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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(1):650-662
Multipath effects on code observables account for one of the major error sources in high-accuracy Global Positioning System (GPS)-based positioning, atmosphere sounding and timing applications. The multipath hemispherical model (MHM) represents one of the most widely used methods of mitigating code multipath effects by taking advantage of their spatial repeatability. The use of MHM usually assumes that the receiver code biases (RCBs) are time-invariant; however, this assumption is not always valid, as RCBs and linear combinations thereof (differential code biases, for instance) have long been found to be time-varying over a period of one day. In this contribution, we propose an extended multipath hemispherical model (EMHM) that is capable of mitigating the code multipath effects in the presence of time-varying RCBs. Consequently, the proposed EMHM has two advantages. First, the EMHM gives rise to code multipath corrections with improved reliability because it addresses the intraday variability of RCBs. Second, more interestingly, the EMHM allows easy and effective calibration of short-term temporal variations, if any, in the RCB on each frequency. These advantages are hopeful to benefit GPS code-related applications. 相似文献
133.
根据光纤陀螺光纤环受温度效应影响的机理,分析了光纤陀螺零偏产生温度误差的原因,提出了光纤陀螺基于光纤环附近多点温度的误差补偿方法,建立光纤陀螺零偏随光纤环附近多点温度及温度变化率变化的数学补偿模型。根据全温温度实验,分析光纤陀螺零偏随温度变化的规律,确定补偿模型的补偿系数,对光纤陀螺零偏进行温度误差补偿。并将多点温度补偿方法与传统的基于单点温度补偿方案的补偿效果进行对比分析。结果表明,基于两点及以上温度的温度误差补偿模型能将全温零偏稳定性降低2个数量级,全温极差降低1个数量级,优于基于单点类的温度补偿方案,且具有很高的工程应用价值。 相似文献
134.
摘要: 本文针对国防科技大学的平面感应脉冲等离子体推力器(IPPT)原型机,设计了一种基于感应涡流斥力原理的快速脉冲气体供给阀.该阀采用截锥型铍青铜簧片作为执行构件,依靠簧片开启过程中弹性变形产生的弹力提供闭合所需回复力,避免了使用额外的回复力机构,使阀整体结构得到极大简化.性能测试结果表明,该阀的动作延迟时间小于35 μs.在阀腔气体压力为100 kPa时,最大单脉冲供气量为2.5 mg.响应特性和供气量特性均满足目前IPPT原型机的需求.此外,该阀可通过调节初始充电电压和阀腔气体压力实现供气量调节.该阀可以为后续推力器原型机多工况性能试验提供有力支持. 相似文献
135.
为了评估GPS L1频点信号体制转换前后的空间信号质量,基于高增益天线接收系统采集数据,对相干自适应副载波调制(CASM)调制和QPSK调制信号质量进行对比分析。首先,简要介绍CASM调制模型,利用波形匹配技术求解L1频点授权信号伪码序列。其次,基于星座图分布和极大似然估计分别解决出QPSK和CASM调制信号分量功率分配难题。最后定量地利用相关特性参数中的S曲线过零点偏差(SCB)和相关损失(CL)对比分析L1频点信号体制转换前后各信号分量空间信号质量。该文结果可为不同信号体制下空间信号质量评估对比提供参考。 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(11):2645-2661
Timing group delay (TGD) is an important parameter that affects the positioning performance of global navigation satellite systems (GNSS). The BeiDou navigation satellite system (BDS) broadcasts TGD corrections from B3I frequency to B1I and B2I frequencies, namely TGD1 and TGD2. On July 21, 2017, BDS updated TGD values with a maximum change of more than 4 ns. In this contribution, we explain the motivation for the BDS TGD update, which is due to the systematic bias between narrowly correlated and widely correlated pseudo-ranges in BDS monitoring receivers. To investigate the impact of the updated TGD, BDS signal-in-space range error (SISRE) and user positioning performance regarding single point positioning (SPP) and precise point positioning (PPP) are analyzed. Results show that after the update of TGD, the difference between the new TGD and multi-GNSS experiment (MGEX) differential code bias (DCB) decreases from 1.38 ns to 0.29 ns on TGD1 and from 0.40 ns to 0.25 ns on TGD2. With the contribution of more accurate TGD, the systematic bias of BDS radial SISRE no longer exists, and the overall BDS SISRE also reduces from 1.33 m to 0.87 m on B1I/B2I frequency, from 1.05 m to 0.89 m on B1I frequency, from 0.92 m to 0.91 m on B2I frequency, respectively, which proves the similar precision of BDS TGD and MGEX DCB. One week of statistical results from 28 globally distributed MGEX stations shows that the SPP performance improves on non-B3I frequencies after the TGD update, with a maximum improvement of more than 22% for the B1I/B2I or B1I/B3I combination. The new TGD mainly reduces SPP positioning bias in the East component. The updated TGD also slightly improves the PPP convergence performance for the B1I/B3I combination, but mostly contributes to a more accurate estimation of the receiver clock and ambiguities. 相似文献
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针对传统金属探测方法的缺点,提出数字电感探测法。基于电涡流原理,采用先进的数字电感转换器LDC1000做为传感器,通过前端自制印制板电感线圈检测金属,通过计算将测量结果转换为数字量,经串行外设接口(以下简称SPI)与高性能ARM处理器Cortex-M4相连,可实现高速、高精度金属测量。实测结果表明:本传感器克服了传统电感测量方法抗干扰能力差、模拟接口、精度低的缺点,实现了数据采集的高速、可靠,并使测量精度提高到亚微米级,可实现对金属物距离、角度、运动、位移、压缩等的高精度测量。 相似文献