摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technology by which precision of a signal received from a satellite is estimated early. <P>SOLUTION: An antenna 10 receives a signal transmitted from at least one satellite. In a frequency discriminating part 28, a local signal of which the frequency changes over a range of Doppler shift to be generated in a received signal is generated, the received signal is subjected to frequency conversion by a local signal, envelope detection of the signal subjected to frequency conversion is performed, and the signal subjected to the envelope detection is compared with a threshold. As a result of the comparison, a CPU 20 counts the number of signal components equal to or more than the threshold, thereby estimating the number of satellites being transmission sources of the received signals. <P>COPYRIGHT: (C)2012,JPO&INPIT |