At 19:45 Beijing time on November 5,a LM-3B/Yuanzheng 1 launch vehicle lifted off from the Xichang Satellite Launch Center,putting the first two Bei Dou 3 satellites into orbit after the separation of the rocket upper...At 19:45 Beijing time on November 5,a LM-3B/Yuanzheng 1 launch vehicle lifted off from the Xichang Satellite Launch Center,putting the first two Bei Dou 3 satellites into orbit after the separation of the rocket upper stage and the satellites.The launch opens up a new era for the global networking of the Bei Dou Navigation Satellite system(Bei Dou system),which is the final step of the"three-step development strategy"of the system.展开更多
The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the g...The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.展开更多
为了解决生鲜农产品供应链信息传递不连续、不完整、不真实等问题,防止农产品给人民生活健康带来威胁,该研究开发了基于近场通信技术的数据采集终端。该文分析了生鲜农产品供应链数据采集设备及工作环境的特点,开发一种基于近场通信技术...为了解决生鲜农产品供应链信息传递不连续、不完整、不真实等问题,防止农产品给人民生活健康带来威胁,该研究开发了基于近场通信技术的数据采集终端。该文分析了生鲜农产品供应链数据采集设备及工作环境的特点,开发一种基于近场通信技术（near field communication）、北斗系统（bei dou system）及全球移动通信系统（global system for mobile communications）集成技术的生鲜农产品供应链数据采集终端。该终端包含4个模块：NFC模块、系统CPU模块、北斗模块和GSM模块及电路系统。终端在写入数据时,同时将北斗加密数据通过NFC芯片PN532写入NFC标签,并通过GSM模块以短信的方式传递给后台数据库,利用RS232将数据信息传入节点企业平台,实现生鲜农产品数据信息的三重备份。该采集终端借助物联网及无线传感网的技术优势,实现生鲜农产品供应链各环节数据的自动智能采集并进行加密,满足企业在生产过程中不断变化环境下的数据采集及存储需求,该终端在极端环境下读取速度虽然降低了10%~25%,但存储率依然为100%,满足生鲜农产品供应链数据采集的需要,能够实现节点企业间信息连续度,为实现生鲜农产品可追溯提供参考。展开更多
文摘At 19:45 Beijing time on November 5,a LM-3B/Yuanzheng 1 launch vehicle lifted off from the Xichang Satellite Launch Center,putting the first two Bei Dou 3 satellites into orbit after the separation of the rocket upper stage and the satellites.The launch opens up a new era for the global networking of the Bei Dou Navigation Satellite system(Bei Dou system),which is the final step of the"three-step development strategy"of the system.
基金supported by National Key R&D Program of China (Grant Nos. 2016YFB0501700, 2016YFB0501701)National Natural Science Foundation of China (Grant No. 41374019)
文摘The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.
文摘为了解决生鲜农产品供应链信息传递不连续、不完整、不真实等问题,防止农产品给人民生活健康带来威胁,该研究开发了基于近场通信技术的数据采集终端。该文分析了生鲜农产品供应链数据采集设备及工作环境的特点,开发一种基于近场通信技术（near field communication）、北斗系统（bei dou system）及全球移动通信系统（global system for mobile communications）集成技术的生鲜农产品供应链数据采集终端。该终端包含4个模块：NFC模块、系统CPU模块、北斗模块和GSM模块及电路系统。终端在写入数据时,同时将北斗加密数据通过NFC芯片PN532写入NFC标签,并通过GSM模块以短信的方式传递给后台数据库,利用RS232将数据信息传入节点企业平台,实现生鲜农产品数据信息的三重备份。该采集终端借助物联网及无线传感网的技术优势,实现生鲜农产品供应链各环节数据的自动智能采集并进行加密,满足企业在生产过程中不断变化环境下的数据采集及存储需求,该终端在极端环境下读取速度虽然降低了10%~25%,但存储率依然为100%,满足生鲜农产品供应链数据采集的需要,能够实现节点企业间信息连续度,为实现生鲜农产品可追溯提供参考。
