| 摘要 |
<p>PURPOSE:To stop the search of a satellite signal only when the cause of reception interruption is an obstacle by providing a noise detection part, which detects the level of noise outputted by an antenna, and a decision part to stop a control part when the level of the noise detected by this noise detection part is higher than the noise level in a state that the arrival of radio waves from a transmission source to the antenna is not interrupted. CONSTITUTION:A level detection circuit 13 converts the noise to a direct current level. The output signal of the level detection circuit 13 is branched to the signal, which is inputted through a hold part 14 to a comparator circuit 15, and the signal to be directly inputted to the comparator circuit 15, and the output of the comparator circuit 15 is inputted to a microcomputer 16. The comparator circuit 15 decides whether the noise level detected by the level detection circuit 13 is higher than the noise level temporarily held by the hold part 14 or not, and outputs a decided result to the microcomputer 16 in a decision part 5. The level detection circuit 13, hold part 14 and comparator circuit 15 are controlled according to the program of the microcomputer 16.</p> |
