| 摘要 |
PURPOSE:To prevent the lowering of receiving sensitivity which is caused by the noise, etc., by detecting the oscillation stop conditions of a quenching oscillating circuit included in a super-regenerative system front end and then controlling the quenching oscillating circuit based on the detection of the oscillation stop condition. CONSTITUTION:The input signal supplied through an antenna 1 is applied to a super-regenerative system front end 2 to be converted into a low frequency signal. This output is sent to a signal level discriminating circuit 5 via a low frequency amplifying circuit 3 and a band pass filter 4 to be converted into the DC voltage according to the amplitude. If the level of this DC voltage is higher than a prescribed value, a normal signal is decided to be delivered through a speaker 6 functioning as a display device. When some fault arises to the working of the front end 2, the frequency of a quenching oscillating circuit included in the front end 2 increases. Based on this oscillation stop conditions, the quenching oscillating circuit is controlled to obtain the optimum receiving sensitivity. |
