| 摘要 |
PURPOSE:To detect signals always at constant SN in an auto-slice circuit detecting the existence or absence of a high frequency pulse modulated signal by forming slice voltage from an average DC component in a video noise detected by DC coupling. CONSTITUTION:A high frequency pulse modulated signal inputted to an input terminal 1 is detected by a negative polar envelope detector 2 and inverted and amplified by a video amplifier 3 while being DC-coupled and a positive polar video output 4 is inputted to a slice circuit 7 and an integral network 9. The integral network 9 consists of a low-pass filter and takes out a DC component in a video noise. The DC component is amplified by DC gain set up by a DC gain setting variable resistance 10 in a DC amplifier 11 to be used as slice voltage 5 of the slice circuit 7. If slice voltage VTH is set to 3Vn so that the slice circuit 7 detects a signal at SN=3 on the basis of a noise level Vn, the gain of the DC amplifier 11 is set up by the variable resistance 10 so that GD=3.Vn/VDG=3/k is satisfied. |
