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== Station == === China === Freq: 68.5KHz Code: BPC Ops: NTSC https://en.wikipedia.org/wiki/BPC_(time_signal) <br> === Japan === Freq: 40KHz/60KHz Code: JJY Ops: NICT * http://jjy.nict.go.jp/ * https://en.wikipedia.org/wiki/JJY <br> === USA === Freq: 60KHz Code: WWVB Ops: NIST * https://en.wikipedia.org/wiki/WWVB * https://www.nist.gov/pml/time-and-frequency-division/radio-stations/wwvb <br> === England === Freq: 60KHz Code: MSF Ops: NPL * https://en.wikipedia.org/wiki/Time_from_NPL * http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-radio-time-signal <br> === German === Freq: 77.5KHz Code: DCF77 Ops: PTB * https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77.html * https://en.wikipedia.org/wiki/DCF77 * https://www.eecis.udel.edu/~mills/ntp/dcf77.html <br> === Swiss === Freq: 75KHz Code: HBG Ops: METAS * https://en.wikipedia.org/wiki/HBG_(time_signal) <br> == Format == === BPC === 载波 68.5KHz,脉宽调制 (Pulse-Width Modulation,PWM),码率 1 Hz 每个编码脉冲宽度为 0.1s,0.2s,0.3s 或 0.4s,分别代表四进制的 0,1,2,3。一串四进制的数字是由播发时刻的秒、时、分、星期、日、月、年插入几个校验位组成,长度为 20s [[文件:BPC-time-frame.png]] <br> <br> === JJY === 载波 40KHz 和 60KHz,脉宽调制 (Pulse-Width Modulation,PWM),格式类似美国 WWVB 码: [[文件:WWVB time code format.svg.png | 800px]] <br> <br> === WWVB === 载波 60KHz,脉宽调制 (Pulse-Width Modulation,PWM) 和 相位调制 (Phase Modulation, PM) [[文件:WWVB time code format.svg.png | 800px]] <br> <br> === DCF77 === 载波 77.5KHz,AM 和 PM https://en.wikipedia.org/wiki/DCF77 <br> == 解调芯片 == === CME8000 === * http://www.c-max.com.hk/assets/technology/rct/rct_ic/cme8000/CME8000-B17.pdf <br> === CME6005 === * http://aitendo3.sakura.ne.jp/aitendo_data/product_img/test/D606C/CME6005-A8-1.pdf <br> === DL6005 === * http://www.jfd-ic.com/Documents/DL6005.pdf <br> == Reference == * 可信时间戳服务:https://www.tsa.cn/ * 中科院国家授时中心:http://www.ntsc.cas.cn/kxcb/kpcg/shijian/201209/t20120921_3648661.html <br><br><br><br><br><br><br><br><br><br>
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