| 摘要 |
PURPOSE:To improve the diversity effect by changing a switching threshold in accordance with the variance of a reception electric field. CONSTITUTION:A signal 101 of the antenna selected by an antenna switching circuit 1 is not only inputted to a power detecting circuit 2 but also outputted to a receiving part from a terminal 10. When the power of the reception signal is obtained by the power detecting circuit 2, it is compared with the switching threshold stored in a memory 5 by a comparator 3 as the first comparator, and the comparator 3 outputs a switching signal 103 to the antenna switching circuit 1 if the reception signal power is smaller than the switching threshold. Simultaneously, a power detection circuit output 102 is written in the memory 5 as the switching threshold. If the reception signal power is reduced gradually by this operation, the switching threshold is made smaller gradually. If the reception signal power is increased contrarily, the switching signal 103 is not generated because the output 102 of the power detecting circuit 2 is always larger than the switching threshold in the memory 5. A comparator 4 as the second comparator outputs a memory update signal 104 when the difference between the reception signal level and the switching threshold exceeds a certain value. |
