Edited by Zen-Ichiro Kawasaki and Osamu Fujiwara

E1. Natural Electromagnetic Waves

Subject of commission E can be categorized into two sub-domains, and those are natural and man made electromagnetic (EM) waves. Though there are many considerable sources of natural EM waves, we intended to pay our attention on some special topics to review these three-year's activity related with natural EM waves. The selected topics are the discharge from a thundercloud top to the lower ionosphere, which is well known as "Red sprite", EM wave emission associated with earthquakes, and VHF/UHF radiation due to lightning discharges.

Filed campaigns for observations of Red Sprites and related phenomena were conducted as the international cooperation between Japan - U.S., and Japan - New Zealand. Japanese scientists succeeded to record video pictures of Red Sprites in U. S. and Australia. Tohoku University group discovered interesting phenomena called ELVS, which is the luminosity from the lower ionosphere associated with lightning strikes to the ground. They believe that it is due to a kind of induction filed caused by lightning discharge and abrupt electric field changes. A domestic campaign was also conducted, and the group of Tohoku University successfully recorded many Red Sprites Occurrences by a video camera during winter thunderstorms in 1998. It is well known that the ratio of positive cloud to ground (CG) flashes to negative ones during winter storms is larger than that of summer storms. It is believed that the occurrences of Red Sprites are related with positive CG, and that is why the discovery of existing of Red Sprites during winter storms in Japan is really reasonable and understandable. The group of University of Electro-Communications presented theoretical understanding of Red Sprites and related phenomena.

The EM fields and waves associated with earthquakes have been paid much attention after the terrible Kobe Earthquake, because the EM fields and waves are considered to own the characteristics as the precursor of the occurrence of earthquakes. In other words it is believed that they may be used to forecast the earthquakes. Though the big controversy on the efficiency of EM signals to predict earthquake occurrences is still on going, many evidences from the aspects of the observations have been presented. Groups of University of Electro-Communications and Nagoya Institute of Technology showed enormous progression on this issue independently, and the former group has published related papers, which are shown in the references. To confirm the possibility for the forecasting earthquakes the further investigations are required.

VHF/UHF EM waves associated with lightning discharges have been investigated. One of the purposes of investigations is imaging lightning channels by means of interferometers. The lightning activity inside the cloud can not be seen, and it is important to reveal the feature of discharges inside the thundercloud because it is highly independent on the charge distribution. Charge distribution influences progression sequence on lightning discharges, and the knowledge on the charge distribution will give us the idea how to prevent the lightning hazard. A research group of Osaka University has developed both narrow and broad band interferometers, and published several scientific papers. Their interferometers are on the developing stage.

Followings are the brief review of the activity of the group of the University of Electro-Communications.

A special issue was published on the seismo-electromagnetic phenomena, including seismo-ULF emissions, subionospheric VLF propagation etc. Ultra-low-frequency emissions are found before a big earthquake in Guam in August 1993. The subionospheric propagation was used to find out the precursory signature for the Kobe earthquake of perturbations in the lower ionosphere, by looking at the conspicuous change in the terminator times (minimum in diurnal variation) in the amplitude and phase measurement. The analysis is based on the correlation between the ULF activity and geomagnetic activity and the polarization (Z/H) analysis. A review was made on the electromagnetic phenomena associated with earthquakes. Both the traditional geophysical methods and rather new and promising radio-physical ones are discussed. A new analysis is described for the data from the MASSA active experiments in 1981-83 in USSR, in order to simulate earthquake effects in the magnetosphere and ionosphere using surface chemical explosions. Microfracturing electrification is suggested as a possible mechanism for explaining ULF electromagnetic emissions before and after the earthquakes. ULF emissions observed for the Guam earthquake were re-examined, and they are compared with the theoretical estimations on frequency dependence and intensity of ULF emissions. Precursoty effect in subionospheric VLF propagation found before the Kobe earthquakes has been interpreted in terms of the lowering of the reflection height by a few kilometers.

A new reconstruction method of wave distribution function (direction finding) for magnetospheric VLF/ELF radio waves is proposed by using the statistical regularization. The effect of localized perturbations in the lower ionosphere on subionospheric VLF propagation is studied by means of finite element method, which is an effective even non-Born strong perturbation. The use of unsupervised artificial neural networks is proposed to solve the general ill-posed problems, and are particularly applied it to the estimation of arrival of VLF/ELF radio waves. A powerful VLF generator on board the ACTIVNY satellite produced an effective nonlinear excitation of ion-sound turbulence in the ionosphere. The propagation of very low latitude whistlers has been studied by means of the three-dimensional ray-tracing computations. With taking into account the real magnetic field and realistic density model, it was shown that echo train whistlers could be formed easily by means of non-ducted propagation. The results of ULF/ELF records have shown an increase of the level and variability of the radio signals (vertical field component) in the 1, 3 and 5 Hz bands prior to the earthquake shocks. Three component measurements of nighttime tweek atmospherics have been performed in both northern and southern hemispheres. Multi-mode analysis of the frequency-time structure of tweeks allowed us to study the polarization features. Many case studies for the subionospheric VLF propagation to study the seismic effect, have been carried out, and it is found that the ionospheric perturbation appears as a transient oscillation with a 5- and 10- day period (long-period gravity waves). Propagation of electromagnetic ELF has been studied, in order to identify those Q-bursts and slow-tails are essentially the same phenomenon. Detailed analysis of Trimpis revealed two different regimes in their temporal behavior, and these are discussed by using the scattering problem.

Temporal variations of the global lightning activity were deduced from long-term Schuman resonance continuous data. An analysis is performed of the parameters of nearby lightning discharges. The time domain electric field produced by the model lightning discharges in the neutral atmosphere is computed, and its modification due to geometrical changes of the stroke is examined.

Propagation characteristics of mid-latitude whistlers, especially whistler duct characteristics (duct termination height, enhancement factor etc.), have been investigated based on the ground-based direction finding measurements in Australia and New Zealand. A new type of mid-latitude multi-path whistlers was reported based on the observation in Australia and New Zealand. This new type was found to include a non-ducted whistler.

A general review is made in the progress in the field of extraterrestrial and terrestrial noises, terrestrial and planetary noises, etc. Voyager data are used to estimate the amplitude of Jovian whistlers, and combined use with the ray-tracing computations, enabled us to deduce the information on causative lightning on Jupiter.

Lightning Research Group of Osaka University, (LRGOU) has conducted two main field campaigns. One is a project of the thunderstorm observations in Darwin Austria during developing stage of its monsoon. Objectives of the project are investigation of mechanism and features of thunderstorm activity in Inter Tropical Convection Zone, and understanding characteristics of lightning discharges by means of VHF Broadband Interferometers. LRGOU has designed and manufactured the VHF Broadband antenna with logarithmic amplifier to capture the lightning flash data which occurred in the radius of several tens kilometers, and has realized 3D imaging of development of lightning discharges. That means the time sequence of VHF radiation sources due to discharge developments can be given as visible format in three dimensions. Broadband Interferometers were equipped at two sites with the base line distance of 23.1 km and the GPS was operated to synchronize two interferometers with the time accuracy of one microsecond. A preliminary paper on the broadband interferometers and observations was presented at the international EMC Conference in Zurich in February 1999 and will be published in a Japanese scientific journal in July 1999.

The other campaign is a project of winter storm observations at Hokuriku Coast Japan where they have relatively higher ratio of positive cloud to ground (CG) flashes against to the negative CG flashes than during summer storms. LRGOU operated the narrow band interferometers, slow antenna, and ALPS. The main target of observations is upward initiating lightning discharges from 200 meters stuck. LRGOU succeeded to observe both upward positive leaders and negative leaders by means of interferometers. The lightning currents were measured by shunt resistance by CREIPI and the polarity of leaders can be confirmed. Time sequence of progression of upward positive leaders is presented in terms of UHF radiation sources and is compared with the cross section of C band radar. The leader is propagated toward the region of highest reflectivity (40 dBz) and the temperature of the area is -10 degrees in centigrade. In other wards the direction of leader progression is coincident with negatively charged the area, and LRGOU occluded that positive leader imaging by means of UHF interferometers is achieved. It is noticed that the field campaign was conducted as a cooperation with Tohoku University, Kyoto University, self-defense Academy, Gifu University, Kansai Power Electric Corporation and Hokuriku Power Electric Corporation. Tohoku University succeeded to take video pictures of red sprites and ELVS during winter storms. The confirmation from the aspects of science is undergoing. LRGOU is working for TRMM/LIS evaluation through ground base measurement.

Both rocket and laser triggered lightning experiment in the field have been conducted eagerly, and excellent development has achieved. It is noticed that the first success of laser triggered lightning in the field was accomplished on February 11, 1997.

Though we summarized this three-year activity in the field of commission E for special subjects, there are various scientific papers by Japanese scientists in both international and domestic journals. The publication list is given as the references at the end of this report.

The activity related with Manmade Electromagnetic Waves are reviewed as following:

E2. Noise Sources

A direct lightning strike against telecommunication buildings induces voltages on bus cables of switching equipment. These induced voltages were investigated experimentally [Sato et al., 1998]. The occurrence probability of estimated lightning surge current at a lightning rod was derived before and after installing a dissipation array system (DAS) [Kuwabara et al., 1998].

Concerning electrostatic discharge (ESD), an analytical approach to model the indirect effect caused by ESD was proposed [Fujiwara, 1996]. An approach to a spark resistance formula was also investigated [Kang et al., 1997]. The Levels of transient electromagnetic fields caused by the spark discharge between charged metal spheres were estimated numerically and experimentally [Fujiwara and Hori, 1998a; Fujiwara et al., 1998b]. In addition, by using an electromagnetic field theory, charged floor potential was analyzed [Fujiwara et al.,1997a]. The electrical properties of shoes determining charged human body potential were also measured [Fujiwara and Takeshita, 1997b]. Based on ground potential variations, ESD immunity of electronic equipment was studied [Mori and Shinozaki, 1996]. To improve the reproducibility of ESD current of tester, fluctuations in the discharge current caused by various test conditions were analyzed [Murota, 1996].

Concerning noises due to discharge, the relation between showering noise waveform and the cathodic contact surface variation was clarified [Nitta et al., 1996]. The charge neutralized at a small gap discharge was evaluated from measured electromagnetic fields [Ishigami and Iwasaki, 1996a], and the coupling to transmission lines of radiation of the small gap discharge was estimated from measured discharge current [Ishigami and Iwasaki, 1996b]. In addition, an experimental investigation was conducted to evaluate noise characteristics of surface discharge combustion flue gas cleaning systems [Uchimura, 1996].

Statistical distributions of automotive radio noises in Tokyo were measured by using a noise waveform analyzer in frequency bands of 1 - 3 GHz. Variation of the impulse height can be expressed as a log-normal distribution, and impulse emission seems to be Poisson-distributed in time [Yamanaka and Sugiura, 1997].

E3. Composite Noise

A simulation model of composite noise was proposed based on the combination of Gaussian noises. The model was called composite noise generator (CNG) and was shown to be good fit to the real characteristics of both noises from breaking arcs and DC motors [Inoue, 1996].

E4. Effect of Noise on System Performance

Concerning immunity test methods for telecommunications equipment, several efforts have been done by NTT (Nippon Telegraph and Telephone Co.). Changes to a radiated RF-field immunity test method was proposed in order to obtain a better measure for acoustic noise in telephones [Tokuda et al., 1996]. Immunity test facility for telecommunications equipment above 1 GHz was evaluated experimentally [Tajima et al., 1996a]. A new method for evaluating the image quality of facsimile output was proposed in order to reduce evaluation time and cost [Hiroshima et al., 1998]. New coupling and decoupling networks were developed below 150 kHz [Kuwabara and Hiroshima, 1997]. Site attenuation measurements using shortened dipole antennas were conducted in order to evaluate anechoic chamber for CISPR emission measurement [Maeda et al., 1996a]

Concerning wireless communications, the impact of noises from microwave oven on communication systems was investigated experimentally. The bit error rate degradation of a typical PHS receiver was observed and found not to exceed 0.001 [Yamanaka and Shinozuka, 1996], and the performances of PDC and ISM band wireless LAN systems were evaluated by computer simulations based on the measured results [Miyamoto et al., 1996]. Moreover, the interference characteristics between 2.4 GHz ISM-band wireless LANs have been evaluated experimentally and theoretically [Takaya et al., 1998]. Microwave propagation characteristics and performance of wireless communications for indoor environments have been investigated [Maeda et al., 1998].

E5. Measuring System and Location of Noise Sources

For the electric field sensor using LiNbO3 optical modulator developed by Kuwabara, the improvement and evaluation of its characteristics have been conducted experimentally and theoretically. Sensitivity of the sensor was analyzed theoretically by using the method of moment [Kobayashi et al., 1996]. The sensor was developed to have a very small resistive element (10 mm length), which can be used up to 9 GHz [Tajima et al., 1996b]. Moreover, an optical bias angle control method of the sensor using mechanical stress was investigated experimentally [Kobayashi et al., 1998].

A small sensing device, which has equivalent characteristics to the absorbing clamp method, was developed for EMI measurement [Koizumi et al., 1996]. This device can be applied to the inspection apparatus for products such as power tools to examine the conformance to EMI regulations.

A new method for finding emission sources was proposed based on the discrete singularity technique, which was able to find out emission sources without phase data [Murakawa et al., 1996]. The applicability of a new method by utilizing CISPR emission measurement system has also been investigated [Ishida et al., 1998].

Superposition characteristics of the radiated emission from telecommunications equipment [Takahashi et al., 1996] and distribution characteristics of the unwanted emission around a building [Maeda, 1996b] were investigated experimentally and theoretically. A new searching method of grounding route in buildings was developed using amplitude and phase [Kuramoto et al., 1997].

E6. Noise Radiation and Coupling to Lines

For twisted pair cables, the characteristics of emission from them were derived in high speed LAN applications [Kuwabara et al., 1996]. Noise currents and noise voltages in AC supply line due to a fluorescent lamp switching were investigated on their induced mechanism [Shimoshio et al., 1996]. In addition, a calculation method was given for a balanced cable with partial unbalance at arbitrary position [Shimoshio et al., 1998a]. An effective countermeasure was proposed for suppressing common mode noise in balanced pair lines with common mode choke [Shimoshio et al., 1998b]. Furthermore, a method for determining the transmission direction of common-mode noise was proposed by measuring its energy flow [Kobayashi et al., 1997].

Concerning the radiated emission from printed circuit boards (PCB), the mechanism of radiated emissions from multilayer PCBs was investigated using a time-domain magnetic field measurement [Harada et al., 1997]. A prediction of far-field EMI by near-field measurements was proposed [Tobana and Kami, 1996, Torigoe et al., 1997], and the EMI spectra emitted from a signal line on a digital PCB were modeled [Miyashita et al., 1996].

A ferrite core attached to a coaxial cable was analyzed to evaluate the effect in reducing the normal-mode noise [Fujiwara and Ichikawa, 1996; Ichikawa et al., 1998]. A theoretical equation for reduction effect of the normal-model noise by ferrite core attachment was derived.

On EMC problems of intra/inter systems, coupling phenomena in microstrip systems were treated and a simplified analyzing method was proposed, which could well explain an extra-ordinal response. Pulse waveforms propagating in and on a coaxial cable were also analyzed by empirical ways, which explained laying emphasis on the pulse oozing mechanism [Echigo et al., 1997a, 1997b].

The crosstalk between non-parallel transmission lines was analyzed by using a circuit concept [Liu and Kami, 1996, 1997]. A theory based on combined differential and common-mode propagation was presented for crosstalk and transient analysis of pairs of asymmetric coupled interconnects [Omid et al., 1997c]. In addition, the coupling responses of an external transient electromagnetic field to a transmission line were analyzed [Kami and Kimura, 1996]. The derived line equations were verified by experiments. Furthermore, time-domain and frequency-domain responses were analyzed for both uniform and non-uniform transmission lines excited by external electromagnetic fields [Omid et al., 1997a, 1997b, 1997d, 1998]. The externally excited uniform transmission lines permit closed-form solutions in terms of inverse chain matrix, whereas the non-uniform transmission lines can be treated by a method of equivalent cascaded network chain.


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Echigo, H. and R.Sato [1997a],"Pulse leakage phenomena during the propagation on the inside and outside of a coaxial cable as a model of intra/inter system EMI," IEICE Trans. Commun., vlo.E80-B, 11, pp.1625-1632

Echigo, H., M.Nakajima and R.Sato [1997b], "An extreamly simplified calculation method for the transients in a coupled micro-strip line by phenomenological modeling," Proc. of 1997 IEEE Instrumentation & Measurement Technology Conference

Fujii, K., S. Ishigami and T. Iwasaki [1996], "Evaluation of complex antenna factor of dipole antenna by the near-field 3-antenna method with the method of moment", Trans. IEICE, vol.J79-B-II, pp.754-763

Fujiwara, O. [1996a], "An analytical approach to model indirect effect caused by electrostatic discharge," IEICE Trans. Commun., vol. E79-B, 4, pp. 483-489

Fujiwara, O. and T. Ichikawa [1996b], "An analysis of load effects produced by ferrite core attachment," Trans. IEICE, vol. J79-B-II, 11, pp. 950-955

Fujiwara, O., K. Nakazawa and H. Takeshita [1997a], "An analysis of charged floor potential using electromagnetic field theory," Trans. IEICE, vol. J80-B-II, 9, pp. 784-790

Fujiwara, O. and H. Takeshita [1997b], "Measurement of electrical properties of shoes determining charged human body potential," Trans. IEE of Japan, vol. J117-A, 12, pp. 1165-1169

Fujiwara, O. and T. Hori [1998a], "Level estimation of transient electromagnetic fields caused by spark discharge between charged metal spheres," Trans. IEE of Japan, vol. 118-c, 1, pp. 9-14

Fujiwara, O., K. Kawaguchi and N. Kurachi [1998b], "FDTD computation modeling for electromagnetic fields generated by spark between charged metals," Proc. of Int. Symp. on Electromagn. Compat., Wroclaw, Poland, pp. 268-271

Furukawa, H., S. Uchida, Y. Shimada, H. Yasuda, C. Yamanaka, Z-I Kawasaki, T. Yamanaka and Y. Ishikubo [1996], "Study of laser triggered lightning by simulation -Simulation on start-up of discharges from discontinuous plasmas-" , The Review of Laser Engineering, 24, 5, pp. 590-595

Galperin, Yu. I. and M. Hayakawa [1996], "On the magnetospheric effects of experimental ground explosions observed from AUREOL-3," J. Geomag. Geoelectr., vol.48, pp.1241-1263

Harada, T., H. Sasaki and Y. Kami [1997], "Investigation on radiated emission characteristics of multilayer printed circuit boards", IEICE Trans. Commun., vol.E80-B, pp.1645-1650

Hayakawa, M. [1996a], "Seismo-electromagnetic phenomena," in M. Hayakawa (ed.), Special Issue, Tokyo, J. Atmos. Electricity, vol.16, No.3, pp.161-288

Hayakawa, M.[1996b], "VLF subionospheric propagation as a method of short-term earthquake prediction," J. Atmos. Electr., vol.16, pp.19-28

Hayakawa, M., R. Kawate, O. A. Molchanov and K. Yumoto [1996c], "Results of Ultra-low-frequency magnetic field measurements during the Guam earthquake of 8 August 1993," Geophys. Res. Lett., vol.23, pp.241-244

Hayakawa, M., O. A. Molchanov, T. Ondoh and E. Kawai [1996d], "The precursory signature effect of the Kobe earthquake on VLF subionospheric signals," J. Comm. Res. Lab., vol.43, pp.169-180

Hayakawa, M., O. A. Molchanov, T. Ondoh and E. Kawai [1996e], "Anomaliesin the sub-ionospheric VLF signals for the 1995 Hyogo-ken Nanbu earthquake," J. Phys. Earth, vol.44, pp.413-418

Hayakawa, M., R. Kawate and O. A. Molchanov [1996f], "Ultra-low frequency signatures of the Guam earthquake on 8 August 1993 and their implication," J. Atmos. Electr., vol.16, pp.193-198

Hayakawa, M., O. A. Molchanov, T. Ondoh and E. Kawai [1996g], "Precursory signature of the Kobe earthquake on VLF subionospheric signal," J. Atmos. Electr., vol.16, pp.247-257

Hayakawa, M. [1997], "Electromagnetic precursors of earthquakes: Review of recent activities," in W. Ross Stone (ed.), Rev. Radio Sci. 1993-1996, London, Oxford Univ. Press, pp.807-818

Hidayat, S. and M. Ishii [1996a], "Error in lightning location by time-difference and direction (TDD) technique - Theory", Trans. of I. E. E. of Japan, vol. 116-B, 4, pp. 410-416

Hidayat, S., M. Ishii, J. Hojo, K. T. Sirait and P. Pakpahan [1996b], "Observation of lightning in indonesia by magnetic direction-finder network", Proc. 10th ICAE, Osaka, pp.468-471

Hidayat, S. and M. Ishii [1998], "Spatial and temporal distribution of lightning activity around Java", J. Geophys. Res., vol. 103, D12, pp. 14001-14009

Hirari, M. and M. Hayakawa [1996a], "A bayesian regularization approach to ill-posed problems with application to the direction finding of VLF/ELF radio waves," IEICE., Trans. Commun., vol.E79-B, pp.63-69

Hirari, M. and M. Hayakawa [1996b], "A neural network for the DOA of VLF/ELF radio waves," IEICE Trans. Commun., vol.E79-B, pp.1598-1605

Hiroshima, Y., N. Kuwabara, S. Tominaga and R. Okayasu [1998], "Method of calculating facsimile image quality of immunity testing", 14th International Wroctaw Symposium on EMC, Wroctaw, pp.517-521

Honma, N., F. Suzuki, M. Ishii and S. Hidayat [1996], "Influence of geography on location accuracy of direction finder network", Proc. 10th ICAE, Osaka, pp.309-312

Honma, N., F. Suzuki, Y. Miyake, M. Ishii and S. Hidayat [1998], "Propagation effect on field waveforms in relation to time-of-arrival technique in lightning location", J. Geophys. Res., vol. 103, D12, pp. 14141-14145

Hobara, Y. and M. Hayakawa [1997a], "Ducted propagation of lightning generated Whistlers in The Jovian magnetosphere," J. Atmos. Electr., vol.17, pp.33-45

Hobara, Y., S. Kanemaru, M. Hayakawa and D.A.Gurnett [1997b], "On estimating the amplitude of Jovian Whistlers observed by Voyager 1 and implications concerning lightning," J.Geophys.Res., vol.102, pp.7115-7125

Hobara, Y., V. Y. Trakhtengerts, A. G. Demekhov, and M. Hayakawa [1998], "Cyclotron amplification of whistler waves by electron beams in an inhomogeneous magnetic field," J. Geopys. Res., vol.103, pp.20449-20458

Hussein, A. M., W. Janischewskyj, J-S. Chang, V. Shostak, W.A. Chisholm, P. Dzurevych and Z-I. Kawasaki [1995], "Simultaneous measurement of lightning parameters for strokes to the Toronto Canadian National Tower" J. of Geophysical Research, 100, D5, pp.8853-8861.

Ichikawa, T., H. Kawada and O. Fujiwara [1998], "An analysis of normal-mode noise caused by braided shield current flowing on coaxial cable attached by a ferrite core," Trans. IEICE, vol. J81-B-II, 4, pp. 327-335

Inoue, H. [1996], "Induced noise from arc discharge and its simulation", IEICE Trans. Commun., vol.E79-B, pp.462-467

Ishida, Y., K. Murakawa, K. Yamashita and M. Tokuda [1998], "New finding method of radiated emission sources utilizing CISPR emission measurement system," International Symposium on Electromagnetic Compatibility, Rome

Ishigami, S. and T. Iwasaki [1996a], "Evaluation of charge transition in a small gap discharge", IEICE Trans. Commun., vol.E79-B, pp.474-482

Ishigami, S. and T. Iwasaki [1996b], Output voltage of transmission line coupled with far-field radiation of small gap discharge", Trans. IEICE, vol.J79-B-II, pp.771-779

Ishii, M., J. Hojo, K. Shimizu, H. Saotome and T. Kadoya [1996a], "Location of sources of electromagnetic radiation for lightning discharges in winter", Proc. 10th ICAE, Osaka, pp. 592-595

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Ishii, M., K. Shimizu, J. Hojo and K. Shinjo [1998], "Termination of multiple-stroke flashes observed by electromagnetic field", Proc. 24th Int. Conf. On Lightning Protection, Birmingham, pp. 11-16

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J. Onuki., Z-I. Kawasaki, M. Wada, K. Matsu-ura, T. Matsui and M. Adachi [1996], "Imaging of lightning channel in three dimensions using interferometer" , T. IEE Japan, 116-B, 4, pp. 475-481

Kami, Y. and M. Kimura [1996], "Coupling of a transient near field to a transmission line", IEICE Trans. Commun., vol.E79-B, pp.497-514

Kang, I.-H., O. Fujiwara and J. Wang [1997], "Analytical approach to the spark resistance formula caused by electrostatic discharge," Electron. Lett., vol. 33, 14, pp. 1203-1204

Katagiri, S., K-I. Morita, N. Kawaguchi and M. Hayakawa [1997], "An imaging algorithm using the bispectrum in radio interferometry," Pub. Astron. Soc. Japan, vol.49, pp.123-129

Kawasaki Z-I. [1998], "Lightning activity in Darwin and LIS observations" , 32nd Scientific Assembly of COSPAR, Nagoya, July, pp. 12-19

Kawate, R., O. A. Molchanov and M. Hayakawa [1998], "Ultra-low-frequency magnetic fields during the Guam earthquake of 8 August 1993 and their interpretation," Phys. Earth Planet. Inter., 105, pp.239-248

Kikuchi, H., Z-I.Kawasaki and M. Hayakawa [1997], "Terrestrial and planetary EM noise," in W. Ross Stone (ed.), Rev. Radio Sci. 1993-1996, London, Oxford Univ. Press, pp.397-418

Kobayashi, R., K. Tajima, N. Kuwabara and M. Tokuda [1996], "Theoretical analysis of the sensitivity on electric field sensor using LiNbO3 optical modulator," The Trans. of the IEICE B- Vol. J79-B- 11, pp.734-743

Kobayashi, R., N. Kuwabara, and M. Hattori [1997], "A method for determining the transmission direction of common-mode electromagnetic noise by measuring its energy flow",12th Inter. Zurich Symposium on EMC, Zurich, pp.210-206

Kobayashi, R., K. Tajima, N. Kuwabara, and M. Tokuda [1998a], "Optical bias angle control method for electric field sensor using Mach-Zehnder Interferometer", The Trans. of the IEICE B-II, J81-B-II, 5, pp.542-549

Kobayashi, R., K. Tajima, N. Kuwabara, and M. Tokuda [1998b], "Improvement of frequency characteristics of electric field sensor using Mach-Zehnder Interferometer", The Trans. of the IEICE B-II, J81-B-II, 7, pp.699-706

Kogure, H., H. Nakano, K. Koshiji and E. Shu [1997], Analysis of electromagnetic field inside equipment housing with an aperture", IEICE Trans. Commun., vol.E80-B, pp.1620-1624

Koizumi, T., K. Takahashi, S. Suzuki, H. Sone and Y. Nemoto [1996], Sensing device for in-line EMI checker of small electric appliances", IEICE Trans. Commun., vol.E79-B, pp.509-514

Kuramaoto, S., M. Hattori, and T. Ideguchi [1997], "Searching method of grounding route in buildings using amplitude and phase", 1997 IEEE International Symposium on EMC, Dallas, pp.149-153

Kuwabara, N, T. Tominaga, M. Kanazawa, and S. Kuramoto [1998], "Probability occurrence of estimated lightning surge current at lightning rod before and after installing dissipation array system (DAS)", IEEE 1998 International Symposium on EMC, Denver, pp.1072-1077

Kuwabara, N. [1995], "EMC measurement method for telecommunication line ports", ISCOM '95, Taipei, pp.753-760

Kuwabara, N., H. Makino, K. Tajima and M. Tokuda [1996], "Characteristics of emission from twisted pair cable used for high speed LANs," 13th International Wroclow Symposium, Wroclow

Kuwabara, N. and Y. Hiroshima [1997], "Development of coupling and decoupling networks below 150kHz", 1997 International Symposium on EMC, Beijing, pp.17-20

Lee, J., Z-I. Kawasaki, K. Matsu-ura and T. Matsui [1997], "The characteristic of winter thunderclouds on the coast of the Hokuriku district according to the observation of generation of lightning", Tenki 44, 11, pp. 47-50

Lee, J., M. Wada, Z-I. Kawasaki, K. Matsu-ura, M. Takeuchi and Y. Sonoi [1998], "Lightning activity during winter thunderstorm season observed by SAFIR", T. IEE Japan, 118-B, 7/8, pp. 811-817

Liu, W. and Y. Kami [1996], "Analysis of crosstalk between non-parallel transmission lines by using a circuit concept", Trans. IEICE, vol.J79-B-II, 11, pp.819-826

Liu, W. and Y. Kami [1997], "Time domain coupling between non-parallel transmission lines", IEICE Trans. Commun., vol.E80-B, pp.1639-1644

Maeda, A., A. Sugiura, N. Kuwabara, and S. Usuda [1996],"Site attenuation measurements using shortened dipole antennas", The Trans. of the IEICE B-II, J79-B-II, 11, pp.764-770

Maeda, Y., Y. Komatsu and M. Hattori [1996], "Distribution characteristics of unwanted emission around a building," The Trans. of the IEICE B- Vol. J79-B- 11, pp.845-853

Maeda, Y., K. Takaya, and N. Kuwabara [1998], "Microwave propagation characteristics and performance of wireless communications for indoor environments", EMC'98 Roma International Symposium on Electromagnetic Compatibility, Roma, pp.821-826

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