National Institute of Information and Communications Technology
Development of the time dissemination technology for the radio controlled
watches and clocks used by the network
Tsukawa Iwama, Fumimaru Nakagawa,Kuniyasu Imamura, Hiroshi Toriyama,
Akihiko Machizawa, and Hideo Maeno
National Institute of Information and Communications Technology
IntroductionNICT has distributed Japan Standard Time and national frequency standard. ↓ National serviceLow Frequency Standard Time and Frequency Transmission Stations in Japan (J
JY) / Radio controlled watches and clocks ↓ ProblemDifficult to receive radio waves in inappropriate environments such as inside of
buildings ↓ Correspondent methodPromotion of distribution in the network ↓ Plan of research and developmentDevelopment of the repeater using Network Time Protocol ( A small and prototype repeater ) ↓ Fundamental tests ( A field strength measurement and a functional
check )Utilization ・ Spread in JapanApplication ・ Spread in Southeast Asia, such as Thailand (Distribution of a local time)
National Institute of Information and Communications Technology
Japanese Low Frequency Standard Time and Frequency Transmission Stations (JJY)
National Institute of Information and Communications Technology
Various kinds of repeaters (relay system)
The conventional system• Booster system• Time link system• The relay system in a building• The system distributed to intranetThis system, Future system • Repeater system using NTP • The repeater system using HTTP (near
future)
National Institute of Information and Communications Technology
The conventional systemThe relay system in a building :The system which carries out frequency conversion of the received signal, and is indoors broadcast again by LF.
http://www.nippon-antenna.co.jp/news-release/jjy_sys.htm
Nippon Antenna
400 MHzTime link system :An original link system
SEIKO PRECISION INC.http://www.seiko-clock.co.jp/seiko/time.html
Receive40 kHz or 60 kHz
Transmission60 kHz or 40 kHz
Booster system :Frequency conversion and retransmission
CITIZEN HOLDINGS CO., LTD ( Rhythm Watch Co.,Ltd. )http://www.citizen.co.jp/
LF Stations
Standard time and frequency signal
Standard time and frequency signal
Standard time and frequency signal Antenna-installed
in rooftop of the building
Radio controlled watches and clocks
National Institute of Information and Communications Technology
Image of research and development plan for repeater
Home, Hotel, etc…
Repeater by NTP
NICTJST
InternetInternet
NTP server : NICT, NIMT, Public, etc.
Inside of buildings, underground, and …, inany countries with no LF station
Developed repeater
Ntp.nict.jp
Transmitting equipment for small areas(Inside of airport buildings, theme parks, universities corporate sites, and etc. )
National Institute of Information and Communications Technology
The subjects of development and utilization• Check the Extremely Low Power Radio Station• Make a presentation of the technical standard to
the clock industry in order to generalize the repeater using NTP. ( idea by NICT )
• Development of the model of a usable level• Make a proposal of application developed for the
repeater using a network ( For example : Wireless LAN, USB type, HTTP, and PLC (Power Line Communications) )
• Spread in Southeast Asia : in collaboration with NIMT, make a proposal of the repeater which is suitable for Thailand
National Institute of Information and Communications Technology
Development of prototype repeaters
• Developed in 2006 •At first, the prototype repeater generates
a time code on a personal computer (PC). Next, time information is sent out to the transmitting section and almost the same time code as JJY is transmitted from an antenna.•The timing from PC is maintained at the accuracy of NTP.•And the time code and timing which are received are sent to D/A of a transmitter.•A transmitter sends out Extremely Low Power from an antenna.•In this fiscal year, a basic check of operation is carried out.•In addition, We measured field strength.
coil type 3.2 cm
Transmitter
Loop type 34 cm
The antenna of two types is made as an experiment.
PC
NTP server
Antenna
Block diagram
National Institute of Information and Communications Technology
Small repeater development• Developed in 2006
The small repeater (one apparatus) was developed based on the know-how studies in the preceding year. The software developed with PC was becoming cheaper CPU of one chip. The NTP client operates with free software proprietary software. Therefore, repeater itself see to operate by connecting an Ethernet cable. On the other hand, We checked that the right time code was transmitted in the accuracy of NTP. Accuracy is less than 10 msec.
30 turns
National Institute of Information and Communications Technology
Field strength measurement• Commercial booster type repeater Is it transmitter with extremely low power?• Prototype repeater We measure FS with two kinds (a loop type and coil
type) of test antennas. We investigated whether it could use as Extremely Low Power Radio Station.
• Small repeater The performance of the loop antenna in a plastics
case needs to be checked.
<Field strength measurement used the large-sized electric wave darkroom.>
National Institute of Information and Communications Technology
The result of field strength measurement of a booster
40kHz60kHz
60kHz40kHz
Experiment scenery in a large-sized electric wave darkroom
電波法
●40kHz●60kHz
The formula in Radio Law of Japan(54-(24-log10F) [ dBμV/m ] )F is the frequency of the unit of MHz.
Three-set measurement
The maximum distance, which a radio controlled clock adjusts its time, is about 15m.
Japanese radio low
Distance [m]
Fie
ld S
tren
gth
[ dB
μV
/m ]
National Institute of Information and Communications Technology
The result of field strength measurement of a prototype
Diameter:34 cm
Diameter3.2 cm
Coil type Antenna
Loop type AntennaTurns 40kHz : 14 60kHz : 11
Range is about 20 m.
Japanese radio low
Distance [m]
Fie
ld S
tren
gth
[ dB
μV
/m ]
2007/06/04
Range is about 6 m.
Turns 40kHz : 88 60kHz : 66
National Institute of Information and Communications Technology
電波法●40kHz●60kHz
The result of field strength measurement of a small type
2008/8/14
2台測定
105 mm x 90 mm30 turns
Japanese radio low
Distance [m]
Fie
ld S
tren
gth
[ dB
μV
/m ]
Two-set measurement
Range is about 7 m.
National Institute of Information and Communications Technology
Conclusion• Development to the utilization level of a repeater
was achieved.• The check of Extremely Low Power transmitter
was performed.• The application sample in future was shown.• The clock companies started considering mass-
production.• NICT exhibited the small repeater to ITU Telecom
Asia 2008 in Thailand and National Science and Technology Fair 2009.
• NICT aims at spread in Southeast Asia of the radio controlled watches and clocks.