COMMISSION A : Electromaganetic Metrology (November 2004 - October
2007)
Edited by Mizuhiko Hosokawa
A1. Time and Frequency Standards and Time Transfer Technique
In Japan, the researches and developments on Time and Frequency (T&F) Standards and Time
Transfer Technique are mainly carried out in the National Institute of Information andCommunications Technology (NICT) and National Metrology Institute of Japan (NMIJ).
NICT headquarters has been keeping UTC(NICT) and Japan Standard Time (JST). A maximum ofeighteen Cs atomic clocks and four hydrogen masers are used for making the timescale. A new JST
generation system including various upgrades was completed after four years for development andstarted operation in February 2006 [Nakagawa et al. 2005, Hanado et al. 2006, 2007]. The timescalealgorithm of UTC(NICT) has been investigated by NICT staffs [Hosokawa et al. 2005], and some
improvements have been added to suppress the undesirable effects of anomalous clocks.
As for dissemination, two LF radio stations continuously transmit 40kHz and 60kHz respectively of
JST time signal and the standard frequency signal. The field strength of LF signals during transmission
was theoretically modeled. [Wakai et al. 2005]. To verify this model, two observation cruises on theSoutheast Asian line and the North Pacific line using container ships were carried out in 2007. Resultsof the observation will be submitted to ITU-R WP7A in 2008. Public dial up time service via
telephone lines has satisfied a large number of accesses.
NICT has started the accuracy evaluations of TAI unit by the Cs atomic fountain primary frequency
standard NICT-CsF1 [Kumagai et al., 2005, 2006a, b, 2007]. Frequency uncertainty of NICT-CsF1
was estimated as 1.9x10-15 [CIRCULAR T 221].
NICT has developed an engineering model of space-borne hydrogen maser atomic clock. The
weight of the physical part is reduced from 36.5 kg (breadboard model) to 27 kg. [Ito et al. 2007a].
NICT newly developed a Network Time Protocol (NTP) server with high-performance and started apublic time service from 2007. The number of access is about fifteen million per day [Toriyama et al.
2007]. A new protocol for high-speed network time transfer has been investigated by using this server[Iwama et al. 2006, 2007].
On-site calibration system for frequency standards at NICT was equipped with a new system andapproved by a peer review in 2006. Accordingly measurement uncertainty was improved from 10-13 to
5x10-14. NICT has also started a remote calibration system since 2005[Saito et al. 2006].
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 placeof GPS data [CIRCULAR T 231]. Researches about GPS carrier phase method and TWSTFT for along baseline are in progress. NICT is developing a new TWSTFT method using dual Pseudo
Random Noises (PRN). NICT and USNO plan to install a new TWSTFT relay station in Hawaii for
their link.
To distribute precise frequency by optical fiber, basic experiment using delay control has been
started in a lab and a field.
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 has been launched on
December 2006. Both code phase and carrier phase showed consistent result and capability tomonitor on-board atomic clock.
The time transfer subsystem (TTS) of the engineering model (EM) of the Quasi-Zenith Satellite
System (QZSS) passed the environmental test, and the development of its proto-flight model (PFM)
has been started. Its ground system is also been developing. The first QZS will be launched in 2010.
NICT has developed an engineering model of space-borne hydrogen maser atomic clock. The
weight of the physical part is reduced from 36.5 kg (breadboard model) to 27 kg. [Ito et al. 2007a].
In NMIJ, following researches have been conducted.
Primary Frequency Standards; NMIJ has made the calibration of the International Atomic Time(TAI) with the Cs atomic fountain frequency standard, NMIJ-F1, a few times per year with a
combined uncertainty of 3.9x10-15 since September 2005. This uncertainty is larger than that in the
preliminary evaluations [Kurosu et al. 2004, Yanagimachi et al. 2005] and is limited by the evaluation
uncertainty of a collision shift. We have changed the trapping scheme of atoms from MOT to opticalmolasses, in order to improve the long term stability. Laser systems, optics, and microwave systems
have been upgraded for a better operationality [Yanagimachi et al. 2006]. NMIJ-F1 will be used as areference oscillator for the evaluation of the optical lattice clocks in NMIJ, the development of oursecond fountain (NMIJ-F2), as well as used for the TAI contribution. Recently, we have started theconstruction of NMIJ-F2 to reduce the uncertainty.
Ultra-stable microwave oscillator; NMIJ has developed two cryogenic sapphire oscillators (CSOs)
for local oscillator of a Cs atomic fountain and reference signal of a femtosecond mode-locked laser.
The CSOs employ a loop oscillator configuration, which is servo controlled by a Pound-type
frequency stabilization scheme and a power control servo. These oscillators exhibited a fractionalfrequency stability of 1.1 × 10-15 at an averaging time of 1 s [Watabe et al. 2006]. For averaging times
between 2 s and 640 s the measured oscillator fractional frequency instability was below 10-15 with aminimum of 5.5 × 10-16 at an averaging time of 20 s. Also, we have implemented optical frequency
synthesis from a CSO using a fiber-based frequency comb. The synthesized optical frequency
exhibited an Allan deviation of ∼6 × 10-14τ-1/2 for averaging times between 1 s and 100 s and aminimum frequency instability of 3.0 × 10-15 at averaging times of 1280 s by comparing a rubidium
two-photon stabilized laser. The short-term frequency stability was limited by the rubidium
two-photon stabilized laser [Watabe et al. 2007].
Time Keeping; Four cesium atomic clocks with high-performance beam tubes (Agilent 5071A) andthree active hydrogen maser frequency standards are operated for time keeping in NMIJ. One of thehydrogen 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 GPS receiver is one of the maininternational time and frequency transfer tools. In addition, the Two Way Satellite Time and Frequency
Transfer (TWSTFT) have been conducted between NICT and several East Asia institutes using
JCSAT-1B and the multi-channel modem. Starting from September 2007, TWSTFT between NMIJ
and PTB has been constructed using IS-4 satellite.
GPS data analysis software named GCAST for short base line, such as 50 km, was developed at
NMIJ. Its main purpose is the data analysis for the time and frequency transfer between NMIJ in
Tsukuba and the University of Tokyo in Tokyo to use for the frequency evaluation of the Sr opticallattice clock developed by the University of Tokyo. GCAST uses the broadcast navigation data and it
can provide frequency uncertainty of 1-2 x 10-15 at averaging time of 1 day for 50 km baseline [Fujii etal. 2006, Imae et al. 2007].
An optical fiber bidirectional frequency transfer system using Wavelength Division Multiplexing
technology is also studied in NMIJ as future precise time and frequency comparison technique[Amemiya et al. 2006b].
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 andInternet. NMIJ's remote frequency calibration service has been started since 2006 to the calibrationlaboratories. NMIJ has also started to develop the user equipment for the end users of the remotefrequency calibration service [Imae et al. 2006]. 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 anuncertainty of less than 1×10-12 at an averaging time of one day [Amemiya et al. 2006a].
Other activities related to Time and Frequency standards; One of other groups in AIST has been
focusing its efforts on the development of a remote synchronization system for an onboard crystal
oscillator (RESSOX) of the Japanese Quasi-Zenith Satellite System (QZSS). This system cansynchronize ground time standard and the onboard crystal oscillator within 10 ns using signal delay
models and pseudo-ranges of QZSS positioning signals [Tappero et al., 2006]. Through hardware
simulation, AIST has demonstrated that synchronization within a few nanoseconds can be realized[Iwata et al., 2006, 2007].

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. havemeasured the absolute frequency of the 4s2S1/2 - 3d2D5/2 forbidden transition with the measurement
error of +-1.4kHz [Matsubara et al., 2007b]. To observe the a narrow linewidth laser is being
developed. Its linewidth is 66 Hz and the floor of the Allan variance is 8.3x10-14 at an averaging timeof 32 s. The long term frequency drift was 0.5 Hz / s [Li et al., 2007b].
To measure the laser frequency, NICT is developing two optical frequency comb based oncommercially available Ti:sapphire laser [Ito et al., 2006, Nagano et al., 2006]. They measure therelative frequency stability between two combs and estimate the stability as 2x10-14 and 1x10-15 ataveraging time of 1 s and 100 s respectively [Ito et al., 2007].
Various time and frequency standards related researches have been conducted in NICT and some
Unversities, such as on atomic and molecular physics [Fukuda et al. 2005a, b, 2006, 2004 a, b, Kajita
2005a, b, c, d, 2006a, b, c, d, e, f, Matsubara et al. 2005c, 2006a, b, 2007a, b] and laser frequency
stabilization [Li et al. 2005a, b, 2006a, b, 2007a, Matsubara et al. 2005a, b]. Dr. Kajita has proposed an
infrared frequency standard based on trapped NH molecule. He estimate the uncertainty of the clocktransition can potentially be reduced to lower than 1E-17 [Kajita, 2006].
NMIJ and Katori Group in Tokyou University have obtained the following results.
Activities in optical frequency region; In the optical lattice clock scheme, a collision-shift-free
atomic clock was proposed and realized by using a one-dimensional lattice clock with a spin-polarized
fermionic isotope [Takamoto et al., 2006]. Katori group and NMIJ have measured the transition
frequency for the Sr lattice clock with an uncertainty of 9.8×10-15 using an optical frequency comb
referenced to the SI second [Takamoto et al., 2006]. In October 2006, the International Committee of
Weights and Measures (CIPM) decided to adopt the Sr lattice clock as one of “the secondary
representations of the second”.
NMIJ has conducted the following researches on the optical measurements and standards; One is thedevelopment of an Yb optical lattice clock [Yasuda et al., 2007]. Vacuum system and laser systems
have been prepared.
Magneto-optical trapping of cold Yb atoms was realized using anintercombination transition (1S0 - 3P1; 556 nm). The experiment is under way toward trapping
ultracold atoms in the optical lattice. A probe laser to drive the 1S0 - 3P0 transition in Yb atoms,
which is stabilized to a high finesse Fabry-Perot etalon, is also being developed. A long-term
measurement of optical frequencies has been demonstrated by using a fiber-based frequency comb
[Inaba et al., 2006a]. Doppler-free spectroscopy using optical frequency synthesizer has been
demonstrated by using a mode-locked Ti:sapphire laser and a continuous-wave optical parametricoscillator [Inaba et al., 2006b].
Prof. Takahashi et al. (Kyoto University) have obseved a Bose-Einstein condensate in a bosonicisotope of ytterbium 170Yb [Fukuhara et al., 2007]. Generation of a BEC in an even isotope of Yb ishelpful in optical lattice clock using even isotopes of alkaline-earth-metal-like atoms.
Suzuki et al.(Tohoku University) have developed a ultralow noise and narrow linewidth DFB
Er-doped fiber laser. A linwidth of the fiber laser was estimated as 6kHz [Suzuki et al., 2007].
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 and so on, areimplemented in Electricity and Magnetism division of National Metrology Institute of Japan (NMIJ)
and Nanoelectronics Research Institute of Advanced Industrial Science and Technology (AIST). Mostof these standards are realized based on Josephson arrays, or Quantum Hall Effect (QHE).
Concerning the research on Josephson arrays, fabrication of 5 V programmable Josephson arrays
operated at 10 K has been finished. By connecting two 5 V samples in series, 10 V programmable
Josephson voltage standard has been completed. [Shoji, A. et al., 2006-2007].
In order to realize just 10 kohm resistance standard based on the QHE, Quantum Hall Resistance(QHR) arrays are being developed. Using the series and parallel combination of QHE bars, various
values of resistance are expected to be realized. Fabrication of single QHE bars used for QHR arrays
has been finished. [Kaneko, N. et al., 2006-2007].
In the development of new device for ac/dc transfer staandard, planner multi-junction thermal
converters (PMJTC) are being developed for the use of calibration of ac/dc current differences up to 1
A. A prototype of the PMJTC has been developed. [Fujiki, H., 2006-2007].
Calibration range for both ac resistance standards and inductive voltage dividers has been expandedfrom 10 ohm to 100 kohm at 1 kHz and 10 kHz [Domae, A. et al., 2005-2007], and the ratios of 0.01
to 1.0 at 200 Hz, 400 Hz, 1 kHz and 10 kHz [Sakamoto, N. et al., 2005-2007], respectively. Standards
for loss angle of capacitors have been developed for 10 pF to 10 microF. [Nakamura, Y. et al.,2005-2006].
NMIJ has designated Japan Electric Meters Inspection Corporation (JEMIC) as an institute to be
responsible for national standards of power and energy at 45 - 65 Hz. [Nakamura, Y. et al., 2007].
A4. EM field, Power density and antenna Measurement
In the field of precision measurements for EM field, a dipole antenna is a simple linear antenna andit is often used as a reference antenna. Since most of the electromagnetic
compatibility/electromagnetic interference (EMC/EMI) measurements are carried out on an open-area
test site, the antennas used in the measurement should be calibrated above the ground plane. Several
calibration methods for the antenna factor (AF) have been proposed and widely applied by the
metrology institutes. However, although a critical quantity sated in their certificate to trace thecalibration chain is uncertainty, detailed uncertainty analysis associated their calibration has not been
published. Uncertainty analysis strictly following the GUM for the three-antenna method and thereference antenna method was published [Morioka, et al. 2006]. The final uncertainty after these two
methods is reported 0.7 dB (k=2) in the frequency range from 30 to 1000 MHz. Some EMC
procedures require the measurements above 1 GHz. Measurements in an anechoic chamber get
common in this frequency range. Since the measurement environment is quasi-free space, the freespace 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.
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 was 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 examinedfor calculating the free-space antenna factor of a log-periodic antenna widely used for EMI
measurement [Kurokawa et al. 2005, 2006].
The developments of calibration techniques for loop antennas were carrying out by AIST and NICT.
AIST started to develop the calibration method since 2002. Basically they calibrate the standard loop
antenna by the “3-Antenna Method [Ishii et al. 2005]” and the customer’s loop antennas by the“Reference Antenna Method [Ishii et al. 2007a]”. In order to simply calibrate the standard loop
antenna, they also studied another new calibration method “Measuring Impedance Method [Ishii et al.
2007b]”. AIST also started 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.
On the other hand, NICT and Tohoku University are developing the loop antenna calibration system.
Basically, their method depends on the “Standard Field Method”. It is a novel method, because thesystem does not need a vacuum thermocouple to measure the current on the antenna element[Nakajima et al. 2005].
A novel optical system was proposed to measure S-parameters in one-path 2-port calibration[Hirose et al 2007a]. This system can completely replace coaxial cables by optical fibers in RF
measurements using a vector network analyzer that require many kinds of calibration techniques forthe accurate measurements. Using this system, antenna measurements were done blow 2 GHz andproved that the system realizes the dynamic range of 45 dB and the difference within 0.03 at areflection coefficient compared to the coaxial cable system. This system is especially promising in
antenna measurements because it realizes measurements without metallic cables.
A novel method was proposed in antenna measurements [Hirose et al. 2007b]. The method realizesantenna measurements in full 2-port calibration that requires only open-short-load calibration at eachport 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 throughcalibration is especially important in antenna measurements because we are released from the hardlabor to mate cable connectors directly or to other cable connectors.
A method and a simple equation for determining the magnetic complex antenna factor (M-CAF) ofa shielded loop antenna are presented. The investigated shielded loop antenna has two output ports ofwhich outputs are differentially combined in time domain. The low-directivity of this loop antenna isuseful for mapping magnetic fields. The proposed method is based on an equivalent circuit of theantenna system. The derived equation makes it possible to determine the M-CAF from the calculated
effective length of the loop element and the measured reflection coefficient at an output port. The
proposed method is confirmed by comparison between the waveform reconstruction using the M-CAF
and the theoretical calculation for an electromagnetic pulse radiated from a monopole antenna on a
ground plane. [Kohmura, 2006]
A method and configuration for generating a calculable electromagnetic pulse is proposed in which
the electromagnetic pulse is radiated from a small monopole antenna placed near the edge of asemi-infinite ground plane. The monopole antenna is excited by an impulse train. The radiated electricfield at a distance from the edge is calculated by the waveform of the excited impulse with theassistance of the Uniform Theory of Diffraction (UTD) to include the effect of diffraction from theedge of the ground plane. The electric field is also reconstructed by signal processing using thecomplex antenna factor (CAF) of a receiving wide-band antenna. The estimated systematic effects andthe agreement of the calculated and reconstructed waveforms show that the generated electromagnetic
pulse has a possibility to be used as a reference wave for electromagnetic pulse measurements.
[Iwasaki, 2006]
A5. Power, Attenuation and Impedance Measurement
A direct comparison calibration system for WR-15 waveguide RF power sensors (60 GHz) was
developed in NMIJ in 2004 to carry out the calibration system of millimeter wave power in addition toa calorie meter system for microwave power. After that, an international peer review and an ISO/IEC
17025 assessment of the quality management system for 2.9 mm coaxial RF power meter calibrationin NMIJ were performed, and the quality management system was accredited by an accreditationbody(National Institute of Technology and Evaluation) in February 2005. The report of
CCEM.RF-S1.CL international comparison of RF power measurement with 2.4 mm connectors, inwhich NMIJ had participated in, in April 2004, was approved by BIPM in October 2005[2005].
Further, a direct comparison calibration system for 2.4 mm coaxial waveguide RF power sensors (fullband) was developed in NMIJ in 2005 in addition to a caloriemeter system to extend the frequency
range of calibration service. Besides, the frequency range of the NMIJ WR-15 waveguide calibration
system was extended from only a point frequency of 60GHz to full band (from 50 GHz to 75 GHz) in2006. In addition, a direct comparison calibration system for WR-10 waveguide RF power sensors (Wband) was developed in NMIJ in 2006.
A measuring system of the reflection coefficient of reference power source of RF power meters wasdeveloped, and the technology was presented in CPEM 2006 in Turin, Italy [Shimaoka et al.
2006a].The result of CCEM.RF-S1.CL international comparison of RF power measurement with 2.4
mm connectors was presented in CPEM 2006 in Turin, Italy [Crowley et al. 2006b]. A new study of an
atomic RF power standard started in 2007. This new technology is based on the observation of the
Rabi oscillation of the double resonance spectrum of Cs vapor. The absolute RF power in WR-90
waveguide in a frequency of 9.2 GHz is determined by converting the frequency of the Rabi
oscillation to the field strength in the waveguide. As a result of a basic experiment, a linear response of
the Rabi oscillation frequency to input RF power was observed in 2007. Now, NMIJ is a pilot
laboratory of APMP.RF-K8.CL RMO key comparison of RF power measurement with Type N
connector. This RMO key comparison is now in preparation.
As for the noise standard, National Meteorology Institute of Japan (NMIJ) has extended a
microwave radiometer system for the measurement of noise sources with WR42 waveguide output
flanges in the frequency range from 18 GHz to 26.5 GHz. An uncertainty analysis for the thermalnoise measurement is applied to the total power radiometer system which is represented by aradiometer equation [Shimada 2006]. NMIJ has been also developing the original cryogenic standard
noise source with WR90 waveguide flange by using the sliding short method which is cooled by liquid
nitrogen. The estimated value of the noise temperature of the original noise source is good agreementwith the noise temperature which is measured by the calibrated radiometer. Uncertainties of theoriginal noise source are being evaluated in detail now.
The development of a new broadband RF attenuation measurement system was begun in 2000 at the
NMIJ, to meet the increasingly growing demands for accurate, traceable, and broad-band standards
which have a high attenuation range. The system was planned to cover the frequency range of 10 MHz
to110 GHz and the attenuation range of greater than 60 dB. The intermediate frequency (IF)substitution method using the inductive voltage divider (IVD) operated at several kHz as a reference
standard was selected for the advantageous broadband characteristics. The IVD was adopted for thehigh accuracy and direct traceability to the national standard for a low-frequency voltage ratio. An
attenuation system using the dual channel type of the IF substitution method with the IVD operated at
1 kHz was successfully produced for the frequency range of 10 MHz to 18 GHz. The system is used asa national standard and provides the attenuation calibration to several service systems including Japan
Calibration Service System (JCSS). Improvement to the system was carried out to cover thefrequency range of 18 GHz to 40 GHz. Higher accuracy as well as the system at the low frequency
range was obtained by raising the IF to 10 kHz and employing two seven-decade IVDs in cascadearrangement [Widarta et al, 2007a]. A 10-kHz voltage-ratio standard was also constructed for
uncertainty evaluation of the 10-kHz IF section/receiver of the system [Kawakami et al, 2006]. In
order to increase the degree of automation in the measurement process, an automated receiver wasconstructed using a commercial programmable IVD and an originally designed attenuation constant IF
phase shifter [Widarta et al, 2007b]. Comparison results on attenuation measurements between theautomated and the manual receivers show good agreements. A study on simplifying structure of thesystem, particularly on the RF circuit which might be built in hollow waveguides, was carried out for
implementation to the frequency range of higher than 40 GHz. A single channel type IF substitution
method with the IF phase-locked loop was experimentally constructed and examined at 10 GHz [Iidaet al, 2006a]. Satisfied enough IF signals for operating the IVD reference standard were obtained, even
applying RF signals under the severe conditions. Good performances of the system in the V-band (50GHz to 75 GHz) were also ensured [Iida et al, 2006b]. Some improvements and uncertainties
evaluations to this system are being proceeded now.
In recent years, the development and dissemination of the microwave impedance standards, that are
indispensable for the uncertainty evaluations of the power and attenuation standards in the microwave
frequency region, is strongly required because of a traceability demand of the vector network analyzer
and the input impedance of various test instruments, i.e. EMI receiver, on the basis of various
regulations.
In the year 2004, NMIJ has started to develop the evaluation infrastructure for the microwave
impedance standards on the basis of air dielectric coaxial standard lines, so-call ‘air line’ [Horibe,
2005a]. For next two years, the evaluation systems of the air lines have been established for thevarious types of connectors [Horibe et al., 2004, 2005b]. The calibration services of the complex
voltage reflection coefficients, in the frequency range of 30 kHz to 18 GHz, have been started for PC7
connector in 2005, and for Type-N50 connector in 2006 [Horibe et al., 2006c, d, 2007a]. These
calibration cervices are based on use of the air line as the original impedance standards in the range of
0.5 GHz to 18 GHz, however, the impedance standards are traced to foreign NMI in other frequency
regions. Uncertainty less than 0.0059 for PC7 connector and 0.0069 for Type-N50 connectors wereachieved by using the air lines. Furthermore, the calibration services of the characteristic impedance
derived from the dimensional measurements were started for the air line with PC7 connector in order
to meet the industry’s needs in the traceability issue on the vector network analyzer and impedance
analyzers [Horibe et al., 2005c]. In the year 2006, the three coordinate measuring machine (CMM)
was additionally installed and evaluated for the accurate measurement of the air line’s length as thephase standards [Horibe et al., 2006a, 2007b]. These activities made enhancing the NMIJ’s evaluation
capability of the air line with various connector types, i.e. PC14, PC7, Type-N50, Type-N75, PC3.5,
PC2.92, PC2.4, PC1.85 and PC1.0 (up to 110 GHz). In 2006, the calibration services of the complex
voltage reflection coefficients for PC3.5 connector, in the frequency range of 30 kHz to 33 GHz, have

been started in 2006. Subsequently, in 2007, the scattering parameter (S-parameter) standards havebeen established for PC3.5 connectors in the frequency range of 0.1 GHz to 33 GHz [Horibe et al.,2007a].
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