COMMISSION A : Electromagnetic Metrology(November 2010 - October 2013)
Edited by Mitsuru Musha (University of Electro-communications) and Yasuhiro Koyama(National Institute of Information and Communications Technology)

A1. Time and Frequency Standards and Time Transfer Technique
The researches and developments on Time and Frequency Standards and Time transfer inJapan are mainly carried out in National Institute of Information Technology (NICT) andNational Metrology Institute of Japan (NMIJ).
In NICT, Kumagai et al. are going to upgrade NICT-CsF1 aiming the operation at the 10-16level (currently operating with 1.4 x 10-15). They are developing also the 2nd fountain(NICT-CsF2), with which a frequency stability of 3 x 10-13 /1/2 was obtained. They completed
evaluations of most systematic frequency shifts and their uncertainties for CsF2 at the level below
5 x 10-16.
A microwave frequency standard using the 171Yb+ is under development at NICT. For thispurpose, Shiga et al. constructed an experimental apparatus and the absolute frequency of the171

Yb+ hyperfine transition was measured with 4 x 10-14 uncertainty.

This apparatus is used todemonstrate a new measurement method using atomic phase lock.
The time difference between UTC (NICT) and UTC has been kept almost within +25 ns to-19 ns for the last 3 years. NICT has 29 Cs clocks and 7 H-masers. UTC (NICT) is generated byusing 18 high-performance Cs clocks and 3 H-masers. Other Cs clocks are in operation at two
LF stations and at Advanced ICT Research Institute of NICT. UTC (NICT) has been used as thereference for frequency calibration services.
NICT was certified to be in accordance with the ISO/IEC 17025 for the frequency calibration
system from National Institute of Technology and Evaluation (NITE) in March 2001. NITE
provided an accreditation of ISO/IEC 17025 to NICT on 31 January 2003, and also provided anaccreditation of ISO/IEC 17025 of the frequency remote calibration system and the time scaledifference to NICT on 2 May 2006 and on 30 September 2011 respectively. BMC of carried insystem was changed to 5 x 10-14 in April 2007. The measurement range of frequency calibration
was expanded from 1 Hz to 100 MHz in September 2011. NICT received surveillance by NITE
in February and renewed IAJapan certificate dated April 26, 2013 from NITE.
Fujieda et al. [Fujieda et.al., 2011] developed an all-optical link system for making remote1comparisons of two distant ultra-stable optical clocks. An optical carrier transfer system basedon a fiber interferometer was employed to compensate the phase noise accumulated during the
propagation through a fiber link. Transfer stabilities of 2 × 10-15 at 1 s and 4 × 10-18 at 1 s wereachieved in a 90-km link.
NICT has performed various experiments using Two-Way Satellite Time and Frequency
Transfer (TWSTFT). Gotoh et al. [Gotoh et.al., 2011] have developed a new two-way timetransfer modem to improve the time transfer precision of remote clock comparison. For the
real-time digital signal processing stages implemented in software, they relied on a graphics
processing unit (GPU) and performed two-way satellite time transfer experiments using thesemodems between Japan and Taiwan. The obtained results are consistent within 200 ps withrespect to the results of GPS carrier phase time transfer. The first international TWSTFT
experiment using a new software-defined modem with dual pseudo-random noise (DPN) codes
were performed over a period of 6 months [Wen-Hung et al., 2012]. The results of DPN exhibit
excellent performance, which is competitive with the GPS precise point positioning (PPP)
technique in the short-term and consistent with the conventional TWSTFT. Time deviations ofless than 75 ps are achieved for averaging times from 1 s to 1 d. Fujieda et al. [Fujieda et.al.,2012] started to implement a carrier-phase information to improve the short-term stability of
TWSTFT. The experiments in a domestic short baseline were performed. The short-term
stability of 4 × 10-13 at 1 s was achieved.
NICT also performed direct time comparisons using the first Quasi-Zenith Satellite (QZS-1)
in order to monitor the onboard clock as a part of the satellite navigation system [Nakamura etal., 2013]. The NICT system achieves a measurement precision of about 25 ps which is an orderof magnitude better than the precision of the clock parameters obtained from the combined orbit
and clock estimation.
A study via VLBI simulation for evaluating the potential of the time and frequency transfer
was performed by assuming use of the next-generation VLBI technique, which is the “VGOS(VLBI2010 Global Observing System)” including the wide-band receiver and data acquisition
system, small antenna, antenna slew speed improvement, and phase delay measurement. This
simulation indicated that feasibility of the frequency stability with the VLBI measurement
would be at the order of 10-16 at one-day interval [Hobiger 2011 a,b]. Further feasibility study
campaign experiment was performed by using 11-m antennas between Kashima-Koganei (100km distance) on 19-23 Feb. 2012. Clock difference between two hydrogen masers at each site
was compared with multi techniques: GPS, VLBI, and TWSTFT (code). It is notable that the2increase of VLBI observation bandwidth from 500 MHz to 1 GHz improved the precision ofclock comparison. This result encourages developing new wideband VLBI system [Sekido,
2012 a,b, 2013 a,b, Koyama, 2012, 2013, Takefuji, 2012 a,b,c, 2013].
The development of the new wideband VLBI system for T&F transfer named 'Gala-V' has
started since 2012 [Ichikawa, 2011, Kondo, 2012]. The system is designed in composition oftransportable small diameter antenna pair and large diameter antenna. And its observation
frequency range was selected so that coincides with that of the next generation international
geodetic VLBI system (VGOS) for future joint observation with international VLBI stations[Ujihara, 2011, 2012 a,b]. Wide frequency (6.4 GHz – 15 GHz) feed for cassegrain 34-m
diameter antenna was originally designed and installed to Kashima 34-m radio telescope in
2013. Test evaluation experiment with the Gala-V system is being planned in 2014.
In NMIJ, following researches have been conducted.
Primary frequency standards at NMIJ: NMIJ has made the calibration of the International
Atomic Time (TAI) 4 times between November 2010 and March 2011 with the Cs atomic
fountain frequency standard, NMIJ-F1 with a combined uncertainty of 3.9×10-15 [Circular T,
Takamizawa et al., 2010, Takamizawa et al., 2012]. However, the resonance frequencies of the
microwave cavities were shifted out of the atomic resonance due to the huge earthquake.
Moreover, the cesium source was exhausted. Therefore, we opened the vacuum chamber toreplace the microwave cavities and supply a new cesium ampule. Here, the microwave cavities
are parts of the vacuum chamber in the new version. Then, the ultrahigh vacuum has beenobtained. Now we are making the optical setup again. In parallel, our second fountain NMIJ-F2
has been developed, aiming uncertainty of < 1×10-15 as an immediate goal [Takamizawa et al.,2010, Takamizawa et al., 2012, Takamizawa et al., 2013]. In addition, the large frequency
corrections for the 2nd–order Zeeman shift, the blackbody radiation shift, and the collisional
shift have been evaluated. Therefore, we are now in a position to compare NMIJ-F2 with TAI
and the other primary frequency standards at the 1×10-15 level. Ultra-stable microwave
oscillator: One of the two CSOs was modified with the addition of a low-vibration pulse-tube
cryocooler to be employed as a local oscillator for the fountains. No liquid helium refills areneeded for the cryocooled version of the CSOs. Phase noise standards: We have developed aphase noise standard [Watabe et al., 2012, Yanagimachi et al., 2013a, Yanagimachi et al., 2013b,
Yanagimachi et al., 2013c].
Time Keeping at NMIJ: All atomic clocks ran down due to power failure by the Great East
Japan Earthquake in 2011. Since then NMIJ has been trying to recover the damaged equipment.

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At present four active hydrogen maser frequency standards and two cesium atomic clocks withhigh-performance beam tubes (Agilent 5071A) are operated for time keeping. Those atomic
clocks are kept in individual chambers, whose temperatures are kept to within 0.2 deg C. One of
the hydrogen masers is used as a source oscillator for the generation of UTC (NMIJ) to improve
the short-term stability. UTC (NMIJ) is created by frequency-steering the hydrogen maser
output signal to UTC using a frequency stepper. Time and Frequency Transfer: In NMIJ, dual
frequency carrier phase GPS receiver is one of the main international time and frequency
transfer tools.
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 systemusing Wavelength Division Multiplexing technology is studied as one of future precise time andfrequency comparison systems. In addition, NMIJ started the research on a precise frequency
comparison system using an optical carrier..
Frequency Calibration Service at NMIJ; NMIJ has been providing the remote frequency
calibration service using the GPS common-view method and Internet since 2006. The CMCs of
the service are 1.1×10-13 (baseline: 50 km), 1.4×10-13 (baseline: 500 km) and 4.9×10-13 (baseline:
1,600 km) at an averaging time of one day. The number of users is 16 in 2014; it is on the riseyear by year.

A2. Laser Stabilization and Frequency Measurement
The researches and developments on laser stabilization and frequency measurement in Japanare mainly carried out National Institute of Information Technology (NICT), National
Metrology Institute of Japan (NMIJ) and RIKEN group.
In NICT, optical frequency standard using Sr atom and Ca+ ion have been developed.
Yamaguchi et al. developed the frequency standard based on the 87Sr 1S0-3P0 transition frequency,
using atoms in an optical lattice [Yamaguchi, 2012]. Matsubara et al. reduced the uncertainty of
the absolute frequency of 40Ca+ 2S1/2-2D5/2 transition down to 3 x 10-15, and the ratio of the 40Ca+
and Sr transition frequencies with the uncertainty of 2 x 10-15 [Matsubara, 2012]. A new opticalfrequency standard based on the 115In+ 1S0-3P0 transition frequency is under development to ahigher accuracy than that of 40Ca+. For this purpose, techniques for generating ion chainsconsisting of 115In+ and 40Ca+ have been developed [Hayasaka, 2012].
A new frequency standard in THz (0.1-10 THz, wavelength 30 m - 3 mm) domain has
started in NICT. Ito et al. developed a THz frequency comb for the absolute THz frequency

4

measurements. Its measurement accuracy has attained to 10-17 level around 0.3 THz [Ito, 2013].
Nagano et al. demonstrate microwave synthesis from a continuous-wave THz oscillator[Nagano, 2013]
Also some proposals for new frequency standards in the THz and Infrared area were given in
NICT. Kajita et al. proposed the precise measurement of the vibrational transition frequencies ofalkali earth - H+ molecular ions eliminating the Stark shift induced by probe lasers. [Kajita et al.,2011 a, 2012 b]. They proposed also to measure the vibrational transition frequencies of alkali
earth-alkali diatomic molecules trapped in an optical lattice [Kajita et al., 2011b, 2012 a, 2013].
NMIJ has developed an Yb optical lattice clock. In 2012, they demonstrated an improved
frequency measurement of the 1S0 – 3P0 clock transition in 171Yb bound in the Stark-shift-free
optical lattices with an uncertainty of 3.9×10-15 that is limited by UTC-NMIJ [Yasuda et al.,2012]. Consequently, the clock transition in Yb was selected as one of secondary
representations of the second by the International Committee for Weights and Measures (CIPM).
In order to evaluate the optical clocks that exceed the performance of the Cs fountain primary
standards, one needs to measure the frequency ratio between optical clock transitions in the
different types of the optical clocks. Therefore, at NMIJ, Sr optical lattice clock has also beendeveloped and, furthermore, an Yb/Sr dual optical lattice clock project is now underway.
At NMIJ, optical frequency combs play an important role in their optical clock project. In theclock laser system, the highly stabilized fibre comb is able to transfer the linewidth andfrequency stability from one laser frequency to another and it plays a role of an ultra-stable local
oscillator for multi wavelengths. Using the linewidth transfer technique with high-speed
controllable fibre-based frequency combs, cooling laser operated at 689 nm for Sr and clock
lasers operated at 578 nm and 698 nm for Yb and Sr, respectively, are stabilised andsuccessfully used for atomic spectroscopy [Akamatsu et al., 2012, Iwakuni et al., 2012, Inaba etal., 2013].
In order to reduce the effect of the thermal noise on the optical cavity that could givefrequency stability limits for short averaging times, a long cavity would be one of attractive
solutions. For the long cavity, a new spacer material with high specific rigidity would be
required, because a long cavity would be sensitive to the seismic noise in laboratories. At NMIJ,
they have developed an optical cavity with an ultralow expansion ceramic spacer andinvestigated the thermal properties of the ceramic [Hosaka et al., 2013].
Katori group at the University of Tokyo and RIKEN has been developing optical latticeclocks with Sr Hg atoms, and optical frequency transfer system using a telecom fiber link5

between these two sites.
In 2011, the University of Tokyo developed a scheme to compare two clocks with highstability by canceling out the laser noise. They succeeded to compare two clocks with the Allan
deviation of σ

4

10

⁄√

and reached 1

10with an averaging timeof2,000 s, which corresponds to the quantum projection noise limit of optical lattice clocks with1,000 atoms [Takamoto et al., 2011].
Frequency comparison between two remote Sr optical lattice clocks operated in the
University of Tokyo and NICT was performed via a phase-stabilized optical fiber link
[Yamaguchi et al., 2011]. The frequency comparison of two remote clocks with their distance of
24 km measures the relative frequency difference to be
gravitational red shift of

1.0

7.3

10

and the2.6 Hz due to the height difference of 56 m.

Prof. Katori with theorists [Ovsiannikov et al., 2013] discussed the multipolar andhigher-order light shift for Sr atoms.
RIKEN has developed two cryogenic strontium (Sr) lattice clocks since 2011. Thus far, theaccuracy of Sr lattice clocks has been limited by the uncertainty of ambient blackbody radiation
shift. By installing a cryogenic chamber, they have succeeded to suppress the blackbody
radiation and compare two cryogenic Sr lattice clocks with the uncertainty of 10-18 level[Ushijima et al., to be published].
Frequency transfer system between RIKEN and the University of Tokyo has been developed
to compare remote cryogenic Sr lattice clocks at the uncertainty of 10
be published]. The link stability is evaluated to be 1

10

[Akatsuka et al., toat 1 s and reaches 1

10at

100 s, which corresponds to the gravitational red shift for the height difference of 1 cm.
RIKEN is also developing a lattice clock with mercury (Hg) atoms. Hg atoms have one orderof magnitude smaller sensitivity to the blackbody radiation than Sr and Yb atoms. This enables
the accuracy at 10-18 even in a room temperature environment. They have succeeded in trapping
Hg atoms in a magic optical lattice and precise spectroscopy of Hg clock transition, and started
frequency comparison between Hg and Sr lattice clocks.
Sugiyama group at Kyoto University is developing single Yb+ ion clocks. They succeeded insingle-ion spectroscopy of the 2S1/2－2D5/2 transition in 174Yb with a spectral width of 5 kHz[Imai et al., 2013]. They also study laser frequency stabilization to 6S－8S two-photontransitions in Cs in a gas cell in order to pursue high frequency-stability. They obtained a root
Allan variance of 4.4 x 10-14 at an averaging time of 16 s [Uehara et al., 2012].

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A3. Realization of Electrical Unit (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 the Electricity and Magnetism (EM) Division of National Metrology
Institute of Japan (NMIJ), partly in collaboration with several other institutes in the Advanced
Industrial Science and Technology (AIST). The EM division has two sections, the Applied
Electrical Standards Section and the Quantum Electrical Standards Section. The Applied
Electrical Standards Section takes charge of the AC/DC transfer, the low value impedance andthe power standards. The Quantum Electrical Standards Section covers the Josephson voltage,
the quantum Hall resistance, and the high value impedance standards.
NMIJ has been studying a quantum-based Johnson noise thermometry in quest ofworld-record electronic measurement of Boltzmann’s constant and absolute temperature
measurement in collaboration with the Thermometry Section of NMIJ and the NIST (Boulder
and Gaithersburg). A Josephson-junction chip dedicated for JNT and other components required
for JNT measurement such as data acquisition system have been developed. Up to now, wehave succeeded in measuring cross power spectra of a 100 ohm resistor at triple point of watertemperature and a reference signal generated with the quantum voltage noise source (QVNS).
We found, however, that there is some error in the cross spectra data obtained in our present
system. We are now trying to improve our system and suppress the error [Urano et al., 2012].
A programmable Josephson voltage standard (PJVS) system has been optimized for AC
waveform synthesis and adopted for sampling measurement using a calibrator and a thermal
converter. Low-frequency characteristics of a thermal converter at below 10 Hz have beensuccessfully evaluated using the sampling measurement. We are now trying to increase thevoltage level from 3 Vrms to 10 Vrms, replacing the PJVS chip, in collaboration with CMS(Taiwan). Development of a calibration system for Zener voltage standards using aliquid-helium-free PJVS has been finalized. The system has being checked through direct andindirect comparisons with our conventional JVS (CJVS) system. A bilateral comparison of
PJVS systems in NMIJ (Japan) and CMS (Taiwan) (APMP.EM.BIPM-K11.5) is now inprogress with a support by KRISS (Korea). Another experiment for evaluating the linearity
characteristics of commercial digital volt meters (DVMs) has been started using the system.
Development of a high-stable and user-friendly DC voltage generator based on a rack-mountPJVS system with a small cryocooler is also in progress in the collaboration with the
Nanoelectronics Research Institute (NeRI), AIST [Kaneko et al., 2011, 2012a, Amagai et al.,7

2013,].
A compact and ultra-stable 100 Ω standard resistor is finished its development anddevelopment of resistors (1 Ω to 10 kΩ) with other decade values are in progress. This 100 Ω
standard resistor of which temperature coefficients is extremely low, less than 0.1 ppm/K at room
temperature, and resistance values are greatly stable, less than 0.1 ppm/year have beensuccessfully manufactured and in market. The pressure coefficients are typically less than +0.01(μΩ/Ω)/(-250 hPa) and the humidity coefficients of those resistors are immeasurable level[Kanko et al., 2012b, 2012c]. Current coefficients are lower than measurement limit as well
[Domae et al., 2013a]. Trilateral comparison of four Alpha Electronics 100 Ω using QHR and
CCC was carried out with KRISS (Korea) and NIST (USA). The calibrated values have been
agreed within a few parts in 10-8 at a rough estimate.
By using the fabrication technology of highly stable 100-Ω metal-foil resistor component,
developed in collaboration between the NMIJ and Alpha Electronics Corp., 100-Ω standard
resistors with a four-terminal-pair design, which enables ac measurements, have been fabricated.
For the AC characteristics, the frequency dependence of the resistance and phase angle has been
evaluated [Domae et al., 2012a, 2013a].
Conventional single Hall bar QHR devices have been fabricated and several devices have been
provided for several NMIs.
Newly designed 10 kΩ quantum Hall array resistance standard devices also have been
fabricated. This device consists of 16 Hall bars, and its nominal value has only 0.0342 ppm
difference based on RK-90 from the integer value of 104. We observed a clear 10 kΩ plateau, andthe measured value agreed with its nominal value within a few ppb [Oe et al., 2011, 2013].
Test devices of ac-QHR with on-chip double-shielding have been fabricated at NMIJ and theirac-characteristic was evaluated at PTB [Kaneko et al., 2012e, 2013a].
A resistive voltage divider, which is constructed from a binary-segmented series array of QHRbars fabricated on one chip, named the 'QHR voltage divider', has been developed. From thepreliminary tests, the results of the Hall resistance measurement showed large and well-definedplateaus, deviations from nominal voltage ratios were measured to be less than 1.4 × 10−6, andthe expanded uncertainty of the voltage ratio measurement was estimated to be less than 4.1 ×
10−6 [Domae et al., 2012b, 2012c].
One researcher of NMIJ had stayed at the NIST Gaithersburg for collaboration work ongraphene. Shubnikov–de Haas (SdH) oscillation was observed in graphene synthesized on the
Si-terminated surface of SiC. Carrier density in SiC graphene was successfully controlled with8

photochemical gating and QHE plateau (i=2) was observed. And QHE plateau was observed ingraphene which made at the NIST Boulder with CVD technique and fabricated at Gaithersburg[Shimamoto et al., 2012, 2013].
The SINIS (Super/Insulator/Normal/Insulator/Super) turnstile devices for a single electron
pumping have been fabricated. This device consists of a single pumping device and 14 parallel
pumping devices. A measurement system has been also developed in a dilution refrigerator. At
present, we succeeded to pump the current of 160pA (100 MHz) with the standard deviation of 1
part in 104. Also to achieve metrological requirements, the influence of environments such astemperature, magnetic fields are studied. We also study different type of device, such as atunable barrier-pumping device and small Josephson junction device [Kaneko, 2012d, 2013b].
In order to maintain high reliability of the capacitance standard, NMIJ has been performing
long-term monitoring of standard capacitors and of capacitance differences among a number ofstandard capacitors. After the massive earthquake on March 11, 2011, validation of calibrationand measurement capabilities (CMCs) of the capacitance standard based on the analysis of thesemonitoring results was conducted [Domae et al., 2013b].
We have developed a capacitance-scaling bridge using a current comparator and an inductive
voltage divider for calibrating 4TP-defined capacitance standards of 100 μF. The expanded
uncertainties of the capacitance and the dissipation factor of 100 μF at 120 Hz are 11 μF/F and 14
μrad, respectively. The bridge was recently modified aiming to calibrate the standards of 1 mF.
The expanded uncertainties of the capacitance and the dissipation factor of 1 mF at 120 Hz are
260 μF/F and 270 μrad, respectively [Sakamoto et al., 2010].
NMIJ has started a development of precision measuring techniques for diagnosis of the energy
storage devices such as lithium-ion batteries (LIBs) and super-capacitors by using an impedance
spectroscopy method. We have a plan to establish a metrology for evaluating the storage powerdevices. We have developed the impedance spectrum measurement system which is suitable fortesting LIB cells using a frequency response analyzer and a potentio-/galvanostat.
NMIJ has provided ac-dc voltage difference transfer calibration of thermal converters in thevoltage range from 10 mV to 1000 V and in the frequency range from 10 Hz to 1 MHz. A
comparison system for ac-dc current difference transfer standards up to 5 A has been developed.
Practical thin film multi-junction thermal converters (MJTC) have been developed at
NMIJ/AIST in collaboration with NIKKOHM Co. Ltd. A high-current thin-film multijunction
thermal converter up to 200 mA for AC-DC current transfer standards has been developed [Fujiki
et al., 2013].

9

A differential sampling measurement system using a 3 V RMS AC-programmable Josephson
voltage standard (AC-PJVS) system has been developed, and AC-DC transfer differences ofthermal voltage converters have been successfully characterized down to 1 Hz [Amagai et al.,2013]. To expand the voltage range from 3 V to 10 V for this technique, we are now developing a
differential sampling system using a 10 V RMS AC-PJVS system, in collaboration through the
Nanoelectronics Research Institute (NeRI). The low-frequency property of a single-junction
thermal converter down to 1 Hz has been successfully simulated using an improved
electro-thermal model [Amagai et al., 2012a, b, c]. The long-term stability of our thin-film
multijunction thermal converter has been improved by fabricating a new thermopile pattern. To
further improve the sensitivity and low-frequency property, the thin-film multijunction thermal
converter have been characterized under vacuum conditions, in collaboration with NIKKOHM Co.
Ltd [Amagai et al., 2012]. The study on absolute measurements of Seebeck coefficient using an
AC-DC measurement technique has started. With regard to a calibration service, we haveprovided a calibration service of AC voltmeters using a thermal converter in the frequency range
from 4 Hz to 10Hz, 40 Hz to 100 kHz at the RMS voltage of 1V and10 V.
NMIJ had developed a calibration system for non-sinusoidal voltage, current and power sources
at 100V/5A of fundamental wave and at 10 V/ 3 A of higher harmonics in 2011. The extension of
the range of the system is delayed because of the temporary transfer of the person in charge[Yamada et al., 2012a].
Also, we developed an ac shunt calibration system at 5 amperes and 50 – 60 Hz. The system
has been expanding up to 1 kHz at this moment. NMIJ has some plans for expanding up to 100
amperes and 10 kHz by 2015 according to requests from the industries which need power
calibration and antenna calibration. To realize the expansion, the NMIJ ac current ratio standard
has been re-checked and its calibration frequency has been expanded up to 4 kHz by improvementof its uncertainty estimation [Kon et al., 2011, 2012a, 2013c]. In addition, the application systemsof power measurement using shunt and IVD standards have been developed [Kon et al., 2012b,
2013a, 2013b, 2013d].
Using the NMIJ standards of shunt and current transformer, an evaluation system for electronic
current transformers (ECTs) accompanied by merging units (MUs) in accordance with IEC 61850
and IEC 60044-8 for automated substations has been developed. The system allows long-term
evaluation of the ECT/MU of 80 and 256 samples/cycle. [Yamada et al., 2012b].

A4. EM Field, Power Density and Antenna Measurement

10A dipole antenna has a simple linear structure and this improves the measurement accuracy.
However, since an ordinary dipole antenna employed for the measurement is a half-wavelength
dipole and the total length becomes approximately 5 m at the low end frequency of EMC
measurements, a shortened dipole antenna is used for the measurement in an anechoic chamber.
The antenna factor (AF) for a shortened dipole antenna is usually calibrated by the reference
antenna method at a finite separation. To estimate uncertainty of the reference antenna method,
the measured and calculated results are compared [Morioka et al., 2013].
The response of a field probe is calibrated by the well defined standard field. Such a fieldstrength is generated in a transverse electromagnetic (TEM) waveguide sufficiently below thecutoff frequency of the waveguide. However, above the cutoff frequency the higher-ordermodes perturb the field distribution. For this frequency range a dipole antenna is employed tocalibrate the E-field strength at a location in the anechoic chamber [Morioka, 2011a]. Although
the field generation in an anechoic chamber has an advantage in the frequency band, TEM
waveguides are still useful in terms of compactness. For the use of a TEM cell as a standard
field generator, the electromagnetic field distribution should be accurately evaluated. The
response of a dipole-like probe against the non-uniform field distribution of the TEM cell issimulated and compared with the measured results [Morioka, 2011 b].
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), a bi-conical antenna(from 30 MHz to 300 MHz), and a bi-conical and log-periodic hybrid super broad band antenna(from 30 MHz to 1 GHz) were evaluated for a metrology standard [Kurokawa et al., 2012]. A
new method was proposed for evaluating a far field gain and far field free-space antenna factor
in the near distance. The method is based on a technique of a time-frequency analysis todetermine the frequency dependent antenna distance [Kurokawa et al., 2013]. The method was
examined for calculating the free-space antenna factor of EMI broadband antennas.
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 acalibration service for small loop antennas whose diameters are 10 cm and 60 cm in thefrequency range from 9 kHz to 30 MHz since 2007. The lowest frequency of loop antenna
calibration service was expanded to 20 Hz for the loop antenna with 133 mm diameter in Marchin 2008. AIST and NICT are engaging to improve and simplify the loop antenna calibration
since 2012.
The developments of calibration techniques for short monopole antennas were carrying out

11

by AIST. There have been a number of measurement methods proposed for electrically shortmonopole antennas. A case in point is the equivalent capacitance substitution method, which iscommonly used for monopole antenna measurements. On the other hand, we have proposed anear-field three-antenna method for electrically short monopole antennas. These two absolutemeasurement methods are of quite different origins. In light of this fact, a comparison is madebetween the two measurement methods by means of experiments and simulations, and thedifference observed between the antenna factors is discussed [Ishii et al., 2011]. These studies
are in progress.
AIST started to develop AC magnetic field strength standard since 2008. They will start thecalibration service at 50 Hz, 55 Hz, and 60 Hz in 2011. The method depends on the “Standard
Field Method” using a Helmholtz-coil [Ishii et al., 2012]. AC Magnetic field sensor calibration
service has been expanded from 1 uT up to 150 uT at 50 Hz and 60 Hz, and the uncertainties
were also improved [Ishii, 2013]. This calibration service has been started since April 2013.
Calibration services for the gains of standard horn antennas are being performed from 1 GHz
to 40 GHz specified 21 frequency points using transfer method. An antenna gain calibration
service for standard gain horn antenna (1.7 GHz to 2.6 GHz, 18 GHz to 26.5 GHz, 50 GHz to
110 GHz) has been prepared using three antenna extrapolation method. An antenna factor
calibration service for ridged guide broadband horn antenna (1 GHz to 6 GHz at 3 m) has been
prepared. Far field antenna gain measurement method was proposed in antenna measurements
using the amplitude center location in the Friis transmission formula from the Kern transmission
formula using the phase centers of the antennas [Hirose et al., 2012, 2013]. An antenna patternmeasurement system above 50 GHz using a photonic technology was proposed. This system canminimize the influence of waveguide components because an optical fiber is used as the
mm-wave transmission line [Ameya et al., 2012].
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 evaluate the EMI anechoic chamber performance above 1
GHz, we have proposed an optical feeding radiating antenna for site validation proficiency testof EMI anechoic room [Ameya et al., 2012 b].

A5. Power Attenuation and Impedance Measurements
NMIJ organized three international comparisons as the pilot laboratory. In the
APMP.EM-RF.K8.CL regional metrology organization key comparison (KC) of RF power
measurement, eleven countries participate in the KC. The KC started from June 2012 and12finished its first rotation by 5 countries. The second rotation has been in operation and will
finish August 2014. In the CCEM.RF-K5c.CL key comparison (KC) of scattering parametermeasurement in 3.5 mm coaxial line (100 MHz to 33 GHz), nineteen countries participate in the
KC. The KC started from June 2012 and finished its first rotation by 5 countries. The
comparison will finish September 2015. In the APMC.EM.RF-S5.CL regional metrology
organization supplementary comparison (SC) of characteristic impedance for coaxial lines, ten
countries participate in the SC. The SC will be started from January 2014 and will finish
November 2015.
The calibration services of the scattering parameter have been started for PC7 and Type-N 50
ohms connector in the frequency range of 9 kHz to 18 GHz, for Type-N 75 ohms connector in
the frequency range of 9 kHz to 3 GHz, and for WM-1651 (WR-6) rectangular waveguide in thefrequency range of 110 kHz to 330 GHz. These calibration services are based on use of theoriginally-designed standard terminations in the range of 9 kHz to 10 MHz, and then the long
length air lines as the impedance standards are calibrated using a dimensional measurement andelectrical loss measurement. Subsequently, the dimensionally-derived scattering parameter
calibration has been started. The development of the scattering parameter standard for therectangular waveguide in the frequency range of 50 GHz to 1.1 THz, have been started.
NMIJ developed a new mm-wave power standard in the frequency range from 110 GHz to
170 GHz [Shimaoka, et. al., 2012a, 2013a]. It is an isothermal dry calorimeter, and has a WR-06(WM-864) rectangular waveguide test port. Typical relative expanded uncertainties of a thermal
power meter calibrated using the calorimeter range from 2.7 to 3.1%. NMIJ has been also
developing two wideband waveguide calorimeters in the frequency range from 50 to 75 GHz
and 75 to 110 GHz. We have reported a work concerning to their uncertainty evaluation[Shimaoka, et. al., 2013b]. Their measurement uncertainties have been under evaluation. NMIJ
is developing a new microwave power standard based on the quantum effects. The measurementof a microwave power using the Rabi frequency of vapor-phased cesium (Cs) atoms which is
proportional to the magnetic field strength of the microwave has been reported until 2010.
Incidentally, the Rabi frequency was measured by an atomic candle method which is used for astabilization and reference of microwave strength. Therefore, an optimization of the atomic
candle is important for the atomic microwave power standard. NMIJ optimized the atomic
candle signal [Kinoshita et. al., 2012b, 2013c]. This optimization contributed to understanding
the accuracy and precision of the atomic microwave power standard. In addition, NMIJ has
started to improve the glass cell containing Cs atoms to reduce the uncertainty of the atomic

13

measurement of microwave power. The new cell enable to covert from the magnetic fieldstrength to transmission power of the microwave without an electromagnetic simulation.
An accurate RF and microwave attenuation-measurement technique with a small mismatch
uncertainty in broad continuous frequencies based on the loss measurements to the DUTs infour different phase networks was developed [Widarta et al., 2011a]. The four different
phase-network configurations have been realized by introducing two known phase-shift valuesof airlines to the system. A practical technique to apply the mismatch loss correction in RF andmicrowave attenuation measurements of fixed attenuators as well as variable attenuators as
devices under test has been also developed [Widarta, 2011b]. In the attenuation measurement,
NMIJ developed a unique technique using step attenuator measurements for evaluation of thecomplex reflection coefficients of the source [Widarta, 2012c]. In order to measure highattenuation precisely, a newly double step attenuation measurement technique [Widarta, 2012d]
and a broadband leakage investigation technique [Widarta, 2013d] has been developed. NMIJ
has started to develop an attenuation standard based on the IF substitution method in thefrequency range of 75 -110 GHz (W-band). NMIJ has adopted the IF stabilization techniqueusing a phase-locked loop in order to expanding the frequency range of the attenuation
measurement system into W-band with high stability. Basic performance of the system wasevaluated and a good dynamic range over 60 dB was confirmed [Iida et al., 2013e].
NMIJ has been developing precision RF noise measurement techniques. A variable noise
source using a rotary-vane attenuator was studied in the frequency range of 50 - 75 GHz [Iida etal., 2011c]. An experimental study for determining the resistivity and its temperature coefficientof a transmission line of a coaxial microwave noise source was performed [Iida et al., 2011d].
The uncertainty of a radiometer for RF and microwave noise temperature measurement wasquantitatively evaluated [Iida et al., 2011e].
In recent years, NMIJ has started to study for accuracy evaluation of a terahertz spectroscopy.
In the attenuation (or transmittance) measurement by a terahertz time-domain spectrometer(THz-TDS), it is important to evaluate its linearity. For validation of the THz-TDS, NMIJ
developed a metalized-film attenuator (MFA) that can be used in both focused and collimatedTHz beam configurations [Iida et al., 2012e, 2012f, 2013f]. A method of power linearity
evaluation by using the MFA has been proposed [Iida et al., 2011f, 2012g, 2013g, 2013h].
In the joint research project with the National Physical Laboratory, UK, NMIJ achieved thedimensional calibration capabilities of millimeter-wave coaxial line, i.e. 1.85 mm coaxial line,
and waveguide, i.e. WM-864 waveguide size, and good agreement between both laboratories

14[Horibe et al., 2010a, 2012i, 2012m, Shelton et. al., 2012r]. Then NMIJ had been developed themetrology standards in the both coaxial [Horibe et al., 2010b, 2011g, 2012k] and waveguide,
uncertainty evaluation method of waveguide vector network analyzers (VNA) [Horibe et al.,2011h, 2012j, 2012n, 2012o, 2012p, 2013i] over 110 GHz up to 1.1 THz. In this research, NMIJ
developed a new design of waveguide flange, connection clamp and VNA stage for establishingaccurate and quick connection of waveguide standard devices and components [Horibe et al.,2011i, 2012l, 2013k, 2013m].
The calibration and testing methods of Artificial Main Network used in Electromagnetic
compatibility testing has been developed using radio frequency impedance standards[Kishikawa et al., 2012q, 2013j, 2013n]. NMIJ has launched to research material
characterization and on-wafer measurement techniques in the frequency range between
microwave and millimeter wave. In the collaborate work with the King Mongkut's Institute ofTechnology Ladkrabang (KMITL), Thailand, uncertainty evaluation method and uncertainty
optimization technique have been developed for material characterization based on thetransmission and reflection method. Further material characterization techniques, split cylinder,
ring-down cavity [Kato, 2013o] and free-space measurement methods, are being researched. In
the on-wafer techniques, the method to achieve a metrological traceability has been established[Horibe, 2013l].

15

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Hobiger T., et al. [2011b], “VLBI analysis with c5++ - status quo and outlook,” Proceedings ofthe 20th EVGA.

Horibe M., Shida M. and Kishikawa R. [2010a], “Complete Characterization of Rectangular
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Horibe M, Ridler N., Salter M. and Eio C. [2010b], “Characterization and Verification of
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Horibe M., Ridler N., and Salter M. [2011g], “New Calibration Technique for Coaxial Network
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Horibe M., and Ridler N. [2012i], “Comparison Between NPL and NMIJ of Diameter andScattering Parameter Measurements of Precision 1.85 mm Coaxial Air Lines,” IEEE Trans.
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Horibe M. and Kishikawa R. [2012j], “Establishment of S-parameter Standards of Rectangular
Waveguide at Millimeter-wave and THz Frequencies,” PIERS2012 digests.

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Horibe M. and Kishiakwa R. [2012l], “Performance of New Design of Waveguide Flange for
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Horibe M. Ridler N. and Wilson A. [2012m], “Traceability via Precision Dimensional
Measurements of WM-864 (WR-03) Waveguide Standard Shims Including Comparison
between NPL and NMIJ,” 79th ARFTG conference digests.

Horibe M., and Kishikawa R. [2012n], “Traceability to National Standards for S-parameter
Measurements in Waveguide at 1.1 THz,” 2012 Conference on Precision Electromagnetic
Measurements (CPEM) Digests.

Horibe M., and Kishikawa R. [2012o], “Confidence of Waveguide VNA Measurement in the
Frequency Range of W-band and D-band,” IRMMW-THz2012 conference digests.

19Horibe H. and Kishikawa R. [2012p], “Characterization of Quarter Wavelength Line as
Measurement Standard for Scattering Parameter in the Frequency Range of W-band andD-band,” IRMMW-THz3012 conference digests.

Horibe M. and Kishikawa R. [2013i], “Metrological Traceability in Waveguide S-parameter
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Horibe M., and Kishikawa R. [2013k], “Comparing Accuracy of Waveguide VNA Measurement
Calibrated by TRL Calibration Using Different Length of Line Standard in Terahertz Band,”
ARFTG conference digests.

Horibe M. [2013l], “Metrological Traceability Challenge for On-Wafer S-parameter
Measurement at Microwave and Millimeter-wave length,” AP-RASC2013 Conference digests.

Horibe M. and Kishikawa R. [2013m], “Investigations of Capability of Connection
Repeatability for Waveguide with Different Size Apertures,” 81st ARFTG conference digests.

Hosaka, K., Inaba, H., Akamatsu, D., Yasuda, M., Sugawara, J., Onae, A., and Hong, F.-L.
[2013], “A Fabry-Perot Etalon with an Ultralow Expansion Ceramic Spacer,” Jpn. J. Appl. Phy.,
52, pp. 032402.

Ichikawa R., et al. [2011], “Precise Frequency Transfer Experiments using VLBI and otherTechniques,” The XXX General Assembly and Scientific Symposium of the International Union
of Radio Science (URSI GASS 2011).

Iida H., T. Inaba, Y. Shimada and K. Komiyama [2011c], “Uncertainty of a Millimeter-Wave
Variable Noise Source using a Variable Attenuator,” IEEJ Trans. Fundamentals and Materials,
131, no. 4, pp. 302-303 (in Japanese).

Iida H., T. Inaba, Y. Shimada and K. Komiyama [2011d], “A Study on the Estimation of Noise
Temperature of a Microwave Standard Noise Source,” IEEJ Trans. Fundamentals and Materials,
131, no. 4, pp. 300-301 (in Japanese).

20

Iida H., Y. Shimada and K. Komiyama [2011e], “Evaluation of Type B Uncertainty of aRadiometer for RF and Microwave Noise Temperature Measurement,” IEEJ Trans.
Fundamentals and Materials, 131, no. 4, pp. 231-238 (in Japanese).

Iida H., Y. Shimada, M. Kinoshita, H. Kuroda, K. Kitagishi and Y. Izutani [2011f], “PowerLinearity Measurement in Terahertz Time-Domain Spectroscopy using Metalized Film
Attenuators,” Jpn. J. Appl. Phys. 50, no. 12, 128004.

Iida H., M. Kinoshita, Y. Shimada, H. Kuroda, K. Kitagishi, and Y. Izutani [2012e],“Comparison of transmittance measurement between high-resistivity float-zone silicon andmetalized-film attenuators in focused-beam THz-TDS,” Tech. Dig. of the 7th Asia-PacificMicrow. Photon. Conf., PB-1.

Iida H., M. Kinoshita, Y. Shimada, H. Kuroda, K. Kitagishi, and Y. Izutani [2012f],“Experimental investigation of a metalized-film attenuator for validation of terahertz
time-domain spectroscopy,” The 37th Int’l Conf. on Infrared, Millimeter and Terahertz Waves,
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Iida H., M. Kinoshita, Y. Shimada, H. Kuroda, K. Kitagishi, and Y. Izutani [2012g], “Linearity
evaluation of THz-TDS system by a step attenuator using metalized films,” 2012 Conference on
Precision Electromagnetic Measurements (CPEM) Digests, pp. 660-661.

Iida H. and K. Fujii [2013e], “Basic Study for Development of Attenuation Standard in W-band,”
Ext. Abstr. 74th Autumn Meet., Japan Society of Applied Physics, 16a-C8-2 (in Japanese).

Iida H., M. Kinoshita and Y. Shimada [2013f], “Measurement of optical properties of ametalized-film attenuator at terahertz frequencies using a time-domain spectrometer,” Int’lWorkshop on Optical Terahertz Science and Technology Ext. Abstr., pp. 339-339.

Iida H., M. Kinoshita, Y. Shimada, H. Kuroda, K. Kitagishi, and Y. Izutani [2013g], “Validationof power linearity in terahertz time-domain spectroscopy using a programmable step attenuator,”
IEEE Trans. Instrum. Meas., 62, no. 2, pp. 1801-1806.

21

Iida H., M. Kinoshita and Y. Shimada [2013h], “Improvement of transmission characteristics ofa THz step attenuator,” The 38th Int’l Conf. on Infrared, Millimeter and Terahertz Waves,
Mo-P1-35.

Imai Y., Sugiyama K., Nishi T., Higashitani S., Momiyama T., and Kitano K. [2013],“Single-ion spectroscopy of the 2S1/2－2D5/2 clock transitions in Yb+ towards search for temporalvariation of the fine structure constant,” Abstract of the 12th Asia Pacific Physics Conference(APPC12), B3-PWe-21, Makuhari (Japan), p.927, July.

Inaba, H., Hosaka, K., Yasuda, M., Nakajima, Y., Iwakuni, K., Akamatsu, D., Okubo, S., Kohno,T., Onae, A., Hong, F.-L. [2013], “Spectroscopy of 171Yb in an optical lattice based on laser
linewidth transfer using a narrow linewidth frequency comb,” Opt. Exp., 21，pp.7891-7896.

Ishii M., S. Kurokawa, and Y. Shimada [2011], “Comparison between three-antenna method andequivalent capacitance substitution method for calibrating electrically short monopole antenna,”
Proceedings of 2011 IEEE International Symposium on Electromagnetic Compatibility (LongBeach), pp. 101 – 106, Aug.

Ishii M., S. Kurokawa, Y. Shimada [2012], “AC Magnetic Field Standard for Magnetometer
Calibrations at NMIJ,” in Proc. CPEM2012, pp. 488-499, Washington, USA, July.

M. Ishii, R. Ketzler, M. Albrecht, S. Kurokawa [2013], Y. Shimada, “Improvement of Formulaand Uncertainty of the Reference Magnetic Field for AC Magnetometer Calibration,” IEEE
Trans. Instrum. Meas., vol. 62, no. 6, pp. 1443-1449, June.

Ito H., S. Nagano, M. Kumagai, M. Kajita, and Y. Hanado [2013], “Terahertz Frequency
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Iwakuni, K., Inaba, H., Nakajima, Y., Kobayashi, T., Hosaka, K., Onae, A., and Hong, F.-L.
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22

Kajita M., M. Abe, M. Hada, and Y. Moriwaki [2011 a], “Estimated accuracies of pure XH+ (X:even isotopes of group II atoms) vibrational transition frequencies: Toward the test of thevariance in mp/me ,” J. Phys. B: At. Mol. Opt. Phys. 44, 025402 1-7.

Kajita M., G. Gopakumar, M. Abe, and M. Hada [2011 b], “Elimination of the Stark shift fromthe vibrational transition frequency of optically trapped 174Yb 6Li molecules,” Phys. Rev. A 84,
022507 1-6.

Kajita M., G. Gopakumar, M. Abe, and M. Hada [2012 a], “Accuracy estimations of overtone
vibrational transition frequencies of optically trapped 174Yb6Li molecules,” Phys. Rev. A 85,
062519 1-8.
Kajita M. and M. Abe [2012 b], “Frequency uncertainty estimation for the 40CaH+ vibrationaltransition frequencies observed by Raman excitation,” J. Phys. B: At. Mol. Opt. Phys.45,
185401 1-5.

Kajita M., G. Gopakumar, M. Abe, and M. Hada [2013], “Sensitivity of vibrational
spectroscopy of optically trapped 88Sr6Li and 40Ca6Li molecules to variations in mp/me ,” J. Phys.
B: At. Mol. Opt. Phys. 46, 025001, 1-5.

Kaneko N., M. Maruyama, and C. Urano [2011], “Current Status of Josephson Arbitrary
Waveform Synthesis at NMIJ/AIST,” IEICE Trans. Electron., E94-C No.3, pp.273-279.

Kaneko N., M. Maruyama, and C. Urano and S. Kiryu [2012a], “Review of Josephson
Waveform Synthesis and Possibility of New Operation Method by Multibit Delta-Sigma
Modulation and Thermometer Code for Its Further Advancement,” Jpn. J. Appl. Phys. 51,
pp.010116(7).

Kaneko N., T. Oe, A. Domae, T. Abe, M. Kumagai, and M. Zama [2012b], “Development ofHigh-Stability Metal-foil Standard Resistors for DC and AC Measurements,” Proceedings of theNCSLI 2012 Workshop & Symposium.

23Kaneko N., T. Oe, A. Domae, T. Abe, M. Kumagai, and M. Zama [2012c], “Development ofHigh-Stability Metal-Foil Resistors for DC and AC Measurements,” NCSLI Measure J. Meas.
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Kaneko N., A. Domae, T. Oe, J. Schurr, F. J. Ahlers, and S. Kiryu [2012e], “Investigation of
On-chip Double-shieled QHR Device in AC Regime,” CPEM2012 Digest, pp.193-194.

Kaneko N., A. Domae, T. Oe, J. Schurr, F. J. Ahlers, and S. Kiryu [2013a], “First attempt todevelop an on-chip double-shielded QHR device for use in ac measurements,” IEEE Trans.
Instrum. Meas., 62, pp.1743-1748.

Kaneko N. [2013b], “Progress of Electrical Standards and the future Revision of theInternational System of Units,” Measurement Standards and Metrology Management, 63 No.1,
pp.6-11.

Kato Y. Ameya M., Horibe M. and Kurokawa S. [2013o], “A Proposal of a New Permittivity
Measurement Method for Low-Loss Materials”, Proceedings of European Microwave Week
2013, pp.1287-1290.

Kinoshita M., K. Shimaoka, Y. Shimada [2012b], “Optimization of the Atomic Candle Signal
Used for Microwave Power Standard Based on the Rabi Frequency,” 2012 Conference on
Precision Electromagnetic Measurements (CPEM) Digest, pp. 114-115.

Kinoshita M., K. Shimaoka, Y. Shimada [2013c], “Optimization of the Atomic Candle Signal
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Kishikawa R. and Horibe M. [2012q], “Development of S-parameter Standard for Coaxial 3.5
mm Connectors in the Frequency Range from 10 MHz to 100 MHz,” 2012 Conference on
Precision Electromagnetic Measurements (CPEM) Digests.

Kishikawa R., and Horibe M. [2013j], “Establishment of S-parameter Traceability for 3.5 mm
Coaxial Lines from 10 MHz to 100 MHz,” IEEE Tans. Instrum. Meas.

24

Kishikawa R. and Horibe M. [2013n], “Metrological Standard of S-parameter for 2.92 mm
Coaxial Lines,” AP-RASC Conference Digests.

Kon S., and T. Yamada [2011], “Uncertainty Evaluations of an AC Shunt Calibration Systemwith a Load Effect Reduction Circuit,” IEEE Trans. Instrum. Meas., 60, No.7, pp.2286-2291.

Kon S., and T. Yamada [2012a], “Development of an Extremely Precise Buffer Amplifier for AC
Shunt Standards at Audio Frequencies,” Electrical Engineering in Japan, 178, No.4, pp.24-31.

Kon S., and T. Yamada [2012b], “Uncertainty Estimations of an Evaluation System for a HighAccuracy and Wideband Transconductance Amplifier,” CPEM2012 Digest, pp.482-483.

Kon S., Y. Kasai, M. Murakawa and T. Higuchi [2013a], “Visualization System for ElectricalPower Consumption and its Evaluation,” IEEJ Transactions on Electrical and Electronic
Engineering, 7, S1, pp.14-18.

Kon S. and T. Yamada [2013b], “Frequency Characterizations of Voltage and Current
Transducers for Evaluation of Phasor Measurement Units,” The 10th IEEE International
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Kon S., and T. Yamada [2013c], “Expansion of the frequency range of ac shunt calibration
system and its verification,” SICE annual conference 2013 conference proceedings,
pp.1671-1672.

Kon S., and T. Yamada [2013d], “Characterization of high-accuracy, wideband transconductance
amplifiers up to 100 kHz,” IEEE Trans. Instrum. Meas., (accepted).

Kondo, T., et al. [2012], “VLBI Application for Time and Frequency Transfer, and Comparison
with Other Techniques,” Shanghai Astronomical Observatory "New Technologies in Astronomy”
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Koyama, Y. [2012], “The Use of Very Long Baseline Interferometry for Time and Frequency

25

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Koyama, Y., et al. [2013], “Remote Frequency Comparison with Very Long Baseline
Interferometry,” 2013 Asia-Pacific Radio Science Conference (AP-RASC2013).

Kurokawa S., M. Hirose, M. Ameya [2012], “Three antenna method for a hybrid broad band
antenna using time domain and pulse compression technique,’’ in 2012 Conference on
Precision Electromagnetic Measurements (CPEM) Digests, pp.634-635, Washington,
USA, July.

Kurokawa S., M. Hirose, M. Ameya [2013], “Far Field Gain Estimation Method for Japanese
Broadband Antenna Standard Using Time-frequency Analysis,’’ in Proc. Piers2013, pp.838-842,
Stockholm, Sweden, Aug.

Matsubara K., H. Hachisu, Y. Li, S. Nagano, C. Locke, A. Nogami, M. Kajita, K. Hayasaka, T.
Ido, and M. Hosokawa [2012], “Direct comparison of a Ca+ single-ion clock against a Sr latticeclock to verify the absolute frequency measurement,” Opt. Exp. 20, 22034.

Morioka T. [2011a], “Tracing E-field probe responses to the dipole antenna factor,” in Proc.
IEEE Int. Symp. Electromagn. Compat., pp. 1-5, Long Beach, CA., USA, Aug.

Morioka T. [2011b], “Response of a short dipole probe to a non-uniform E-field of a TEM cell,”IEEE Trans. Instrum. Meas., vol. 60, no. 7, pp. 2709-2714, July.

Morioka T., M. Yamanaka, and K.Hirawsawa [2013], “Shortened dipole antenna factors by thereference antenna method at a finite separation,” in Proc. IEEE Int. Symp. Electromagn.
Compat., pp. 439-444, Denver, CO., USA, Aug.

Nagano S., H. Ito, M. Kumagai, M. Kajita, and Y. Hanado [2013], “Microwave synthesis from acontinuous-wave terahertz oscillator using a photocarrier terahertz frequency comb,” Optics
Letters, 38, 12, pp.2137 -2139.

Nakamura M., Takahashi Y., Amagai J., Gotoh T., Fujieda M., Tabuchi R., Hama S., Yahagi Y.,

26

Takahashi T. and Horiuchi S. [2013], “Time Comparison Experiments Between the QZS-1 andits Time Management Station,” NAVIGATION, Journal of the Institute of Navigation, 60, No. 4,
319-324, DOI: 10.1002/navi.46, Dec.

Ovsiannikov, V. D., V. G. Pal’chikov, A. V. Taichenachev, V. I. Yudin and H. Katori [2013],“Multipole, nonlinear, and anharmonic uncertainties of clocks of Sr atoms in an optical lattice,”
Phys. Rev. A 88, pp. 013405.

Oe T., K. Matsuhiro, T. Itatani, S. Gorwadkar, S. Kiryu, and N. Kaneko [2011], “Improvementof yield ratio of ohmic contact to GaAs/AlGaAsheterostructure by application of SiO2 protective
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