| 摘要 |
A radio relay apparatus including an outdoor relay unit formed of first and second receiving parts equipped out of doors and an indoor relay unit formed of third and fourth receiving parts, and a digital transmission line connecting the outdoor and indoor relay units enables radio communication even in a blind area such as an underground area and tunnel. In the first receiving part of the outdoor relay unit, a receiving antenna for receiving a high-frequency signal is integrally incorporated so as eliminate the transmission loss. The high-frequency analog signal is converted to its corresponding digital signal of a desired frequency band by a digital signal processor in the outdoor relay unit, and then, the digital signal thus obtained is transmitted to the indoor relay unit through the digital transmission line, so that high-quality radio communication can be accomplished.
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