| 摘要 |
PROBLEM TO BE SOLVED: To properly maintain a digital broadcast reception status in a closed (radio ave shielding) space, such as, in an underground shopping area, without leaking radio waves to the ground during relaying of digital broadcasting. SOLUTION: A radio relay system 10 is equipped with a transmitter 12 and a receiver 14. A reception state input portion 25 of the transmitter 12 obtains the reception state grasped by the receiver 14 as a reception state informing signal 36. A transmission power control portion 23 outputs a transmission power control signal 34, according to the reception state of the receiver 14 to control the signal amplification portion 21 so that optimum output is obtained. The transmission antenna directivity change portion 24 outputs a directivity change signal 35, according to the reception state of the receiver 14 to adjust the directional characteristics of radio waves output from the transmission antenna portion 22. COPYRIGHT: (C)2009,JPO&INPIT |
