Remote Frequency Calibration Service at NMIJ

Transcription

1 Remote Frequency Calibration Service at NMIJ Case Example for APMP-WS 2014 Frequency Measurement Systems Section National Metrology Institute of Japan (NMIJ), AIST, JAPAN

2 Content Introduction Overview of remote calibration service at NMIJ Remote frequency calibration system between NMIJ and calibration labs Frequency stability of the calibration system Operational performance in the long run

3 Member of the Frequency Measurement Systems Section Kenichi Watabe Masato Wada Tomonari Suzuyama Atsuko Okuda

4 Background Regular Calibration Providing measurement-standards rapidly, economically and accurately by remote calibration technique.

5 Overview of remote calibration service at NMIJ

6 Remote frequency calibration service GPS common-view method Data transmission - Once or twice a day using SMTP protocol to the data server of NMIJ - Provide a calibration certification every month - Frequency Deviation and Standard Deviation are reported in every day's data The service has started between NMIJ and accredited calibration laboratories from January 2005.

7 Principle of frequency remote calibration GPS common-view method NMIJ, AIST GPS time T GPS GPS receiver Time difference measurement GPS receiver Time difference measurement T NMIJ T USER Ref GPS 1 = T NMIJ -T GPS Ref GPS 2 = T USER -T GPS Ref GPS 1 - Ref GPS 2 =T NMIJ -T USER

8 CMC of Remote Frequency Calibration Service Scope of calibration CMC (k=2) Condition Averaging time:1day Baseline:50 km 5 MHz, 10 MHz Averaging time:1day Baseline:500 km Averaging time:1day Baseline:1,600 km Claimed uncertainty in the case of L1 C/A code multi-channel GPS receiver

9 Current status of remote calibration service Number of users: 17 (on the rise year by year) Charge for service Base cost:167,900 JPY/Year (Monthly issue certificate) About :1,700,000 KRW (1 JPY 10 KRW) 10,000 CNY (1 JPY CNY) 50,000 NTD (1 JPY 0.3 NTD) 1,700 AUD (1 JPY 0.01 AUD) 50,000 THB (1 JPY 0.3 THB) etc. Initial cost:59,600 JPY for setting and adjustment

10 Remote frequency calibration system between NMIJ and calibration labs

11 Remote Frequency Calibration System by NMIJ GPS AIST(NMIJ) UTC(NMIJ) GPS Receiver jcss Calibration Certificate Registered establishment site Data server Web Published Data Data Download Data Upload Internet

12 Configuration of total remote frequency calibration system from NMIJ to end-user

13 Antenna Equipment GPS antenna for remote frequency calibration service GPS antennas Antennas for TWSTFT Air-conditioned Facility for TWSTFT (Converter & SSPA)

14 GPS receivers for remote calibration and public data (L1, C/A code) Measurement system for UTC(NMIJ)

15 NMIJ s CGGTTS data site Update every 15 minutes

16 Concepts of terminal unit at client sites (GCET : e-trace GPS Common-view Reference Signal Generator) (1) Easy operation, (2) Highly good cost/performance The terminal unit consists of Rb. oscillator or OCXO, GPS receiver module, CPU module, and 8 ports of reference signal distribution amplifier. (3) By sending obtained data at the client site to NMIJ or calibration lab. (using HTTP protocol with cryptography technology), calibration certifications will be provided from NMIJ or calibration lab. to clients. (4) Synchronization to UTC(NMIJ) The internal oscillator automatically synchronize to UTC(NMIJ) by monitoring the NMIJ's web site.

17 Synchronization to UTC(NMIJ) GPS Internal oscillator is synchronized to UTC(NMIJ) with the NMIJ web site data NMIJ 時間周波数国家標準 GPS 時刻比較受信機 Client terminal unit Internal oscillator Δt =Int. Osc. - GPS time Δt=UTC(NMIJ) - GPS time Δt=UTC(NMIJ) - GPS time NMIJ/AIST GPS data 公表サイト Update every 15 minutes internet 17

18 Inside of GCET Reference signal distributor Data processing main board Rb Osc. GPS module

19 Table 1. Main specifications of the device Main specifications of GCET GPS receiver Signal L1( MHz), C/A code Number of channels 12 channels Sensitivity < -135 dbm Positioning < 5 m Data acquisition interval 1 second Reference signal Input (optional) (option) 10 MHz Output 10 MHz: 8 ports +13 dbm ± 3 dbm 5 MHz: 1 port +13 dbm ± 3 dbm 1 pps: 1 port Time transfer Data format and schedule CGGTTS format by international time transfer schedule Reference Oscillator (Synchronized to UTC(NMIJ)) Communication interface Uncertainty Time and Frequency synchronization. Data transfer Rb-type OCXO-type < 5 ns : outside antenna < 20 ns : window-side antenna Synchronize to UTC(NMIJ) or UTC(k) using NMIJ's or Lab.(k) s data from NMIJ's or Lab(k) s web site, otherwise synchronize to GPS time HTTP protocol with cryptography technology < 1 1 day < 3 1 s < 5 1 day < 1 1 s Ethernet (10/100 BASE-T) and RS-232C

20 Frequency stability of output of GCET (on site)

21 Frequency stability of the calibration system

22 Demonstration Experiment GPS GPS GPS GPS HOKKAIDO TOHOKU KYUSHU KANSAI TSUKUBA Frequency National Standard receive data are transmitted via internet data is opened to NMIJ s web site OKINAWA

23 Evaluation Experiment at user site (1) GPS DO NMIJ DO OSAKA (Baseline 500 km)

24 Evaluation Experiment at user site (2) NMIJ DO Ext. signal (GPSDO) Ext. Signal (Cs) Gunma (Baseline 50 km)

25 Performance of Remote Calibration System HOKKAIDO, TOHOKU, KANSAI, KYUSHU, OKINAWA, NIMT (780 km), (255 km), (500 km), (930 km), (1590 km), (4620 km)

26 Operational performance in the long run

27 Detail of Client s Terminal Unit Item Mode Number GPS Receiver Cs Free run 3 2 JRC JQE102 1 GCET Rb NMIJ-DO 9 8 GCET 1 FT001 Rb GPS-DO 2 1 JRC JQE102 1 GCET Rb Free run 1 1 JRC JQE102 VCXO GPS-DO 1 JRC JQE102-VCXO

28 UTC-UTC(NMIJ) : Timescale

29 UTC-UTC(NMIJ) : Frequency deviation

30 Long-term properties of frequency remote calibration Cs(FreeRun), Rb(NMIJ-DO), Rb(GPS-DO)

31 5. Summary NMIJ started the remote frequency calibration service using GPS common-view method from The terminal unit (GCET) for remote frequency calibration using NMIJ-DO method was started from The main features of the terminal unit are; - low cost, also easy operation, - frequency source synchronized to UTC(NMIJ), - fully traceable frequency source. The long-term properties show stable results and these dependences of item and baseline length almost identical. These depend on the system and the installation environment(temperature, power line).

32 Thank you for your attention!