| 摘要 |
PURPOSE:To reduce multipath noises by detecting AM components in intermediate frequency signals of two receiving circuits, comparing their detected levels with each other, and obtaining the output of one receiving circuit having a lower level. CONSTITUTION:Intermediate frequency signals from the intermediate frequency circuits 3 and 3' of two receiving circuits A and A' are AM-detected by AM detecting circuits 8 and 8' to extract only AM-modulated components. Those AM-modulated components are supplied to BPFs 9 and 9' to extract 19-60kHz components, which are rectified by rectifying circuits 10 and 10'; and their two rectification outputs are inputted to a comparing circuit 11 to compare their levels with each other. The circuit 11 controls a signal switching circuit 12 in such a way that a lower-level AM-modulated component from the detecting circuit 4 or 4' is led to an output circuit. The circuit 12 is controlled by utilizing an AM-modulated component generated during the generation of a multipath noise, so an AM-modulated component with less multipath noises is selected and outputted. |
