To successfully carry out searching frequencies even in the case a referential clock with poor accuracy is supplied thereon.

In the case a value of the RSSI output from a transmitting/ receiving section of a PDC-P module is large, the frequency search at a high speed is realized by narrowing a range of the frequency to be searched in a GPS module. In the case the value of RSSI is small, failures in the frequency search are eliminated or reduced by widening the range of the frequency to be searched. Because the value of RSSI represents the intensity of a received signal and indirectly represents the accuracy of the referential clock REFCLK, the failures in the frequency search are eliminated or reduced by setting the range of the frequency to be searched in response to the value of RSSI, and therefore a required time for searching can be shortened as a whole.