排序方式: 共有84条查询结果,搜索用时 31 毫秒
71.
针对GPS M码信号的特点和在抗干扰方面的优越性,为实现对其有效干扰,以接收机相关滤波输出功率谱变化情况作为定性评估依据,以码跟踪误差和星历误码率作为定量评估指标,对单频、带限高斯噪声和同速率伪码3种典型压制干扰样式的干扰效能进行分析。通过建立M码信号的接收系统模型,从理论上推导了干扰对各具体评估要素的影响过程以及各要素之间的统一性。仿真结果表明,单频干扰效果最好,消除副载波调制影响的同速率伪码干扰次之,带限高斯噪声干扰效果较差。考虑到单频干扰对干扰频偏设置的较高要求以及容易被接收机通过频域滤波而抑制掉的实际情况,结合实施灵巧干扰的难易程度,可选择同速率伪码干扰作为对M码信号的压制干扰样式。 相似文献
72.
73.
74.
时分数据调制(TDDM)作为一种新的调制方式受到广泛关注,文中以BOC信号的TDDM调制为例,研究了该调制方式的产生机理及特性.利用其与BOC信号频谱特性的相似性,进而通过研究现有BOC信号捕获算法及其优缺点,结合TDDM扩频方式的特殊性,设计了基于TDDM调制方式的同步捕获算法.对该捕获算法进行建模,并在不同的信噪比条件下,利用MATLAB7.1完成对捕获算法的同步仿真,验证了该直捕算法的可行性和有效性. 相似文献
75.
随着卫星导航信号的发展,对如何正确实现信号同步接收的时效性、复杂度等提出了挑战。为此,在研究新特性信号的基础上,重点开展其精同步技术研究,针对BOC调制信号特性,从效率及速度角度展开精同步方法研究,并对其进行仿真及分析。结果表明,此方法可以快速、有效地达到精同步的目的,并正确解调出导航电文数据. 相似文献
76.
77.
A cardanol/m‐cresol‐based copolymer was esterified using di‐tert‐butyl dicarbonate (t‐BOC), which makes it a suitable candidate as a possible e‐beam resists. This work reports a full characterization of the product using the techniques of FTIR and UV–Visible spectroscopy, one dimensional 1H NMR, 13C NMR, DEPT‐135. Two dimensional NMR experiments such as, COSY, HSQC, and HMBC have been employed for exhaustive probing of the microstructural details of this derivatized copolymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
78.
Using soil biomass as an indicator for the biological removal of effluent-derived organic carbon during soil infiltration 总被引:12,自引:0,他引:12
This study investigates the relationship between soil biomass and organic carbon removal during the infiltration of conventionally treated effluents used for groundwater recharge during soil-aquifer treatment (SAT). Investigations were conducted on samples collected from full-scale SAT sites, revealing a positive correlation between biodegradable organic carbon (BOC) concentrations in the recharged effluents and total viable soil biomass concentrations in the infiltration zone of soil samples collected from respective recharge basins. Findings of this study suggest that BOC limits soil biomass growth and was able to support a steady-state concentration of viable soil biomass that is characteristic to BOC concentrations introduced with the recharged effluents. All investigated sites indicate that BOC is primarily removed within 30 cm soil depth leading to a significant increase in soil biomass levels (measured as substrate induced respiration (SIR), total viable biomass, and dehydrogenase activity (DHA)). Controlled biological column studies revealed that the primary components of BOC in domestic effluents are organic colloids. Findings of this study support that hydrophobic acids, commonly believed to be recalcitrant, may also be attenuated by biological processes during soil infiltration. 相似文献
79.
针对卫星导航接收机容易受多径信号干扰的影响,提出了一种基于最大似然估计的加权ELS(超前/滞后斜率)技术BOC多径减弱方法。该方法先经过最大似然估计得到直射信号估计值,再检测多个BOC信号自相关函数峰两边的斜率,可以有效地减小多径信号对环路的影响,性能优于传统的窄相关技术和ELS技术,并且只增加较少的计算复杂度。通过对BOC(10,5)的多径误差包络仿真分析表明:该方法能有效减小多径干扰引起的跟踪误差。 相似文献
80.
该文基于常规二进制偏移载波(BOC)调制体制的数学模型,提出一种新型的基于扫频二进制偏移载波调制(FC-BOC)的伪码扩频体制。在这种调制体制中,BOC调制体制数学模型中的固定频率二进制偏移载波被改进为线性扫频二进制偏移载波,使之不仅继承了BOC信号的性质,还具有更加独特的性质。仿真研究和算法实验表明:FC-BOC调制体制保留了BOC调制体制的主要优点,特别是具有狭窄的主相关峰和出色的副峰抑制特征而避免了多相关峰模糊性,功率谱密度函数呈现类似带通白噪声功率谱密度函数的形态。FC-BOC调制体制信号生成算法、接收算法的结构与常规BOC调制体制类似,算法复杂度相当于常规BOC调制体制,适合纯数字编程设计实现。 相似文献