Mathematics – Logic
Scientific paper
Jan 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002iaf..confe.608m&link_type=abstract
IAF abstracts, 34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA.,
Mathematics
Logic
Scientific paper
1. INTRODUCTION Rain attenuation in the 21-GHz band is much larger than that in the conventionally used 12-GHz band and the rain attenuation causes more serious program interruptions compared with that in the 12-GHz band. We are now studying an advanced broadcasting satellite in the 21-GHz band that enables adaptive compensation for heavy rain area by boosted beams using an on-board phased-array-transmitting antenna. To know the scale of this satellite system, it is important to estimate transmitting power needed to compensate for rain attenuation. Rain attenuation has so close association with rainfall that it is possible to estimate rain attenuation by measured rainfall. Japan meteorological agency is measuring 1-hour rainfalls for about 1300 locations in Japan. In this study, 1-hour rainfall data accumulated at more than 1000 locations over a period of 20 years were used statistically to grasp rainfall distribution throughout Japan and the transmitting power for compensation was estimated by use of these data. 2. CALCULATION MODEL FOR TRANSMITTING POWER ESTIMATION Assumed rain attenuation compensation area for Japanese archipelago was divided into 112 square areas. A size of each square was 0.1 degree in terms of azimuth and elevation angle for the beam direction of satellite transmitting antenna. For calculation, the link margin of 3.5 dB for clear sky was given to the area where 1-hour rainfall not larger than 3 mm was detected. For other square areas where 1-hour rainfall larger than 3 mm was detected, the link margin of 12 dB was given. The former link margin corresponds to the service availability of 99 % and the latter does to that of 99.9 % in an average year in Tokyo. A total system efficiency included radiation efficiency of the transmitting antenna of 1.0 was assumed. As modulation scheme, trellis coded 8-PSK (TC8PSK) was assumed. The required reception CN ratio for TC8PSK is 10.7 dB. As to TC8PSK, the baud rate of 57.72 Mbaud gives more than 100 Mbps of information bit rate with using TC8PSK. For direct home reception, the reception antenna of 45 cm diameter was assumed. 3. RESULTS The average frequency of compensation with respect to each required transmitting power was obtained. It was shown that there was no case of simultaneous compensation necessary for all 112 square areas due to rain attenuation in 20 years. The frequency of simultaneous compensation for 45 square areas was once in an average year and the transmitting power per one channel needed to compensate for the 45 areas was about 470 W. This power of 470 W corresponds to about 60 % of transmitting power to compensate for all 112 square areas. This is because heavy rain tends to occur locally and it is expected that the on-board phased-array-transmitting antenna is effective for the compensation. 4. CONCLUSION Transmitting power estimation for a broadcasting satellite in the 21-GHz band was studied focusing on compensating for rain attenuation in this paper. As a result, it has been found that the transmitting power of about 470 W/ch. was enough to achieve stable satellite broadcasting in the 21-GHz in Japan.
Kawaguchi Yutaka
Minematsu Fumiaki
Nakagawa Hitoshi
Tanaka Shoji
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