Hajime Fukuchi

Centimeter wave propagation experiments using the beacon signals of CS and BSE satellites

The wave propagation experiments using Japanese geostationary satellites CS (20/30 GHz) and BSE (12/14 GHz) satellites have been performed at the Kashima earth station of the Radio Research Laboratories (RRL). Cumulative rain attenuation and cross-polarization discrimination (XPD) statistics are given for the period of three years at 11.7 GHz (vertical polarization) and for the period of four years at 19.5 GHz (circular polarization). It is shown that the yearly rainfall rate and attenuation distributions are well approximated by log-normal distributions, and the XPD distribution is well approximated by a normal distribution. Monthly and time-of-day variation of the attenuation and XPD distributions are presented. Duration statistics of attenuation and XPD are presented and characterized. Other characteristics in the wave propagation, such as effective path length, frequency dependence of attenuation, and joint statistics of attenuation and XPD are derived and discussed. Rainfall events are classified into three rainfall types, stratus, cumulus, and others using measurements of the radar reflectivity factor along the satellite-to-earth path, and the dependence of XPD characteristics on the rainfall type is also presented and discussed. Some prediction methods of calculating attenuation and XPD statistics are applied to the data obtained in these experiments and the predicted results are compared with the measured ones. It is found that some corrections are needed when the XPD statistics are predicted from the attenuation statistics using the theoretical relation between XPD and attenuation.

Up-Link Power Control Experiment

This paper presents the result of an up-link power control experiment conducted by using BSE. The result shows that the variation of up-link receiving power due to rain attenuation was kept within 0.5 dB in rms and 1.5 dB in peak in most of time by a simple method, where the attenuation of the up-link receiving power was estimated from receiving power of a down-link signal. Effect of up-link power control on cross polarization interference will be also briefly discussed.

Time Diversity Method Evaluated by Rainfall Rate in Tropical Asian Region

[Abstra ct] As an example of novel rain attenuation mitigation technologies categorized in the diversity methods , we analyzed a macroscopic time diversity method. This method makes use of the natural characteristics that rain never lasts forever. In th is time di versity method, a part or whole information is transmitted several times with a certain delay between transmissions . The receiver saves the several versions of the information in the memory and these versions are used complementarily. In order to evaluate the time diversity effect quantitative ly such as diversity gain which is applicable to all over Asian region especially in tropical one where many large rain -induced attenuation events are expected. For this purpose, we use AMeDAS rainfall data which is available all over Japan and rainfall data measured in Indonesia, tropical Asian region . We show the effect of time diversity and also compare time diversity gain s observed in Japan and Indonesia.

Worst month statistics of attenuation and XPD on Earth-space path

Using the attenuation and cross-polarization discrimination (XPD) statistics measured in the CS (20/30 GHz) and BSE (12/14 GHz) centimeter wave propagation experiments performed for over four and three years, the worst month statistics of attenuation and those of XPD on earth-space path at 11.7 and 19.5 GHz are derived. The probability relation between the annual and worst month statistics is approximated by a power-law relation, and the constants for the relation are derived by a least squares procedure. It is found that the relation is independent of both frequency and polarization. The cumulative probability ratios of the worst month to annual statistics at the same attenuation or XPD values are derived as a function of annual cumulative probability. The ratios are well described by the Brussaard model of the worst month statistics. Attenuation ratio and XPD difference among the annual and worst month statistics are also derived and compared with the predicted results.

Statistics of Rain Attenuation and other Environmental Effects Associated with the BSE Satellite Down-Link at 12 GHz in Japan

Propagation measurements were carried out at 12 GHz on the down-link of the Japans Medium-scale Broadcasting Satellite for Experimental Purpose (BSE), launched in 1978. Analyses of the measurements have revealed the statistics of rain attenuation and duration of fade at 12 GHz in various parts and climates of Japan, as well as other environmental effects such as degradation of reception quality due to snowfall on receiving antennae, reduction in carrier-to-noise ratio by solar noise interference and diffraction attenuation by obstacles. This paper describes the results which are useful for planning and operation of satellite broadcasting systems.

Diversity Effects in Satellite-Ground Laser Communications Using Satellite Images

The sites selection of optical ground stations (OGSs) in satellite-ground laser communications and the effects applied two types of diversity schemes are examined quantitatively. The existence of interception of the laser beam by clouds, which causes communication quality degradation is judged using the dot values of meteorological satellite images. The proposed sites are chosen in consideration of the locality of clouds distribution, and the existing terrestrial networks. Siteand time-diversity are applied to the proposed sites, and the achievement scheme of not less than 99.9% availability is examined.

Advanced satellite broadcasting experiment using Japan's R&D satellite COMETS

The Communications Research Laboratory (CRL) and the National Space Development Agency of Japan (NASDA) have been studying an advanced satellite broadcasting system that uses the K-band such as 21 GHz band. This study has evolved into an experimental satellite project called COMETS (Communications and Broadcasting Engineering Test Satellite), which will be launched in 1997. The performance of the components, such as the high-power TWTA and multi-beam antenna, and planned experiments are described.

Satellite borne multibeam antenna for 21 GHz band regional satellite broadcasting

The Communications Research Laboratory (CRL) and the National Space Development Agency of Japan (NASDA) have been studying an advanced satellite broadcasting system that uses 21GHz band which was allocated in WARC-92 as the band for studio quality HDTV satellite broadcasting. Regarding this study, CRL and Toshiba corp. have developed a breadboard model (BBM) of the satellite borne 27/21 GHz band multibeam antenna as a key satellite component for future regional satellite broadcasting system. This paper describes the antenna configuration and the results of designing and measurements.

Broadcasting Technologies for Effective Utilization of the Radio Spectrum.

近年, 通信・放送分野のみならず, 電波測位・航法, リモートセンシング, 産業等, 多くの分野での電波利用が進み, 周波数の有効利用がますます重要となっている.放送分野では, その技術の歴史が, 周波数有効利用技術の歴史ともいえる.ここでは放送分野での周波数有効利用の例を紹介するとともに, 新周波数帯の開拓に関する話題を紹介する.

Transmission Characteristics of Transponders

The Japanese Medium-scale Broadcasting Satellite for Experimental Purpose(BSE) was successfully positioned in a geostationary orbit on 26 April 1978. Various kinds of transmission characteristics were periodically measured every half year. Those were frequency responses and input-output characteristics of each electronics unit which made up a high power, 100W, transponder. No significant degradation of their characteristics was observed for about 2 years, and the characteristics of the in-orbit satellite transponders almost coincided with the designed values or the values measured at GE prior to launch. FM television signal(FM-TV) transmission characteristics were also measured periodically. From these measurements we concluded that the qualities of the television picture and sound were not reduced to any extent by the high power transponders.