| Project/Area Number |
02452151
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
電子通信系統工学
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| Research Institution | Takushoku University |
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Principal Investigator |
IKEGAMI Fumio Takushoku University, Faculty of Engineering, Professor, 工学部, 教授 (20093180)
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| Co-Investigator(Kenkyū-buntansha) |
KITANK Yasushi Takushoku University, Faculty of Engineering, Research Assosiate, 工学部, 助手
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥6,500,000 (Direct Cost: ¥6,500,000)
Fiscal Year 1991: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1990: ¥3,300,000 (Direct Cost: ¥3,300,000)
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| Keywords | Digital mobile radio / Multipath propagation / Multipath delay time / Mountain refrection / Theory / Measurement / 移動通信 / 周波数相関 / 建物回折損失 |
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| Research Abstract |
In digital mobile radio, delayed multipath waves cause serious degradation in error rates. Reflection by mountains can produce very long delay which influences the system performance. However, there has been no way of predicting the strength of mountain reflection. Our study aimes to clarify the fundamental characteristics of mountain-reflected signals and how to predict the strength of the signals reflected by a mountain.
Measurements of mountain-reflection have been made at 1.2GHz on the campus of Takushoku University, using directive antennas directed to a part of a mountain. The mountain-reflected signal was seperated by a sharp pulse inserted in a TV signal, and received pulse pattern was observed on CRT display and recorded and processed by a computer to give the receiver input signal level of the reflected signal component.
In parallel, theoretical analysis was made to calculate the reflected signal strength taking a reflecting mountain as an absorbing scattering plane. The absorption factor at a mountain surface can be calculated from the measured reflected signal strength. According to the measurement, the wave attenuation due to absorption is obtained to be about 26.5dB in this case. In the measurements, the reflected signal strength was observed to vary with time. For example, the reflection increased by several dB in a few hours after snowfall, and also rapid fluctuation was eventually observed.
As the results, a method of theoretical prediction of the mountain-reflected signal strength has been proposed for arbitrary propagation conditions, if the absorption attenuation of radio wave by the reflecting mountain surface is known. Further studies are necessary to prove the validity of the fundamental equation and the value of absorption factor for more generalized environments.
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