| 摘要 |
PURPOSE:To enable to hold sufficiently high for an AGC loop gain, by constituting an RFAGC circuit operated with the output of an IFAGC circuit with an error amplifier picking up the difference between the peak value and the threshold value, peak value detection circuit and LPF. CONSTITUTION:An output signal (a) from a peak value detector 9 of an IFAGC circuit 62 is applied to an error amplifier 11' of an RFAGC circuit 72, a pulse output corresponding to the difference with a fixed threshold value (b) is picked up from the amplifier 11' and applied to a peak value detector 15. A signal (f) in proportion to the peak value of the output pulse of the amplifier 11' is picked up from the detector 15, and the signal (f) is averaged at an LPF13 and picked up as an RFAGC voltage (g). Since the detector 15 detects the peak value of the output pulse of the amplifier 11', it is not subjected to the variation of the pulse width of the amplifier 11' and since the voltage (g) is the average of the peak value detected output, sufficiently greater level can be picked up and the loop gain of the RFAGC can be kept sufficiently higher. |
