| 摘要 |
PROBLEM TO BE SOLVED: To ensure stable reception by a receiving unit regardless of the meteorological conditions by using a drive circuit which generates a drive signal according the control signal that is supplied from a PLL circuit and a loop filter which changes the frequency characteristic of a loop according to the drive signal that is generated by the drive circuit. SOLUTION: A loop filter circuit part 140 connected to the loop filter connection terminals T2 and T3 of a demodulation IC 31 serving as a PLL demodulation circuit consists of a drive circuit 141 which generates a drive signal according to the switch signal that is outputted from the output port of a PLLIC and a filter circuit 142 which can change the frequency characteristic according to the drive signal that is generated by the circuit 141. When the switch signal which is supplied to the circuit 141 of the part 140 from the PLLIC is set at a high level, the pass band of frequency characteristic of the circuit 142 is reduced. Thus, the components other than a carrier are decreased and accordingly the noises can be decreased. |
