| 摘要 |
PURPOSE:To prevent the occurrence of distortion, by lowering the receiving sensitivity of the front end of super-regenerative system when the frequency of a quenching oscillating circuit included in said front end is increased. CONSTITUTION:When the amplitude of an input signal from an antenna 1 is large, the frequency of a quenching oscillating circuit 8 included in a front end 2 of the super-regenerative system at a connection point B is increased. The output from the connection point B is given to BPFs 21-23. BPFs 21-23 permit frequency components of frequencies f1-f2, f2-f3, and f3-f4, to pass through. Outputs of BPFs 21-23 have levels discriminated by level discriminating circuits 24-26 respectively; and if respective frequency components are higher than discrimination levels, outputs from circuits 24-26 are logical 1. For example, when the frequency of the connection point B is f3-f4, outputs of circuits 24 and 25 become logical 1, and relay switches 36 and 37 are excited to make relay switches 46 and 47 conductive. In accordance with this conduction, the base potential of a transistor 2 becomes higher to lower the receiving sensitivity. |
