询到19条相似文献,搜索用时 156 毫秒
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为了能够在低信噪比下实现微弱信号的快速捕获,必须增加处理增益.要提高增益就要进行累积,而累积易受导航电文翻转和多普勒频偏的影响.为了克服两者的影响,传统的捕获方法通常采用相干加非相干累加的捕获算法,但是非相干累加又引入了平方损耗,并且对频率走动效应补偿有限.随着积分时间长度的加长,数据翻转和多普勒变化的影响会愈加突出,传统的算法已不能满足要求.对此,一种新的弱信号快速捕获算法被提出.该算法采用奇偶相间分别相干累加的方法进行数据补偿和并行多普勒搜索的方法进行多普勒补偿,从而在尽量延长单次相干积分时间的基础上,实现了多次相干积分结果的多次相干累加.最后计算机仿真验证,该方法是有效的和正确的,并且与传统方法相比,同样条件下,改进算法的累加次数是传统算法的1/8,捕获时间缩短了1/4以上. 相似文献
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为了提高伪码捕获性能,在分析常用相干-非相干码捕获平方损耗及捕获性能的基
础上,提出了一种改进的两级相干累加伪码捕获算法。通过在第二级累加之前对多普勒频偏
进行有效补偿,实现了相干累加,提高了捕获性能;采用FFT实现,解决了工程实现的难
度。与传统的相干-非相干累加码捕获算法相比,该方法具有捕获门限低、多普勒频偏可估
计等优点。计算机仿真表明,该方法仅比理论值恶化1 dB,具有高效的捕获性能。
同时,分析表明该方法实现简单、快捷,具有很好的工程应用前景。 相似文献
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在现阶段,"北斗"B1I信号在D1导航电文中引入现代化GPS和Galileo系统常用的二次编码调制,使得比特跳变周期变短,降低了系统的捕获灵敏度.为解决上述问题,提出了一种基于码元排布顺序的改进相干累积捕获算法,通过分组来遍历并统计一个数据段的累加和相关值,并且采用一种改进的判决方法进行双重判决,最终确定其中最大相关值并完成捕获.此方法有效延长了积分长度,克服了因Neumann-Hoffman(NH)码造成的相干累积时间过短的缺陷,能改善在低信噪比环境下的信号捕获能力.在高斯白噪声模型下对各个捕获算法进行的仿真对比结果表明,所提算法在低信噪比(-36~-34 dB)情况下,与补零算法相比,信号捕获灵敏度有约1.7 dB的提升. 相似文献
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为实现两个射频识别(RFID)碰撞标签信息的检测和分离,提出一种利用Gen2标准中FM0标签编码固有记忆特性的检测方法。通过对FM0比特编码特点和碰撞标签信息的无记忆检测分析,得到基于单个比特持续时间的无记忆检测方法的条件错误概率和单个标签信息检测的误码率;然后利用单个FM0比特编码需要前一比特的“记忆”特性,得到对应于前一比特的一对测量值和对应于下一比特的一对测量值,进而得到碰撞标签信息的1比特记忆辅助检测时的条件错误概率和误码率性能;并对在帧Aloha媒质接入方案中采用提出的检测方法时的N个标签群的总延迟减少性能进行了分析。仿真实验结果表明,提出的1比特记忆辅助检测方法,相比于无记忆检测具有更好的误码率性能,且能减少标签群接入时的总延迟。 相似文献
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《Solid-State Circuits, IEEE Journal of》1980,15(2):184-189
A 64 Kbit dynamic RAM is described. The RAM features a novel memory cell using a polysilicon-dielectric-polysilicon (PDP) capacitor. This structure provides performance and density advantages over the conventional approaches. A new sense amplifier configuration is also described in detail. It multiplexes two pairs of bit lines for each sense amplifier. Thus the number of memory cells per bit line is halved. This reduces the length of each bit line, thereby increasing the signal voltage available to the sense amplifier. A compatible dummy cell design is included in the discussion. Using conservative processing (3.5 /spl mu/m device channel length with 700 /spl Aring/ gate oxide thickness) a die size of 3.2 mm/spl times/7.9 mm is achieved. Experimental data are presented in the text. 相似文献
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针对弱信号条件下GPS C/A码捕获问题,提出一种基于平均相关和差分相干累积的码捕获算法。首先,引入相干能量最大值与第二大值的比值作为判决变量,仿真了各种捕获算法的虚警概率得到最佳的判决门限;然后,通过设置的判决门限获得不同多普勒频率偏差及信噪比条件下的检测概率;最后,比较了所提差分相干累积算法、相干非相干累积算法以及非相干累积算法的捕获灵敏度。仿真实验表明,在相同接收数据长度的情况下,采用差分相干累积算法比其他2种算法提高捕获灵敏度约2 dB。 相似文献
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《Solid-State Circuits, IEEE Journal of》1980,15(1):33-38
A special purpose microprocessor for real time processing of analog signals is described. Design and implementation of architecture allowing a user programmable and erasable read only memory (EPROM), a 25 bit digital processor and a 9 bit analog acquisition system on the same substrate is discussed. The relationship between the device's resources and specific signal processing building blocks is discussed. 相似文献
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Kurosawa I. Nakagawa H. Aoyagi M. Kosaka S. Takada S. 《Solid-State Circuits, IEEE Journal of》1991,26(4):572-577
The first fully operational Josephson RAM in LSI level integration is described. The chip is designed as a 4 b× 256-word data RAM unit for a 4 b Josephson computer. A variable-threshold memory cell and the related memory architecture are used. They are so simple in structure that the fabrication can be accomplished using current Josephson junction technology. A directly coupled driver gate for a resistive bit line applies an accurate and stable driving current to the memory cell array. The RAM chip is fabricated with a 3 μm Nb/Al-oxide/Nb junction technology. For obtaining reliable RAM chips, a plasma-enhanced CVD (chemical-vapor-deposited) silicon dioxide layer is introduced for insulation between the ground plane and the base electrode. The thermal uniformity of the wafer is improved during the oxidation process for making a tunnel barrier. Installing this RAM chip together with a Josephson processor permitted the functions of a computer, including a memory access, to be successfully demonstrated. The access time was found to be 500-520 ps by measuring a test chip 相似文献
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Nii K. Maeno H. Osawa T. Iwade S. Kayano S. Shibata H. 《Solid-State Circuits, IEEE Journal of》1995,30(3):316-320
A novel memory cell circuit for multiport RAM on CMOS Sea-of-Gates (SOG) has been proposed. It contributes to the operation both at high speed and at low voltage. In addition, a fourfold read bit line technique is also proposed to reduce the access time. A multiport RAM generator with the novel memory cell has been developed. 2-port or 3-port RAM's with flexible bit-word configurations are available. Test chips containing seven generated RAM's were designed and fabricated on 0.5 μm CMOS SOG. The experimental results of the chip show that each RAM operates at over 1.4 V and that the address access time of the 3-port RAM (16b×256w) is 4.8 ns at 3.3 V 相似文献
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空间太阳望远镜图像积分中1 bit相关器的研究 总被引:2,自引:0,他引:2
空间太阳望远镜(SST)系统采用图像积分方法提高太阳矢量磁图的信噪比(SNR).在图像积分过程中,基于图像强度信息的相关器难以满足航天应用中系统实时性和低资源消耗要求,为此提出使用1 bit相关器实现图像快速相关运算.1 bit相关算法以异或逻辑运算代替常规算法中的乘法,提高了运算速度,同时减小硬件实现复杂度.针对太阳米粒图像,给出1 bit相关算法方案,并研制出基于FPGA DSP架构的相关器.测试结果表明,该相关器的算法精度、相关运算时间均能满足SST需求,而FPGA资源消耗仅为基于快速傅里叶变换(FFT)相关器(8 bit数据)的1/10. 相似文献