共查询到17条相似文献,搜索用时 140 毫秒
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概述了二元相移键控(BPSK)调制以及二进制偏移载波(Binary Offset Carrier,BOC)的调制原理,并基于由中国科学院主导研发的中国区域定位系统(Chinese Area Positioning System,CAPS)的实际情况,对其调制信号的测距精度、跟踪性能、多径误差的影响做了分析。分析结果对于中国区域定位系统信号体制设计、调制方式的选取具有一定的借鉴意义。 相似文献
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分析了射频前端带宽与BOC信号自相关函数的关系,研究了射频前端带宽和早迟码间距对S曲线的影响。在规范的TOA误差估计模型框架下,采用非相干延时码跟踪锁定环,推导出非相干延时锁定环理论计算的码跟踪误差与射频前端带宽、早迟码间距、载噪比、积分时间和码环路带宽之间的关系表达式,从而定量地分析了非相干延时锁定环的码跟踪误差。最后对BPSK-R信号和BOC(10,5)信号的码跟踪性能做了比较,比较表明,BOC(10,5)信号的码跟踪性能优于传统的BPSK-R信号,在相同的码跟踪精度条件下,BOC(10,5)比10.23 MHz BPSK-R信号所需要的载噪比约低7 dB,比1.023 MHz BPSK-R信号低15 dB左右。 相似文献
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在许多场合 ,需要找出BPSK(BinaryPhaseShiftKey ,即二进制相移键控 )调制信号的调制时刻。但实际上并不能直接发现BPSK调制信号的调制时刻 ,只能看到有明显的幅度调制现象。对这种现象产生的原因和用途作了分析 ,并通过仿真实验对这种现象进行了验证。 相似文献
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闭合相位法是实现长基线恒星光干涉高分辨成像的重要技术手段之一,获得精确的闭合相位信息是进行光干涉图像重构的先决条件.提出一种基于精密光程差调制的时域干涉信号闭合相位检测方法,在3路干涉臂上进行非冗余精密光程调制,并通过多次干涉测量结合数据拟合的方法消除光程差调制中存在的正弦误差,使得光程调制的精度达到20 nm以内.引入高速探测器件提升时域干涉信号的采样频率,对探测器上获得的时域干涉信号进行傅立叶变换处理,获得3路干涉臂精确的闭合相位信息.室内实验结果表明,基于精密光程调制的时域信号闭合相位计算精度可以达到1/50波长以内. 相似文献
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一个标准时间信息码由广播电台传送,是有许多优点:复盖面积比较大,不要建立专门的标准时间发播台,使用低价接收机和简单解码器,可以获得较高时间同步和校频精度。文中介绍了目前广播电台报时信号形式。编码时间信号采用“PSK”调制形式,主要目的满足不同用户的需要。解码器采用匹配滤波器,以便获得最佳接收。 相似文献
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V. K. Mishra Meera Gupta B. N. Mishra S. K. Nigam A. P. Mishra 《Journal of Astrophysics and Astronomy》2008,29(1-2):257-262
The long-term modulation of cosmic ray intensity (CRI) by different solar activity (SA) parameters and an inverse correlation between individual SA parameter and CRI is well known. Earlier, it has been suggested that the concept of multi-parametric modulation of CRI may play an important role in the study of long-term modulation of CRI. In the present study, we have tried to investigate the combined effect of a set of two SA parameters in the long-term modulation of CRI. For this purpose, we have used a new statistical technique called “Running multiple correlation method”, based on the “Running cross correlation method”. The running multiple correlation functions among different sets of two SA parameters (e.g., sunspot numbers and solar flux, sunspot numbers and coronal index, sunspot numbers and grouped solar flares, etc.) and CRI have been correlated separately. It is found that the strength of multiple correlation (among two SA parameters and CRI) and cross correlation (between individual SA parameter and CRI) is almost similar throughout the period of investigation (1955–2005). It is also found that the multiple correlations among various SA parameters and CRI is stronger during ascending and descending phases of the solar cycles and it becomes weaker during maxima and minima of the solar cycles, which is in accordance with the linear relationship between SA parameters and CRI. The values of multiple correlation functions among different sets of SA parameters and CRI fall well within the 95% confidence interval. In the view of odd-even hypothesis of solar cycles, the strange behaviour of present cycle 23 (odd cycle), as this is characterized by many peculiarities with double peaks and many quiet periods (Gnevyshev gaps) interrupted the solar activity (for example April 2001, October–November 2003 and January 2005), leads us to speculate that the solar cycle 24 (even cycle) might be of exceptional nature. 相似文献
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本文介绍一种称作三位调制的望远镜副镜调制新方法。在用望远镜作L和M波段的红外天文观测时,采用这种新调制方法,在一定条件下可以替代望远镜所做的双束转换运动而获得令人满意的结果。对于控制功能不是很强的望远镜,或者进行一些不允许望远镜摆动的特殊观测(如红外偏振测量),这种方法极为有用。本文介绍了这种新调制方法原理和电路,并且使用1.2米红外望远镜比较了用这种新调制方法和用通常的副镜二位调制方法对一组红外标准星的测量结果:在J和K波段;两种方法的结果大体相同,在L波段,新调制方法显示出明显的优越性。 相似文献
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We study the modulation of galactic cosmic rays (GCR) due to high-speed streams (HSS) identified in the solar wind. We compare the GCR modulation due to i) streams with different speed, ii) streams of different duration, and iii) streams from different solar sources. We apply the method of superposed-epoch analysis to analyze the interplanetary plasma and field parameters during the passage of streams with distinct plasma and field characteristics. We use the plasma/field characteristics to distinguish various features of solar sources and interplanetary structures, and discuss the observed differences in the cosmic-ray response. We study the influence of speed, duration, and solar sources of the streams on the GCR modulation. We discuss the relative importance of different solar-wind parameters in the modulation process. 相似文献
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Marius S. Potgieter 《Astrophysics and Space Science》1995,230(1-2):393-403
The modulation of cosmic rays (CRs) in the heliosphere is a dynamic and therefore a highly time-dependent process. Numerical models with only a time-dependent neutral sheet prove to be successful when moderate to low solar activity occurs but fail to describe large and discrete steps in modulated CRs when solar activity is high. To explain this feature of heliospheric modulation, the concept of global merged interaction regions (GMIRs) is required. The combination of gradient, curvature and neutral sheet drifts with these GMIRs has so far been the most successful approach in explaining the 11-year and 22-year cycles in the long-term modulation of CRs. 相似文献
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The measured modulation of cosmic rays deposited in the stratosphere over a sunspot cycle produces an oscillating source of stratospheric NO with an 11-yr (quasi) period. The resulting modulation of ozone over this period is calculated and is shown to give good agreement with available measurements of the time lag, the latitude dependence and the magnitude of cyclic variations of ozone. This correlated modulation is then used to discuss the effect on ozone of the injection of NO into the stratosphere from artificial sources, viz. a fleet of supersonic transports and nuclear bomb explosions in the atmosphere. 相似文献