| 摘要 |
PURPOSE:To prevent the deterioration of degree of separation, by controlling the gain and amplitude of FM and PM detection circuit at the output level of AM detection and avoiding the level difference between the sum signal obtained at the AM detection and the difference signal obtained at the FM and PM detection. CONSTITUTION:The output of the AM detection circuit 12 is inputted to the matrix circuit 16 and also to the rectifying circuit 19, where the DC voltage according to the level of the said detection output level is produced. The output of the rectifying circuit 19 is fed back to the high frequency amplifying circuit 10 and intermediate frequency amplifying circuit 11, and if the input signal level is increased, the gain control circuit keeping the output at almost constant value is formed. Further, the output of the rectifying circuit 19 is connected to the control terminal 48 of the amplitude limit circuit 13 to control the gain and amplitude of the amplitude limit circuit 13 in proportion to the antenna input level. Thus, the difference between the sum signal obtained at the AM detection circuit 12 and the difference signal obtained at the FM detection circuit 14 can be eliminated to prevent the deterioration of degree of separation. |
