[in Japanese]

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In additional to transmitting power, distribution power lines are used as communication media for controlling distant switches, load management, meter reading and so on. In this communication, a ripple control (RC) system has been used in remote areas as usual. Nowadays the RC system has been replaced by a chirp signal system, which is one of spread-spectram (SS) systems, in this communication in Kyushu area. Transmission speed and reliability of this communication are improved by this system. In this paper, we discuss a background of a distribution power line and the SS-chirp signal system on this line.

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This paper is concerned with the finite-difference and time-domain (FDTD) analysis of electr magnetic wave propagation in a tunnel. The tunnel wall is considered to be a lossy dielectric which is a goo model of concrete. Excitation is made by a line source in the tunnel and the conventional FDTD method applied to calculate electromagnetic fields both in the tunnel and in the tunnel walls. A time dornain modelin of the surface impedance boundary is proposed to limit the domain where fields are computed. The tunn structure is assumed to be two-dimensional, and analyses are carried out both for TM and TE wave excitation Numerical results show that the surface impedance calculated by the FDTD method approximately agress wit that given by the conventional spectral domain method.

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The GTD treats electromagnetic fields as rays of light and represents the total fields as the sum of the direct, reflected and diffracted fields. This paper reports that the compornents of the direct and diffracted fields are confirmed through measuring the forward scattering fields by a strip.

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The Differential GPS is known as the effective method that increases the positioning accuracy. This accuracy is achieved by using information for correcting and offsetting errors. In the positioning at two points of no great distance, selecting the same satellite combination at each point, it must make no significant difference in error. In this paper, we present and discuss a simplified differential GPS method for the distance measurement with a GPS receiver. From the result of our experiments, fairly good accuracy of distance measurement is obtained.

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The positioning by using the C/A code of GPS is not always accurate enough in practical usage because of SA (Selectable Availability). We study new accurate positioning by a GPS receiver. This paper presents two methods for improving positioning accuracy. One is the positioning by averaging, by which we can obtain good accuracy of meter level. The other is by using vertical error, it also improves the accuracy. Furthermore, we discuss vertical positoning, but no relationship between VDOP and vertical error is found from the result of measurements.

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Transmission line loss of strip line of receiving antenna for the satellite TV composed of flat antenna (TDLA) with plane reflector is a cause of reduction of total gain. It is reported effective to load a dielectric material in front of antenna element, in order to improve the gain of antenna. In this paper, gain characteristics of several type of dielectric load for the twin delta loop antenna with refrector is investigated experimentally.

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In Personal Handyphone System (PHS), it is desired that an antenna of base station using on crossing road has an orthogonal radiation pattern. This paper describes a design of antenna array with orthogonal radiation pattern, which is hard to be affected by error in space of antenna elements.

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For the effective use of the frequency band and the design of a mobile communication system, it is essential to understand the propagation characteristics, such as the field-strength and the delay spread, in its service area, especially in urban areas. This paper describes a method for calculating delays of multi-path signals in a built-up area, which are necessary to estimate the delay spread.

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In order to utilize the higher frequency band such as at 21 GHz for the Satellite Broadcasting, it is necessary to overcome the heavy rain attenuation in that band. This paper deals with interference between beams of a multi-beam transmitting antenna on board which is included in a remedy system for the rain attenuation, in which power distribution to the beams is variable and higher power is divided to beams in higher attenuation.

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The elliptical microstrip antenna is theoretically analyzed by the cavity model with the surface admittance. In the cavity model, the antenna is treated as a resonant cavity bounded above and below by the conducting plates and on the side by the admittance wall. The surface admittance is calculated by the spectral domain analysis. The electromagnetic fields within the cavity are expanded in terms of the eigenfunctions in the cylindrical coordinate system and determined by applying the method of least-square to the impedance boundary condition at the side aperture.

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A rectangular loop antenna integrated with GaAs FET for mobile communication receiver is experimentally analyzed. A rectangular conducting plate is inserted within the loop. A coplanar waveguide (CPW) is used as a transmission line. The GaAs FET FHC30LG is integrated between the feed point of loop and the CPW. The input impedance, the receiving pattern and the actual gain are measured as a function of size of conducting plate at frequency of 280MHz.

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An active loop antenna for television receiver is presented and its broadband operation is reported. This antenna is fabricated on a thin dielectric film by using the photoetching techniques. A coplanar waveguide (CPW) is printed as a transmission line on the film. The GaAs FET FHC30LG is integrated between the feed point of loop and the CPW. Actual gains more than 9dBd (relative values to the halfwave dipole antenna) are obtained at the frequencies for television channels 4-12 from 170 to 222MHz and channels 13-62 from 470-770MHz in Japan.

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