Search

As a remedy to multipath fading in land mobile communication, adaptive antenna arrays combined with equalizers have been proposed. For hardware realization and adaptive algorithm development in order to alleviate fading by temporal and spatial processing, it is necessary to clarify the spatiotemporal characteristics of the propagation channel such as the delay time and direction of arrival of multipath waves. In a microcell using a low antenna-height base station, the spatiotemporal propagation characteristics are measured for line-of-sight and non-line-of-sight propagation at 3.35 GHz. Characteristics of these channels have been presented. With regard to non-line-of-sight propagation, the measured spatiotemporal characteristics are modeled and the angular spread and the delay spread of the arriving waves are quantitatively evaluated. Also, when the transmission characteristics of fading prevention techniques by spatiotemporal processing are evaluated by computer simulation, an example of the delay-azimuth profiles that is usable as a reference for setting the conditions for fading is presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(7): 11–21, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10032 [ABSTRACT FROM AUTHOR]

The measured results and the results of analysis by the ray tracing method in a real tunnel are compared. The propagation characteristics considering the radiation pattern of an antenna placed inside the tunnel are estimated. By comparison of the measured and analyzed results, the effectiveness and validity of the ray tracing method are shown. The propagation loss and fading in the tunnel are discussed. Further, the propagation characteristic is estimated by considering the radiation pattern of the base station antenna for the tunnel booster system. The analysis demonstrates that the dual radiation pattern is effective for the base station antenna. The variation of the covered area when the radiation pattern is varied is studied. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 84(4): 1–10, 2001 [ABSTRACT FROM AUTHOR]

In parabolic antennas with a defocused primary radiator, performance degradation, such as gain degradation and increased sidelobe levels, arises due to aberration in the aperture. In this paper, the aberration produced in the aperture is determined by beam mode expansion, and it is shown that various aberrations can be represented by simple expressions by considering the dominant beam mode. Using the derived expression for the aberrations, a formula for the beam deflection characteristics is derived for the co-polarization component by the aperture distribution method. A simple expression is derived for the gain degradation under the condition that F/D is large and the edge level is low. The result obtained by the proposed method is compared by numerical examples to that of the strict current distribution method, and the validity of the proposed method is demonstrated. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(9): 39–50, 1999 [ABSTRACT FROM AUTHOR]

Recently, the downsizing of portable radio equipment has been progressing, and wristwatch portable radio equipment is now available. The antenna for such equipment is highly affected by the human body, but a slot antenna can positively utilize the body effect. This paper proposes a small slot antenna installed in the band of a wristwatch-type pager. The radiation characteristics were measured and calculated for cylindrical and flat shapes. The peak gain was –13 dBd for a cylindrical slot antenna (peak gain for a flat slot was –22 dBd). The effect of curvature of the cylindrical antenna element was also studied. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(9): 30–38, 1999 [ABSTRACT FROM AUTHOR]

In a low-antenna-height line-of-sight (LOS) microcell, the delay spread characteristic strongly depends on the road shape, the location of the transmitting and receiving points, and so on. To analyze this propagation mechanism, it is necessary to deal with location-specific properties. This paper describes analyzed results for the multipath delay mechanism in a rectilinear street with intersections where both transmitting and receiving stations exist. Special focus is placed on reflection at LOS building walls and on diffraction at building corners at street intersections, and their effect as a factor creating multipath delay is investigated numerically. We show that waves created by their reflection and/or diffraction are significant multipath delays making a major contribution to delay spread in microcells. This paper also presents a comparison between the calculated and measured delay spread, and discusses the effectiveness of the propagation mechanism described. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(4): 56–70, 1999 [ABSTRACT FROM AUTHOR]

In the area of mobile communications, there has been increasing demand and development for new technologies and services such as digitalization and personalization. With this as background, this paper studies the use of adaptive antenna technology for mobile communication. In the area of mobile communications, the adaptive antenna technology has been studied with a view to reducing the fading for reception by the mobile station. In the case of microcells and indoor communication for which an expanded use is anticipated, arrivals of multiple waves tram various directions are expected even for the base station so that the application of the adaptive antennas to the base stations is effective. In the case of high-speed data transmission such as wireless local wireless networks (LAN), further reduction of fading and interference is required. Also, the frequency sharing among different radio services is an area in which the adaptive antenna is useful. Introductions of dynamic control of the systems are expected for mobile communications in time, space, and frequency domains. The adaptive antenna is effective for control in space. The dynamic zone configuration will he a new application area in which, depending on the distributions of the users, the zone shape is varied. [ABSTRACT FROM AUTHOR]

This paper describes the results of the radio propagation experiment between an aircraft or a ship and a ground earth station by means of the Engineering Test Satellite V (ETS-V) as a part of the navigation experiment program which is aimed at developing the technology for utilizing a satellite for navigation assistance by a ship and for control of an aircraft of the ocean. First, the antenna on a moving vehicle is summarized. Next, the experimental results with each moving vehicle are described with regard to the magnitude and the periodicity of the received signal level. The results were analyzed and the cause of the level variation was found in some cases. The magnitude of the variation of the signal level (fading range) was about 6 dB at the maximum for the elevation angle of the satellite from 45° to less than 10° in the case of the experiment with an aircraft. In the case of a ship, the magnitude increased with a decreasing satellite elevation angle. In the case of a one-element antenna with a gain of 6 dBi, the magnitude of variation was more than 10 dB at an elevation angle of 10°. The periodicity of the variation was investigated by deriving the frequency components by means of the Fourier transform. In most cases for an aircraft, no remarkable frequency characteristic was observed and the spectrum was flat at the frequency range of less than 25 Hz. On the other hand, in the case of a ship, the components less than 1 Hz are predominant at a low satellite elevation angle. Hence, it is clear that the nature of the reflection is different in the aircraft and the ship. For the latter, the reflection from the ocean surface is predominant. [ABSTRACT FROM AUTHOR]