| 摘要 |
PURPOSE:To reduce noise due to multi-path disturbance by detecting the multi- path disturbance by another control circuit at a time other than the processing time of a control circuit, and switching a receiving antenna, allowing to prolong the observing period and to eliminate the deterioration in the S/N of the clock frequency. CONSTITUTION:A control circuit 30 provided separately consists of a detecting circuit 31 detecting the multi-path disturbance, driving signal generating circuit 32 forming an input of the driving circuit of an antenna switching circuit 3, and a processing time deciding circuit 33 deciding a processing time width T1. An output of the circuit 32 generates a positive pulse by setting an output of the circuit 33 to zero level in the processing time T1 and to 1 level at a time other than the processing time, every detection of the multi-path disturbance only at a time other than the processing time. This signal becomes one input to a signal coupling circuit 34, and since the input from a signal coupling circuit 13 is at zero level in this case, the output of a 1st driving circuit 14 is inverted at a time other than the processing time by a trigger signal by the output of the circuit 32. Thus, the switching of the receiving antenna is attained to the detection of multi-path disturbance in and outside of the processing time in such a way. |
