Takao Morikawa

National Institute of Information and Communications Technology

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森容

森川容雄

Mizuhiko Hosokawa

Juntendo University

Michito Imae

National Institute of Advanced Industrial Science and Technology

Hiroyuki Ito

Tokyo Institute of Technology

Masatoshi Kajita

The University of Tokyo

Noboru Kotake

National Institute of Information and Communications Technology

Kyoya Fukuda

National Institute of Technology, Niihama College

細瑞

細川瑞彦

Motohiro Kumagai

National Institute of Information and Communications Technology

伊宏

伊東宏之

Cooperative Institutions

National Institute of Information and Communications Technology

Ministry of Internal Affairs and Communications

Nippon Koei (Japan)

The University of Tokyo

Kyoto University

Anritsu (Japan)

Nagoya University

Communications Technology Laboratory

Tohoku University

National Astronomical Observatory of Japan

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原子周波数標準:セシウム1次周波数標準器.光励起型周波数標準器

Kyoya Fukuda Atsushi Hasegawa Hiroyuki Ito Motohiro Kumagai Noboru Kotake

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Design of a small sapphire loaded dielectric cavity for a space-borne hydrogen maser

IEEJ Transactions on Electronics Information and Systems (1999)

Takao Morikawa Y. Ohta Kenichiro Takahei Masaro Uehara M. Tsuda

For a space-borne hydrogen maser frequency standard, it is severely required to reduce the size and weight without degrading its excellent frequency stability. To meet these requirements, a small sized microwave cavity with high quality factor is necessary. In this paper, TE011 mode of a small sapphire loaded dielectric cavity for a space-borne hydrogen maser is analyzed and its design principle is discussed. The analysis shows that the frequency stability is optimized when the ratio of the outer diameter of the dielectric tube to the inner diameter of the cavity cylinder is about 0.5. The weight of the physics package is minimized when the diameter and the height of the cavity cylinder are equal to each other. The diameter or the volume of the cavity cylinder is determined by the frequency stability required in the application program.

Hydrogen maser

Microwave cavity

Cavity wall

Q factor

10.1541/ieejeiss1987.119.7_789

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Development and Performance Evaluation of Spaceborne Hydrogen Maser Atomic Clock in NICT

Hiroyuki Ito Takao Morikawa S. Hama

Hydrogen maser

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Determination of antenna factors using a three-antenna method at open-field test site

Hiroshi Masuzawa Teruo Tejima Katsushige Harima Takao Morikawa

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Frequency-Stability Measurement System Using High-Speed ADCs and Digital Signal Processing

IEEE Transactions on Instrumentation and Measurement (2007)

Ken Mochizuki Masaharu Uchino Takao Morikawa

We propose a novel measurement system that evaluates the frequency stability of high-precision oscillators such as atomic oscillators. This measurement system consists of a pair of high-speed analog-to-digital converters (ADCs) and digital-signal-processing (DSP) circuits on a field programmable gate array. The pair of high-speed ADCs simultaneously digitizes the two sinusoidal-voltage outputs from the oscillator under test and a reference oscillator. The DSP circuits calculate the phase difference between the two sinusoidal voltages. The frequency stability evaluated as the Allan deviation sigmay(tau) is calculated from the phase difference. The main advantage of this system is that the hardware configuration is much more compact than the conventional systems using a dual mixer and a local oscillator. Nonetheless, the system noise floor of the prototype at the nominal frequency of 5 MHz is sigmay(1000 s) = 6.8 times 10 ^-17 , which is sufficient to evaluate a commercial hydrogen maser oscillator and is better by a factor of 5 than our previously reported system. We have verified that the measurement accuracy of the prototype depends on the nominal frequency and the level of the sinusoidal voltages, but it does not depend on the initial phase difference and offset frequency.

Allan variance

Hydrogen maser

Crystal oscillator

Digitally controlled oscillator

10.1109/tim.2007.895588

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Citations (32)

Accuracy evaluation of optically pumped primary frequency standard CRL-O1

Metrologia (2004)

Atsushi Hasegawa Kyoya Fukuda Masatoshi Kajita Hiroyuki Ito Motohiro Kumagai

In cooperation with the Time and Frequency Group of the National Institute of Standards and Technology, the Communications Research Laboratory has developed an optically pumped primary frequency standard (PFS) which is named CRL-O1. The accuracy of CRL-O1 has been evaluated and reports have been sent to the Bureau International des Poids et Mesures. The results of the evaluations have been published in Circular T. We estimate the biases of the frequency shifts and the so-called type A and type B uncertainties. The combination of type A and type B uncertainties is about 7 × 10−15. The evaluated frequency of CRL-O1 is in good agreement with that of other PFSs.

Frequency standard

Standard uncertainty

10.1088/0026-1394/41/4/006

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Generation and dissemination of time and frequency standard: Development of the trusted time stamping system

Tsukasa Iwama Noriyuki Kurihara Michito Imae K. Imamura Noboru Kotake

Standard time

Stamping

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International time transfers via GPS.

The Journal of the Japan Society of Aeronautical Engineering (1987)

Kazuyuki Yoshimura Makoto Urazuka Michito Imae Chihiro Miki Takao Morikawa

Time transfer

10.2322/jjsass1969.35.43

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Time and Frequency Keeping and Its Distribution System at CRL

ptti (1996)

Michito Imae Mizuhiko Hosokawa Yuko Hanado K. Imamura Atsushi Otsuka

Abstract : As a national frequency standards laboratory in Japan, Communications Research Laboratory (CRL) is doing research and development work on a primary frequency standard. Besides the primary standard, CRL is in charge of the generation of local UTC, UTC(CRL), and its time and frequency distribution via HF and LF radio signals, telephone line, and computer network. CRL contributes to TAI not only atomic clock data, but also as one of the node laboratories of the international GPS time transfer network of the BIPM. For this purpose CRL is studying the GPS ionospheric measurement system and two-way time transfer using communication satellites. In this paper we will present activities on time and frequency standards at CRL.

Frequency standard

Time transfer

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Atomic frequency standards: Hydrogen maser

Hiroyuki Ito Mizuhiko Hosokawa Jun Umezu Takao Morikawa M. Tsuda

Hydrogen maser

Frequency standard

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