National Institute of Information and Communications Technology Development of the time...

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


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)


Japanese Low Frequency Standard Time and Frequency Transmission Stations (JJY)


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)


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


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. )


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


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


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


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.>


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 ]


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


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.


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.

National Institute of Information and Communications Technology Development of the time...

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