| 摘要 |
PURPOSE:To improve the resolution of a received picture by generating a signal for a decrease in reset level from a PAM signal, by generating a signal varying in threshold level from said signal, and by comparing this threshold-level signal with the PAM signal. CONSTITUTION:A PAM picture signal 9 inputted from a terminal 2 is inputted to the terminal t1 of a comparator 5 and also supplied to a reset-level component eliminating circuit 3. The circuit 3 consists of resistances, a capacitor, and an integration circuit of an operational amplifier 9, and a signal obtained by integrating a signal (a) and removing a reset-level component is inputted to a threshold-level generating circuit 4. The circuit 4 consists of diodes 13 and 14 in parallel and in the opposite directions, a capacitor C15 charged and discharged by the signal (c), and voltage limiting circuits 16 -20 which limit the voltage variation of the C15 to constant range to determine the upper-limit value and lower-limit value of the voltage variation, and generates and input a threshold-level signal (d), which varies following up the signal (c), to the terminal t2 of the comparator 5. The comparator 5 compares the signal (a) with the signal (d) to discriminate a signal, which has much less amplitude variation, on binary basis with fidelity, thereby outputting a signal (e). |
