COMMISSION A : Electromaganetic Metrology (November 2007 - October 2010)
Edited by Masatoshi Kajita and Yasuhiro Koyama
A1. Time and Frequency Standards and Time Transfer Technique
NICT has developed a cesium atomic fountain primary frequency standard NICT-CsF1. [Circular T, Kumagai et al., 2008a, b]. The typical uncertainty was 1.5 ~ 10-15 including the uncertainty of the link. To improve the short-term stability of NICT-CsF1, the authors have introduced the cryogenic sapphire oscillator (CSO), which developed in the University of Western Australia. The stability improved by a factor of 3. And, to reduce the systematic uncertainty, the authors have started to develop our second atomic fountain (NICT-CsF2). So far, the authors have succeeded to observe 0.95Hz Ramsey signal in NICT-CsF2.
NICT newly developed a Network Time Protocol (NTP) server with high-performance and started a public time service from 2007. The number of access was about fifteen million per day in 2007 and is more than one hundred million per day in 2010. A new protocol for high-speed network time transfer has been investigated by using this server. NICT also developed a GPS receiver with network for a remote calibration and time transfer [Machizawa et al. 2008] and reconstructed more convenient system [Iwama et al. 2010]. Then NICT transferred the technology of a GPS receiver to a commercial company.
NICT is regularly performing Two Way Satellite Time and Frequency Transfer (TWSTFT) between Germany (PTB) and Asian T&F institutes (KRISS, TL, NTSC, SPRING, and NMIJ), and calibrated their station delays for TL, KRISS and NMIJ. Obtained data by TWSTFT and GPS are reported to BIPM. The TWSTFT data for NICT/PTB link has been adopted for TAI link since April 2007 in place of GPS data. The number of participants of this Asia-Eu link sharply increased. At last 6 Asian and 2 European institutes (NICT, KRISS, NMIJ, TL, NTSC, NIM, PTB and OP) joined. After the link pause for half year due to the satellite malfunction, the link restarted by switching the satellite on October 2010. Causes of observed diurnal variation have been studied, especially compared before and after the switch.
By the install of a relay station in Hawaii, the link between NICT and USNO was established by 2-hop connection on July 2010. The result shows good agreement with GPS PPP.
NICT developed a new TWSTFT modem using Dual Pseudo-random Noise (DPN) signal. NICT carried out TWSTFT experiments with DPN signal between NICT and TL, as well as confirmed that short (< 100 sec) and long (< 1 day) term stability of the DPN system were less than 50 ps and less than 200 ps respectively. DPN method was also adopted for QZSS narrow band bent pipe system, and used for time comparison between NICT Koganei and Okinawa earth stations. NICT developed GPS carrier phase time transfer software gconcerto version 4h. The software can analyze both methods, PPP and single difference observations, and be used for the evaluation of DPN method. The results of DPN and GPS carrier phase were consistent within 100 ps per 1 day.
NICT developed an RF distribution system using optical fibers, which has an active phase-noise cancellation system. The system was evaluated in the JGN2plus optical fiber link which was an urban optical fiber link in Tokyo [Fujieda et al. 2009]. The transfer stability in the 10-18 level at an averaging time of 1 day was achieved in the 114-km frequency dissemination [Kumagai et al. 2009]. In addition, the transfer length was extended to 204 km by a cascaded system, which stability was still in the 10-17 level [Fujieda et al. 2010]. For direct comparison of optical clocks, an optical carrier transfer system has been developed, too. Two 87Sr optical clocks were compared using a 60-km optical fiber link in the 10-16 frequency resolution. Its short term stability in the 10-15 level enabled us the real time detection of the frequency difference of 10 Hz.
NICT achieved pico-second order precision for two-way time and frequency comparison between the ground clock and the on-board atomic clock on ETS-8 satellite, which was launched in December 2006. Both code phase and carrier phase showed consistent result and capability to monitor the on-board atomic clock. [Takahashi et al. 2008]
NICT developed the time management system, which consists of on-board equipment and the ground segment of the Quasi-Zenith Satellite System (QZSS) which is a regional satellite navigation system in Japan. Its first satellite QZS-1 was successfully launched on September, 2010. Various experiments such as precise T&F comparison between the QZS-1 and UTC(NICT) and between two ground stations, on-board atomic clock monitoring, L-band calibration, are now been carrying out [Hama et al. 2009]
In NMIJ, following researches have been conducted.
Primary Frequency Standards; NMIJ has made the calibration of the International Atomic Time (TAI) 18 times between 2007 and 2010 with the Cs atomic fountain frequency standard, NMIJ-F1 with a combined uncertainty of 3.9x10-15 [Circular T, Yanagimachi et al. 2008, Takamizawa et al. 2010]. NMIJ-F1 will be used as a reference oscillator for the evaluation of the optical lattice clocks in NMIJ, the development of our second fountain (NMIJ-F2), as well as used for the TAI contribution. The construction of NMIJ-F2 has been continued. A truncated atomic beam fountain was proposed and the proof of the principle experiments has been started, in order to achieve a low collisional frequency shift, high frequency stability and the uncertainty of the order of 10-16 [Takamizawa et al. 2010].
Ultra-stable microwave oscillator; NMIJ has been maintaining two cryogenic sapphire oscillators (CSOs) for use as a local oscillator of Cs atomic fountains and a reference oscillator for the evaluation of ultra-stable lasers in optical lattice clocks.
Time Keeping; Four cesium atomic clocks with high-performance beam tubes (Agilent 5071A) and four active hydrogen maser frequency standards are operated for time keeping in NMIJ. One of the hydrogen maser frequency standards has been used for the generation of UTC(NMIJ) since March 2006 to improve the short term stability of UTC(NMIJ).
Time and Frequency Transfer; In NMIJ, dual frequency carrier phase GPS receiver is one of the main international time and frequency transfer tools. In addition, NMIJ has the Two Way Satellite Time and Frequency Transfer (TWSTFT) facilities for Asia Pacific link and for Asia-European link.
An optical fiber bidirectional frequency transfer system using Wavelength Division Multiplexing technology is also studied in NMIJ as one of future precise time and frequency comparison systems [Amemiya et al. 2006, Amemiya et al. 2010a, Amemiya et al.2010b].
Frequency Calibration Service; NMIJ and related organizations have been conducting to construct remote calibration systems for several metrology areas since 2001. Time and frequency division of NMIJ has been developing a frequency calibration system using GPS common-view method and Internet. NMIJ's remote frequency calibration service has been started since 2006 to the calibration laboratories. NMIJ has also started to develop the user equipment for the end users of the remote frequency calibration service [Imae et al. 2010]. A simple and cost effective frequency dissemination method also has been developed in NMIJ. In this method, optical fiber network service (INS-1500) is used for generating 10 MHz reference signal. Stability test results showed a good performance with an uncertainty of less than 1~10-12 at an averaging time of one day [Amemiya et al. 2008].
A2. Laser Stabilization and Frequency Measurement
The researches and developments in Japan on the stabilization of lasers and the optical frequency measurement are also mainly carried out in the National Institute of Information and Communications Technology (NICT) and National Metrology Institute of Japan (NMIJ), together with some very active universities.
NICT is developing a single Ca+ ion trap optical frequency standard. Matsubara et al. have measured the absolute frequency of the 4s2S1/2 - 3d2D5/2 forbidden transition, and the frequency uncertainty is reduced down to 5 Hz [Matsubara et al., 2008 a,-c, 2009 a-b].
NICT is developing also an optical frequency standard based on the Sr 1S0 - 3P0 forbidden transition in a optical lattice. The frequency uncertainty is of the order of 0.2 Hz [Yamaguchi et al. 2010 a].
Li et al. developed clock lasers with linewidth narrower than 3 Hz [Li et al. 2008 1.-b, 2010 a]. Also the new system to transfer the stable laser frequencies to a distant place via optical fibers [Fujieda et al. 2009, Kumagai et al. 2008 c, 2009].
To measure the laser frequency, NICT has operated two optical frequency combs based on Ti:Sapphire laser with the uncertainty at 10-17 level [Nagano et al., 2009] and is developing fiber laser frequency combs . The fiber combs measure their relative frequency stability and estimate the stability as 5x10-13 and 1x10-15 at averaging time of 1 s and 500 s respectively.
The Allan variance of the ratio between Ca+ - Sr transition frequencies was measured to be 3 x 10-16 with the measurement time 2000 sec.
Various time and frequency standards related researches have been conducted in NICT and some Universities, such as on atomic and molecular physics. Kajita has proposed an infrared frequency standard based on the vibrational transition frequencies of magnetically trapped XH and XLi molecules, and XH+ molecular ions (X: even isotopes of group II atoms) [Kajita 2008 a,b, 2009 a-b, 2010].
NMIJ is developing an 171Yb optical lattice clock. They have succeeded in the first absolute frequency measurement of the 1S0 - 3P0 clock transition of 171Yb with an uncertainty of 5.4 x 10-14 [Kohno et al. 2009]. Progress is under way to reduce the uncertainty by increasing the signal to noise ratio of the observed spectrum using the atom number normalization scheme. They have developed a fiber-comb-stabilized light source at 556 nm for magneto-optical trapping of ytterbium, which is necessary for obtaining ultracold ytterbium atoms trapped in an optical lattice [Yasuda et al. 2010]. NMIJ has also started a new project on Yb/Sr dual optical lattice clock project in 2009. They developed a compact light source for 1st stage cooling of Sr using a periodically poled lithium niobate waveguide [Akamatsu, et. al. 2010] and successfully magneto-optically trapped both species in the same chamber. NMIJ has developed advanced optical frequency combs based on erbium-doped fiber laser (fiber comb). Robustness, usability, and servo bandwidth has been improved. For example, NMIJ have established the national standard of length in Japan by using a fiber comb. On the other hand, a fiber comb with mHz-level relative linewidth was realized using an intra-cavity electro-optic modulator [Nakajima et al. 2010]. They utilized the narrow linewidth fiber comb to develop the light source for the clock transition of Yb and the 2nd stage cooling of Sr. In the clock laser system, the highly stabilized fiber comb is able to transfer the linewidth and frequency stability from one laser frequency to another and it plays a role of an ultra-stable local oscillator for multi wavelengths. The clock laser at 578 nm for the Yb optical lattice clock has been phase locked to one of the comb modes. The authors have demonstrated spectroscopy of the clock transition in Yb atoms with the new clock laser system.
Katori group at University of Tokyo developed lattice clocks using 87Sr and 88Sr [Akatsuka et al. 2008]. Takamoto et al. discussed also the possibility to trap Sr atoms with a blue detuned laser [Takamoto et al. 2009]. Hachisu et al. started to develop an Hg optical lattice clock [Hachisu et al. 2008].
The frequency transfer between Katori group and NMIJ, that made possible to compare the Sr lattice clock and NMIJ-F1 [Hong et. Al. 2009]. In 2010, the direct frequency comparison between Sr lattice clocks in Katori group and NICT was performed.
A3. Realization of Electrical Units (DC & LF)
Research works and developments on dc and low frequency electrical standards, that is, standards for dc voltage, dc resistance, ac resistance, capacitance, inductance, ac/dc transfer etc., are implemented in Electricity and Magnetism division of National Metrology Institute of Japan (NMIJ), partly in collaboration with several other institutes in Advanced Industrial Science and Technology (AIST).
NMIJ has been developing a pulse-driven (10 mV, rms) and programmable (3 V, rms) Josephson arbitrary waveform synthesizers (JAWS) based on the over-damped Josephson junction arrays (JJAs). NMIJ has adopted pulse-tube-type mechanical cryocoolers and newly developed wide band chip carriers for this project. The cryocoolers have extremely low mechanical noise and the chip carriers are equipped with 20 or 32 coaxial inputs/outputs of which the outer conductor are electrically separated to suppress ground loop noise [Kaneko et al. 2010, Urano et al. 2009a, 2009b, Maruyama et al. 2009, Maruyama et al. 2010].
Devices of quantum Hall array resistance standard (QHARS) with a nominal value close to 10 k¶ on the i = 2 plateau have been developed on a GaAs/AlGaAs hetero-substrate. This QHARS device consists of just 266 Hall bar elements, and its nominal value has only 0.0342 ppm difference based on RK-90 from the integer value of 104. As a result of comparison measurement with the conventional Quantized Hall Resistance Standard via a 100-¶ standard resistor, the difference between the measured value and nominal value is less than the uncertainty level of 1.0 ~ 10-8. We plan to fabricate and evaluate several types of QHARS devices and confirm the reliability of the devices [Oe et al., 2008, 2010a].
Stable standard resistors (1 ¶ to 10 k¶) are now being developed in collaboration with Alpha Electronics. 100-¶ standard resistors of which temperature coefficients are extremely low, less than 0.1 ppm/degree, and resistance values are greatly stable, less than 0.1 ppm/year have been successfully manufactured and in market. Resistors with other nominal values are also under development [Sakamoto, Y et al., 2010].
Capacitance standards from 10 pF to 1000 pF are established at NMIJ based on the Quantized Hall Resistance at dc with an ac/dc calculable resistor and a quadrature bridge [Nakamura et al., 2010]. NMIJ has planned to derive the capacitance values from the AC-QHR in the future. The new quadrature bridge to link capacitance to the AC-QHR is now being developed [Oe et al., 2010b]. Higher values of capacitance with dissipation factor from 0.01 ÊF to 10 ÊF are also established at NMIJ using a four-terminal-pair (4TP) impedance bridge with a 10:1 voltage ratio transformer.
NMIJ has developed a capacitance-scaling bridge using a current comparator and an inductive voltage divider for calibrating 4TP-defined capacitance standards of 100 ÊF. The expanded uncertainties of the capacitance and the dissipation factor of 100 ÊF at 120 Hz are 11 ÊF/F and 14 Êrad, respectively. The bridge was recently modified aiming to calibrate the standards of 1 mF. Estimations of the uncertainties of 1 mF are now in progress [Sakamoto, N et al., 2010].
NMIJ has provided ac-dc voltage difference transfer calibration of thermal converters in the voltage range from 10 mV to 1000 V and in the frequency range from 10 Hz to 1 MHz. Practical thin film multi-junction thermal converters (MJTC) have been also developed in collaboration with NIKKOHM Co. Ltd. Our device has the thermoelectric transfer difference of better than 0.2 ÊV/V and frequency characteristics of the ac-dc transfer differences were considerably improved in the range between 10 Hz and 1 MHz [Sasaki et al., 2010]. NMIJ has developed AC voltmeter calibration system by using a planar MJTC in the frequency range from 40 Hz to 100 kHz and at the voltage of 10 V [Amagai et al., 2010]. NMIJ has planned to extend the frequency range down to 5 Hz and the voltage range down to 1 V. Also, we have been developing a planar MJTC for improving low-frequency characteristics below 100 Hz and the long-term stability. Employing a new thermopile pattern, the stability of the planar MJTC has been improved.
NMIJ has developed a harmonic voltage and current measurement standard. The standard has been confirmed that it has the uncertainty level of 40 ppm - 80 ppm up to 50th harmonics by means of using AC calibrators as AC reference standards. The feasibility of a power measurement capability of the standard has also been confirmed that it has uncertainty level of 20 ppm in the comparison of a power meter between Japan Electric Meters Inspection Corporation (JEMIC) and NMIJ [Yamada et al., 2010].
NMIJ has developed a calibration system for the AC shunt standard of the current range from 1 A to 10 A and the frequency range from 50 Hz to 400 Hz [Kon et al., 2010].
A4. EM field, Power density and antenna Measurement
A dipole antenna is a simple linear antenna, and this result in the accuracy and high-selectivity of the field polarization. Since many electromagnetic compatibility /electromagnetic interference (EMC/EMI) measurements below 1 GHz are implemented on a ground plane, responses of the antenna employed in these measurements should contain the effect of the coupling with image. However, free space antenna factor (AF) is often used for the measurements even above the ground plane, and errors are introduced by few decibels especially at lower frequencies. To overcome this problem and considerable efforts in the measurements, a prediction method of the height-dependent AF and mismatch effects have been proposed [Morioka et al. 2010b]. Measurements in an anechoic chamber become common above 1 GHz. Some EMC test regulations require measurements in this frequency range. Since the measurement environment is quasi-free space, the free space AF of the antenna should be calibrated. The three-antenna method is applied and the calibration capability has been achieved to 0.4 dB (k=2) in the frequency range from 1 to 2 GHz [Morioka 2009 a].
Although the field generation in an anechoic chamber has an advantage in the frequency band, that in a transverse electromagnetic (TEM) waveguide is still useful in terms of compactness. In addition to this, generating a strong field in the TEM waveguide requires an amplifier with significant lower gain compared with that in an anechoic chamber. Accordingly, it is reasonable to use a TEM cell at a lower frequency than the higher order mode cutoff frequency of the cell. For the use of a TEM cell as a standard field generator, the electromagnetic fields of the cell should be accurately evaluated. A method to measure electromagnetic fields in a TEM cell by using a passive scatterer has been proposed [Morioka 2009 b]. Since the E-field of a TEM cell varies with respect to the location, probe responses to such a non-uniform E-field have been investigated [Morioka 2010a].
A continuous antenna factor in a wide frequency range is convenient to be used and such a broad-band antenna as a log-periodic antenna (from 300 MHz to 1 GHz) and a bi-conical antenna (from 30 MHz to 300 MHz) were evaluated for a metrology standard. A new method was proposed for evaluating a free-space antenna factor continuously through a wide frequency band. The method is based on a technique of a time-domain analysis and a pulse-compression technology for reducing the influence by the reflected waves from surrounding obstacles. The method was examined for calculating the free-space antenna factor of a log-periodic antenna and a bi-conical antenna widely used for EMI measurement [Kurokawa et al. 2009, 2010a].
The developments of calibration techniques for loop antennas were carrying out by AIST. AIST started to develop the calibration method since 2002. AIST has been providing a calibration service for small loop antennas whose diameters are about 10 cm and 60 cm in the frequency range from 9 kHz to 30 MHz since 2007. This calibration service was expanded in March in 2008. The target of the loop antennafs diameter is 133 mm and the frequency range is from 20 Hz to 200 kHz. Basically they calibrate the standard loop antenna by the g3-Antenna Methodh and the customerfs loop antennas by the gReference Antenna Methodh. They also studied and proposed another more simple reference calibration method for loop antenna [Ishii et al. 2009a].
The developments of calibration techniques for short monopole antennas were carrying out by AIST. They proposed g3-Antenna Method [Ishii et al. 2009b]h and gReference Antenna Method [Ishii et al. 2010]h for short monopole antenna. These studies are in progress.
AIST started to develop AC magnetic field strength standard since 2008. They will start the calibration service at 50 Hz, 55 Hz, and 60 Hz in 2011. The method depends on the gStandard Field Methodh using a Helmholtz-coil. On the other hand, NICT and Aoyama Gakuin University are also developing the magnetic field sensor calibration system.
Calibration services for the gains of standard horn antennas are being performed from 1 GHz to 40 GHz at specified 21 frequency points using transfer method. An antenna gain calibration service for micro-wave standard gain horn antenna (1.7 GHz to 2.6 GHz) has been prepared using a planer near-field antenna measurement method. An antenna factor calibration service for ridged guide broadband horn antenna (1 GHz to 6 GHz) will be started from March 2011.
For expanding the frequency range of antenna gain standard, we have developed a calibration system for V-band (50 GHz to 75 GHz) millimeter-wave horn antenna using the three antenna extrapolation method. In the conventional extrapolation method, the multiple reflections between antennas are removed by the moving average method. To reduce the long measuring time caused by the moving average, the time-domain gating method was employed for removing multiple reflections [Ameya et al. 2010 a].
A novel method was proposed in antenna measurements [Hirose et al. 2010]. The method realizes antenna measurements in full 2-port calibration that requires only open-short-load calibration at each port without through calibration because of using the unknown thru algorithm. The residual systematic errors are completely equivalent to the conventional unknown thru method. No need to do through calibration is especially important in antenna measurements because we are released from the hard labor to mate cable connectors directly or to other cable connectors.
In the EMC field, the frequency range of the EMI regulation is expanded from 1 GHz to 6 GHz in EU and Japan in 2010. To improve the EMI anechoic chamber performance above 1 GHz, we have proposed a new anechoic chamber evaluation technique using plane-wave spectrum for finding the reflection points in EMI anechoic room [Ameya et al. 2010 b]. The proposed method enables to obtain the intensity and the angle of arrival of reflection waves and facilitates improving performance of anechoic chambers.
Kurokawa et al. have developed an EMI measurement system using microwave photonic technologies. It has the function of a kind of directional findings for interferences in, for example, an anechoic EM chamber [Kurokawa et al. 2010 b]. The system can be used from 30 MHz to 6 GHz.
Capozzoli et al. have developed planar and spherical scanner systems for near- field antenna measurement using photonic sensors that are a few of grams in weight and a few of millimeters long. The systems are available about below 10 GHz. The authors have launched a collaborative research with Napoli Federico II University in Italy for the phase-less near-field antenna characterization using such photonic sensors as above mentioned [Capozzoli et al. 2009, 2010].
A5. Power, Attenuation and Impedance Measurement
In recent years, NMIJ has started to study and develop a new microwave power standard based on quantum electronics. The new microwave power standard is directly linked with frequency measurement via atomic Rabi frequency. The Rabi frequency of cesium atoms in a glass cell inserted in a WR-90 waveguide was measured. Then, the magnetic field strength of the microwave was estimated from the measured Rabi frequency in 2008 [Kinoshita et al., 2008a, 2008b, 2008c, 2009a, 2009b, 2009c, 2009d]. The magnetic field strength was converted into the microwave power using an analysis of the distribution of the electromagnetic field in the waveguide [Kinoshita et al., 2010a]. It was confirmed that the microwave power measured from the Rabi frequency is consistent with that measured by a calorimetric method within their uncertainties [Kinoshita et al., 2010b, 2010c]. Now, the authors are improving the uncertainty by developing a new glass cell.
In high precision attenuation measurements and standards, the mismatch is often the largest term contributing to the systematic uncertainty. To minimize this uncertainty a RF attenuation measurement technique, where the source and load do not have to be matched to the line impedance, was proposed [Widarta et al, 2008a, 2009a]. The technique based on the cancellation of the multiple reflected signals in the network by performing additional loss measurement steps to the device under test (DUT), which are fitted to quarter-wavelength (QW) lines. The QW lines reverse the directions of the vectors of the reflected signals, and then the effects of the mismatch are approximately canceled. This technique has the ability to measure attenuations of discrete frequencies at which the relative phase shift values of the lines to the frequencies are 90[deg]. Improvement to the system was done, by introducing two low-reflective lines (airlines) where the phase shift values are already-known instead of the QW lines, in order to extend the capability to measure RF attenuation in broad continuous frequencies [Widarta et al, 2010]. A simple IF receiver system dedicated for working standard system of attenuation has been also developed by employing a calibrated resistive step-attenuator assembly at 30 MHz as an IF reference standard and a general-purpose receiver as a sensitive level detector [Widarta, 2008b].
NMIJ participated as a linking laboratory in the APMP comparison of attenuation at 60 MHz and 5 GHz (APMP.EM.RF-K19.CL) [Gao et al, 2010].
Calibration service for RF attenuation in the frequency range of 50 - 75 GHz (V-band) was started to meet the demands for accurate and traceable measurement in the industry. A new primary attenuation standard for the V-band was developed [Iida et. al. 2010]. Based on the IF substitution method, it employs an inductive voltage divider (IVD) working at 10 kHz as a reference standard. A highly stable IF signal is obtained for precision measurement using phase-lock technology on the frequency-converted local signal.
For the noise standard, an original cryogenic standard noise source with WR90 waveguide flange was constructed in the frequency range of 8-12 GHz [Iide et. al. 2008, 2009a]. The noise temperature and uncertainty of the noise source were evaluated by a sliding short method using a total-power radiometer. In order to expand the frequency range of the standard noise source, NMIJ was also developed a cryogenic 7-mm coaxial noise source and its evaluation method [Iida et. al. 2009b]. The noise temperature of the coaxial noise source was calibrated by using an auxiliary transmission line. The contribution of the noise generated from the transmission lines was estimated by the available power ratio of the transmission line and the radiometer measurements in particular conditions.
NMIJ has started the joint research project with National Physical Laboratory, UK. In the collaborative work, it is clear that the dimensional calibration capabilities of coaxial air line, i.e. 3.5 mm line size and 1.85 mm line size, were good agreement between both laboratories [Horibe et al., 2007, 2008c, 2010a]. Then NMIJ and NPL had been developed the verification method of phase measurements in the vector network analyzers (VNA) [Horibe et al., 2009a]. In addition, NMIJ and NPL developed a new concept of VNA calibration standards, i.e. eAir Openf standards [Horibe, et. al., 2010e]. The NMIJ showed the calibration and measurement capabilities for air line dimensions of 1.0 mm line size [Horibe et al., 2008a, 2009a]. The evaluation infrastructure for the connector interface to estimate electrical characteristics of air line, then NMIJ shows a characteristic depends on the connector dimensions, i.e. male pin and female socket, [Horibe, 2008b]. The calibration services of the complex voltage reflection coefficients, in the frequency range of 9 kHz to 18 GHz, have been started for PC7 connector in 2010 [Horibe et al., 2009e, 2010b]. These calibration cervices are based on use of the originally-designed standard terminations in the range of 9 kHz to 10 MHz, then, the long length air lines as the impedance standards are calibrated using a dimensional measurement and electrical loss measurement [Horibe et al., 2010b]. In 2009, the development of the scattering parameter standard for the rectangular waveguide in the frequency range of 50 GHz to 330 GHz, have been started [Horibe et al., 2010c, 2010d. Subsequently, in 2010, the originally-designed waveguide flanges and calibration standard were developed and evaluated.
Circular T 236, 237, 238, 242, 243, 244, 245, 248, 249, 251, 253, 254, 255, 256, 257, 258, 259, 263, 264, 265, 270, 272, 273, published by BIPM in 2007, 2008, 2009, ,and 2010.
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Gao Qiulai, Liang Weijun, Joo-Gwang Lee, Anton Widarta, Michael W K Chow, Thomas Wu5, Stephen Grady, Mariesa Prozesky, Erik Dressler, Kamlesh Patel, P S Negi, Chairat Wichianmongkonkun and Massinee Chanvichitkul, gFinal report on APMP attenuation key comparison APMP.EM.RF-K19.CL: Attenuation at 60 MHz and 5 GHz using a Type N step attenuatorh, Metrologia, 47, Tech. Suppl., 01015, 2010
Hachisu H., K. Miyagishi, S. G. Porsev, A. Derevianko, V. D. Ovsiannikov, V. G. Pal'chikov, M. Takamoto, and H. Katori, gTrapping of neutral mercury atoms and prospects for optical lattice clocksh, Phys. Rev. Lett., Vol. 100, 053001, 2008
Hachisu H., K. Miyagishi, S. G. Porsev, A. Derevianko, V. D. Ovsiannikov, V. G. Pal'chikov, M. Takamoto, and H. Katori, gTrapping of neutral mercury atoms and prospects for optical lattice clocksh, Phys. Rev. Lett., Vol. 100, 053001, 2008
Hirose M. and K. Komiyama, gA novel full 2-port calibration method for antenna measurement using SOL standards without through procedureh, in CPEM2010 Dig. pp.329-330, Daejeon, Korea, June 2010
Hong F.-L., M. Musha, M. Takamoto, H. Inaba, S. Yanagimachi, A. Takamizawa, K. Watabe, T. Ikegami, M. Imae, Y. Fujii, M. Amemiya, K. Nakagawa, K. Ueda, and H. Katori, gMeasuring the frequency of a Sr optical lattice clock using a 120-km coherent optical transferh, Optics Letters vol. 34, pp. 692, 2009
Horibe,Masahiro., [2005a], A survey of RF & microwave impedance standards, AIST Bulletin of Metrology, vol.3, no.4, pp.625-632 (in Japanese)
Horibe M. and N. Ridler, gUsing time-domain measurements to improve assessments of precision coaxial air lines as standards of impedance at microwave frequenciesh, 70th ARFTG conference digests, 2007/12
Horibe M., M. Shida, and K. Komiyama [2008a], gA CALIBRATION FOR PRECISION COAXIAL AIR LINES USED IN THE FREQUENCY RANGE UP TO 110 GHzh, CPEM2008 conference digests, pp.478-479, 2008/06
Horibe M., M. Shida, and K. Komiyama [2008b], gQuantitative Understanding of the Mated Interface Characteristics of Precision Coaxial Connectors at Microwave and Millimeter-Wave Frequenciesh, 008 IEEE MTT-S International Microwave Symposium Digest, pp.120-130, 2008/06
Horibe M. and N. Ridler [2008c], gA BILATERAL COMPARISON OF MEASUREMENT OF DIAMETERS AND CHARACTERISTIC IMPEDANCE OF PRECISION 3.5 mm COAXIAL AIR LINESh, CPEM2008 conference digests, pp.474-475, 2008/06
Horibe M., M. Shida, and K. Komiyama [2008d], gTime-domain and mechanical assessments of 1.0 mm coaxial air linesh, ARFTG 72nd Microwave Measurement Symposium Proceedings, pp.26-36, 2008/12
Horibe M. and N. Ridler [2009a], gComparison between Two National Metrology Institutes of Diameters and Characteristic Impedance of Coaxial Air Linesh, IEEE Trans. Instrum. Meas, 58-4, pp.1084-1089, 2009/03
Horibe M., M. Shida, and K. Komiyama [2009b], gDevelopment of Evaluation Techniques for Air Lines in 3.5 mm and 1.0 mm Line Sizesh, IEEE Trans. Instrum. Meas., 58-4, pp.1078-1089, 2009/03
Horibe M. [2009c], gMetrological Traceability in Vector Network Analyzer Measurementsh, Thailand-Japan MicroWave (TJMW2009) Digests, pp.141-144, 2009/08
Horibe M. and N. Ridler [2009d], gVerifying Transmission Phase Measurements at Millimeter Wavelengths Using Beadless Air Linesh, 74th ARFTG Microwave Conference Digests, 2009/12
Horibe M. and N. Ridler [2010a], Bilateral Comparison of 1.85 mm Coaxial Air Line Dimensional and Characteristic Impedance Measurements Between NPL and NMIJ, CPEM2010 conference digests, 2010/06
Horibe M., M. Shida, K. and Komiyama [2010b], gNational Metrology Standards of Scattering Parameter at Radio Frequencyh, CPEM2010 digests, 2010/06
Horibe M., M. Shida, and K. Komiyama [2010c], gTraceability of S-parameter Measurement of Waveguide Devices in the Range of Millimeter Wave Frequency from 75 GHz to 325 GHzh, AP-RASC'10 digests, 2010/09
Horibe M., M. Shida, and R. Kishikawa [2010d], gComplete Characterization of Rectangular Waveguide Measurement Standards for Vector Network Analyzer in the range of Millimeter and Sub-millimeter wave frequenciesh, The 76th ARFTG Microwave Measurement Symposium, 2010/12
Horibe M., N. Ridler, M. Salter, and C. Eio [2010e], gCharacterization and Verification of Coaxial Open-circuit Primary Standards for Millimeter-wave Vector Network Analyzer Calibrationh, The 76th ARFTG Microwave Measurement Symposium, 2010/12
Iida H., Y. Shimada and K. Komiyama, gAn experimental evaluation of a cryogenic noise source by a sliding short method in the frequency range of 8 GHz to 12 GHz,h 2008 Conference on precision electromagnetic measurements digest, pp. 700-701, 2008
Iida H., Y. Shimada and K. Komiyama [2009a], gNoise Temperature and Uncertainty Evaluation of a Cryogenic Noise Source by a Sliding Short Method,h IEEE Transactions on Instrumentation and Measurement, Vol. 58, No. 4, pp. 1090-1096, 2009
Iida H., Y. Shimada and K. Komiyama [2009b], gEvaluation of a cryogenic coaxial noise source based on the calibration method by single auxiliary transmission line,h 2010 Conference on precision electromagnetic measurements digest, pp. 743-744, 2009
Iida H., A. Widarta, T. Kawakami and K. Komiyama, gAttenuation Standard in the Frequency Range of 50-75 GHzh, IEEE Trans. Instrum. Meas (submitted)., Vol. 59, No. 11, pp. 2921-2929, 2010
Imae M., Y. Fujii, Y. Mitamoto1, T. Suzuyama, T. Kawakami, H. Yoshida, H. Hurukawa, and M. Susumu, gDevelopment of a GPS Common-view Terminal for Time and Frequency Remote Calibration Serviceh, Proc. of 2010 International Symposium on GPS/GNSS, 2010
Ishii M., and Y. Shimada [2009a], gReference Calibration Methods for Small Circular Loop Antenna in Low-Frequency Bandh, IEEE Trans. Instrum. and Meas., vol. 58, no. 4, pp. 1097-1103, 2009
Ishii M. and Y. Shimada [2009b], gA Near field 3-Antenna Method for Short Monopole Antennas in Low Frequency Bandsh, in Proc. IEEE Int. Symp. Electromagn. Compat. 2009, vol. Wed., pp. 324-327, 2009
Ishii M. and Y. Shimada, gA Reference Antenna Method for Non-resonant Electrically Short Monopole Antennash, in Proc. IEEE Int. Symp. Electromagn. Compat. 2010, vol. 1, pp. 56-61, 2010
Iwama T. A. Machizawa and H. Saito, gTime and Frequency Dissemination-System with Network (TFDN) Popular editionh, Asia-Pacific Radio Science Conference 2010, Toyama, Japan, 2010
Kajita M. [2008a], gProspects of detecting mp/me variance using vibrational transition frequencies of 2°-state moleculesh, Phys. Rev. A, vol. 77, pp. 012511 1-11, 2008
Kajita M. [2008b], gVariance Measurement of mp/me Using Cold Molecules h International Conference on Precision Physics of Simple Atomic System, 2008
Kajita M. [2009a], gSensitive measurement of mp/me variance using vibrational transition frequencies of cold moleculesh, New J. Phys., Vol. 11, pp. 055010 1-19, 2009
Kajita M and Y. Moriwaki [2009b], gDetection of variance in mp/me using vibrational transition frequency of CaH+ ionh, J. Phys. B, At. Mol. Opt. Phys., Vol 42, pp. 154022 1-6, 2009
Kajita M. [2009c], g Variance measurement of mp/me using cold moleculesh, Canadian Journal of Physics, vol. 87, pp. 743-748, 2009
Kajita M.[2009d], gDetection of variance in mp/me by the precise measurement of cold trapped moleculesh Cold Atoms and Molecules: Collisions, Field-Effects, and Applications
Kajita M. and Y. Moriwaki [2009e], gDetection of variance in mp/me using molecular vibrational transition frequenciesh, Colorado Cold Molecule Workshop, 2009
Kajita M., M. Abe and Y. Moriwaki[2010a], gProposed detection of the variance in mp/me via the vibrational transition frequencies of cold XH+ molecular ions (X = 40Ca, 24Mg, 64Zn, or 114Cd)h 22th International Conference on Atomic Physics, 2010
Kajita M., M. Abe, M. Hada, and Y. Moriwaki [2010b], hEstimated accuracies of pure XH+ (X :even isotopes of group II atoms) vibrational transition frequencies: Toward the test of the variance in mp/meh, J. Phys. B, At. Mol. Opt. Phys.,(submitted), 2010
Kaneko N., M. Maruyama, and C. Urano, gCurrent Status of Josephson Arbitrary Waveform Synthesis at NMIJ/AISTh, IEICE TRANS. ELECTRON. (submitted), 2010
Kawakami, T., A. Widarta, H. Iida and K. Komiyama, gVoltage ratio system constructed for RF attenuation standard -Working standard for control of attenuation calibrator-,h AIST Bulletin of Metrology, vol. 5, no.2, pp.111-123, 2006
Kinoshita M., K. Shimaoka and K. Komiyama [2008a], gRabi frequency measurement for microwave power standard using double resonance spectrumh, 2008 Conference on Precision Electromagnetic Measurements (CPEM), Digest, pp. 698-699, 2008
Kinoshita M, K. Shimaoka and K. Komiyama [2008b], gResearch on a new type of microwave power standardh, The papers of Technical Meeting on Instrumentation and Measurement, IEE Japan, IM-08-34 (in Japanese), 2008
Kinoshita M., K. Shimaoka and K. Komiyama [2008c], gDevelopment of a new microwave power standard using the Rabi frequencyh, Meeting Abstracts of the Physical Society of Japan, vol.63, issue 2, part 2, p.102 (in Japanese), 2008
Kinoshita M., K. Shimaoka and K. Komiyama [2009a], gDevelopment of a new microwave power standard using the Rabi frequency IIh, Meeting Abstracts of the Physical Society of Japan, vol.64, issue 1, part 2, p.169 (in Japanese), 2009
Kinoshita M., K. Shimaoka and K. Komiyama [2009b], gDetermination of microwave field strength using Rabi oscillation for a new microwave power standard,h IEEE Trans. Instr. Meas., volume 58, Issue 4, p. 1114-1119, 2009
Kinoshita M. [2009c], gStudy of a new microwave power standardh, AIST TODAY 2009-3 No.33, p.23, 2009
Kurokawa, S., M. Hirose, K. Komiyama,, gTime-domain Three Antenna Method for Evaluation of Antenna factors of Log-periodic Antennah, Proceedings of the 37th EuMC, pp.94-97.
Kinoshita M., K. Shimaoka, and K. Komiyama [2009d], gA study of a microwave power standard based on the Rabi oscillationh, Meeting Abstracts of the Physical Society of Japan, vol.64, issue 2, part 2, p.106 (in Japanese), 2009
Kinoshita M., K. Shimaoka, K. Komiyama [2010a], gAbsolute measurement of microwave power based on the atomic Rabi frequencyh, Conference on Precision Electromagnetic Measurements (CPEM) 2010 Digest, pp. 734-735, 2010
Kinoshita M., K. Shimaoka, and K. Komiyama [2010b], gUncertainty of Atomic Microwave Power Standardh, Asia-Pacific Radio Science Conference 2010, Proceedings, AB-6, 2010
Kinoshita M., K. Shimaoka, and K. Komiyama [2010c], gAtomic microwave power standard based on the Rabi frequencyh, IEEE Trans. on Instrum. Meas. (submitted), 2010.
Kohmura, A and T. Iwasaki gDetermination of Magnetic Complex Antenna Factor of Double-Output Shielded Loop Antenna Using an Equivalent Circuith, IEEJ, Trans. Fundamentals and Materials, Vol. 126, No. 6, pp. 414-419, 2006
Kohno, T., M. Yasuda, K. Hosaka, H. Inaba, Y. Nakajima, and F.-L. Hong, gOne-Dimensional Optical Lattice Clock with a Fermionic 171Yb Isotopeh, Appl. Phys. Express., Vol. 2, pp. 072501 1-3., 2009
Kon S., T. Yamada, and T. Tadokoro, gVerification and Uncertainty Evaluation of an AC Shunt Calibration System at Power Frequenciesh, Conference digest CPEM2010, pp.343-344, June 2010
Kumagai, M., H. Ito, M. Kajita, and M. Hosokawa [2008a], gEvaluation of caesium atomic fountain NICT-CsF1h, Metrologia, vol. 45, pp139-148., 2008
Kumagai, M., H. Ito, M. Kajita and M. Hosokawa [2008b], gCurrent Status of NICT atomic fountainsh, Asia-Pacific Time and Frequency Forum 2008 vol.44, no.1A, pp.229-230.
Kumagai M., M. Fujieba, T. Goto and M. Hosokawa [2008c], gDevelopment of frequency transfer via optical fiber link at NICTh, 40th Annual Precise Time and Interval (PTTI), 2008
Kumagai M., M. Fujieda, S. Nagano and M. Hosokawa, gStable radio frequency transfer in 114 km urban optical fiber linkh, Opt. Lett., vol. 34, no. 19, pp. 2949-2951, 2009
Kurokawa S., M. Hirose and K. Komiyama , gMeasurement and Uncertainty Analysis of Free-Space Antenna Factors of a Log-Periodic Antenna Using Time-Domain Techniquesh, IEEE Trans. Instrum. Meas., vol. 58, no.4, pp.1120-1125, 2009.
Kurokawa S., M. Ameya, and M. Hirose [2010a], gTime-domain Three Antenna Method for Bi-conical Antennah, in CPEM2010 Dig., pp.359-360, Daejeon, Korea, June 2010
Li Y., S. Nagano, K. Matsubara, H. Ito, M. Kajita, and M. Hosokawa [2008a], hNarrow-Line and Frequency Tunable Diode Laser System for S-D Transition of Cat+ Ionsh, Jpn. J. Appl. Phys. Vol. 47, pp.6327-6332, 2008
Li Y., K. Matsubara, S. Nagano, H. Ito, M. Kajita, Y. Koyama, and M. Hosokawa [2010a] gA clock laser with high frequency stability and highly precise transferh, 24th European Frequency and Time Forum, 2010
Machizawa A., T. Iwama H. Saito, T. Gotoh, H. Toriyama and M. Hosokawa, gNational Time and Frequency Standard Dissemination System in ICT Era,h Asia-Pasific Workshop on Time and Frequency, 2008
Maruyama M., C. Urano, N. Kaneko, H. Yamamori, A. Shoji, M. Maezawa, Y. Hashimoto, H. Suzuki, S. Nagasawa, T. Satoh, M. Hidaka, and S. Kiryu, gUtilization of a Cryo-Prober System for Operation of a Pulse-Driven Josephson Junction Arrayh, Proc. 9th European Conference on Applied Superconductivity (EUCAS f09), Dresden, P-282, 2009
Maruyama M., T. Yamada, H. Sasaki, H. Yamamori, C. Urano, and N. Kaneko, gGeneration of AC Waveforms Using a NbN-Based Programmable Josephson Voltage Standard System with a 10-K Coolerh, Proc. 27th Conf. Precision Electromagnetic Meas. (CPEM 2010), Daejeon, Korea, MoA1-3, June 2010
Matsubara K., K. Hayasaka, Y. Li, H. Ito, S. Nagano, M. Kajita and M. Hosokawa [2008a] gFrequency Measurement of the Optical Clock Transition of 40Ca+ Ions with an Uncertainty of 10-14 Levelh, Appl. Phys. Exp., Vol. 1, pp. 067011-06013, 2008
Matsubara K., Y. Li, H. Ito, S. Nagano, K. Hayasaka and M. Hosokawa [2008b], hAbsolute Frequency Measurement of the 4 2S1/2-3 2D5/2 Quadrupole Transition in 40Ca+ Ionsh, International Union of Radio Science 2008 General Assembly (URSI2008GA), 2008
Matsubara K., Y. Li, H. Ito, S. Nagano, M. Kajita, R. Kojima, K. Hayasaka and M. Hosokawa [2008c], gAbsolute Frequency Measurement of the 40Ca+ Clock Transition at the 10-14 Levelh Asia-Pacific Workshop on Time and Frequency, 2008
Matsubara K., Y. Li, S. Nagano, H. Ito, M. Kajita, R. Kojima, K. Hayasaka, Y. Hanado and M. Hosokawa [2009a], gAbsolute Frequency Measurement of the 40Ca+ Clock Transition using a LD-Based Clock Laser and UTC(NICT)h, 2009 European Frequency & Time Forum & IEEE Int'l Frequency Control Symposium, 2009
Matsubara K., Y. Li, S. Nagano, H. Ito, M. Kajita, R. Kojima, K. Hayasaka, M. Hosokawa and Y. Hanado [2009b] gFrequency measurement of the 40Ca+ clock transition using a LD-based clock laser and UTC(NICT)h, SPIE Symposium on SPIE Optical Engineering + Applications, 2009
Morioka T. [2009a], gUncertainty of free space dipole antenna factor from 1 GHz to 2 GHzh, IEEE Trans. Instrum. Meas., vol. 58, no. 4, pp. 1135-1140, Apr. 2009
Morioka T. [2009b], gElectromagnetic field measurement using circular wire scatterers,h in Proc. IEEE Int. Symp. Electromagn. Compat., pp. 314-318, Austin, Tx., USA, Aug. 2009
Morioka, T.[2010a], gProbe response to a non-uniform E-field in a TEM cellh, in CPEM Dig., pp. 327-328, Daejeon, Korea, June 2010
Morioka, T. and K. Hirasawa [2010b], gMoM calculation of the properly defined dipole antenna factor with measured balun characteristicsh, IEEE Trans. on Electromagn. Compat. (submitted), 2010
WMurayama, Y., C. Urano, A. Iwasa, H. Yamamori, A. Shoji and M. shizaki, gComparison between a 1-V NbN-based Programmable and a Conventional SIS Josephson Arrayh, Jpn. J. Appl. Phys., vol. 46, no. 12, pp. 7912-7915, 2007
Nagano S., H. Ito, Y. Li, K. Matsubara and M. Hosokawa [2009a], gStable Operation of Femtosecond Laser Frequency Combs with Uncertainty at the 10-17 Level toward Optical Frequency Standardsh, Jpn. J. Appl. Phys., Vol. 48, pp. 42301, 2009
Nakajima Y., H. Inaba, K. Hosaka, K. Minoshima, A. Onae, M. Yasuda, T. Kohno, S. Kawato, T. Kobayashi, T. Katsuyama and Hong F.-L., gA multi-branch, fiber-based frequency comb with millihertz-level relative linewidths using an intra-cavity electro-optic modulatorh, Optics Express, vol. 18, No. 2 1667-1676, 2010
Nakamura Y. and A. Domae, gNational electrical standards supporting international competition of Japanese manufacturing industries Synthesiologyh, Vol.3, No.3, p.213-222, 2010
Oe T., N. Kaneko, C. Urano, T. Itatani, H. Ishii and S. Kiryu, gDevelopment of Quantum Hall Array Resistance Standards at NMIJh, CPEM 2008 Digest, p.20, June 2008
Oe T., K. Matsuhiro, C. Urano, H. Fujino, H. Ishii, T. Itatani, G. Sucheta, M. Maezawa, S. Kiryu and N. Kaneko [2010a], gDevelopment of 10 k¶ Quantum Hall Array Resistance Standards at NMIJh, CPEM 2010 Digest, p.619, June 2010
Oe T., K. Matsuhiro, A. Domae, C. Urano, H. Fujino, H. Ishii, T. Itatani, G. Sucheta, M. Maezawa, S. Kiryu and N. Kaneko [2010b], gDevelopment of On-Chip Double-Shielded Quantum Hall Device for Use in AC Quantized Hall Resistance Measurementh, CPEM 2010 Digest, p.376, June 2010
Sakamoto N. and Y. Nakamura [2010b], gCalibration Method for Large Capacitances Using a Current Comparator with an Inductive Voltage Dividerh, CPEM2010 Digest, pp.412-413
Sakamoto Y., N. Kaneko, T. Oe, M. Kumagai, M. Zama , gNovel 100 ¶ metal foil DC resistorh, CPEM 2010 Digest, pp615 - 616, June 2010
Sasaki H., H. Yammori, T. Yamada, H. Fujiki, A. Shoji, I. Budovsky and K. Shimizume, gEvaluation of Low-Frequency Characteristic of a Thermal Converter Using Programmable Josephson Voltage Standardh, IEEE Trans. Instrum. Meas. (submitted), 2010
Shimada, Y., gUncertainty analysis of radio-frequency noise standardh, AIST Bulletin of Metrology, vol.5, no.2, pp.105-110, 2006
Takahashi Y., F. Nakagawa, H. Kunimori, J. Amagai, S. Tsuchiya, R. Tabuchi, S. Hama and H. Noda, gFirst Experiment of Precise Time Transfer using ETS-VIII Satelliteh, CPEM2008, 2008
Takamizawa A., S. Yanagimachi, Y. Shirakawa, K. Watabe, K. Hagimoto, and T. Ikegami, gCesium Atomic Fountain Clocks at NMIJh, Proc. 42nd Annual Precise Time and Time Interval (PTTI) Meeting, pp.321-328, 2010
Takamizawa A., Y. Shirawaka, S. Yanagimachi and T. Ikegami, gProposal of a truncated atomic beam fountain for reduction of collisional frequency shifth, Phys.Rev. A 82, 013632, 2010
Takamoto M., H. Katori, S. I. Marmo, V. D. Ovsiannikov and V. G. Pal'chikov, gProspects for optical clocks with a blue-detuned latticeh, Phys. Rev. Lett., Vol. 102, pp. 063002, 2009
Urano C., M. Maruyama, N. Kaneko, H. Yamamori, A. Shoji, M. Maezawa, Y. Hashimoto, H. Suzuki, S. Nagasawa, T. Satoh, M. Hidaka, and S. Kiryu [2009a], gOperation of a Josephson Arbitrary Waveform Synthesizer with Optical Data Inputh, Supercond. Sci. Technol., Vol. 22, 114012 (4pp), 2009
Urano C., M. Maruyama, N. Kaneko, H. Yamamori, A. Shoji, M. Maezawa, Y. Hashimoto, H. Suzuki, S. Nagasawa, T. Satoh, M. Hidaka, and S. Kiryu [2009b], gJosephson Arbitrary Waveform Synthesizer Using Opto-Electronicsh, Proc. 9th European Conference on Applied Superconductivity (EUCAS f09), Dresden, P-533, 2009
Widarta, A and T. Kawakami [2008a], gA Simple Measurement Technique for Precision RF Attenuationh, 2008 Conference on Precision Electromagnetic Measurements Digests, pp. 432- 433, 2008
Widarta, A. [2008b], gSimple and Accurate Radio Frequency Attenuation Measurements using General-Purpose Receiverh, The International Conference on Electrical Engineering 2008, O-063, 2008
Widarta, A. and T. Kawakami [2009a], gA Simple RF Attenuation Measurement Technique with Small Mismatch Uncertaintyh, IEEE Trans. Instrum. Meas., vol. IM-58, no. 4, pp. 1164-1169, April 2009.
Widarta, A. and T. Kawakami, gMismatch Correction in RF Attenuation Measurement Using Precision Airlinesh, CPEM Dig., Broomfield, CO, Jun. 8-13, 2008, pp.432-433, 2010
Yamada T., S. Kon and N. Sakamoto, gEvaluations of a Wideband Inductive Voltage Divider and Non-sinusoidal Power Measurement Systemh, 2010 CPEM digest, pp.239-240, 2010
Yamaguchi A., N. Shiga, S. Nagano, H. Ishijima, M. Hosokawa and T. Ido [2010a], gOptical Lattice Clockh, 22nd International conference on Atomic Physics, 2010
Yanagimachi S., A. Takamizawa, Y. Yoshida, A. Yanagimachi, K. Watabe, K. Hagimoto and T. Ikegami, gRecent progress of an atomic fountain frequency standard NMIJ-F1 (2006-2007)h, 2008 CPEM Digest, Broomfield, pp.324-325, 2008
Yasuda, M., T. Kohno, H. Inaba, Y. Nakajima, K. Hosaka, A. Onae, and F.-L. Hong, gFiber-comb-stabilized light source at 556 nm for magneto-optical trapping of ytterbiumh, J. Opt. Soc. Am. B, Vol. 7, pp. 1388-1393, 2010