| 摘要 |
PURPOSE:To increase the time constant of an AGC loop by extracting an AGC signal, multiplying it with an input signal so as to obtain an output signal subjected to automatic gain control thereby preventing the reduction in a control force. CONSTITUTION:The digital AGC system is constituted by providing a timing generator 13 generating a set timing pulse being an integral number of multiple of the sampling period T and a switch 12 turning on/off a transmission circuit synchronously with the timing pulse. Through the constitution above, the sampling period T and the period S of the timing pulse are selected in the relation of S=4T, and an output M of a multiplier 7 in matching with the period T is inputted to the switch 12, where M is the output of the multiplier 7. The switch 12 receives the output N of the multiplier 7 in matching with the period T. Then the switch 12 is switched at a period S being four times of the period T and in outputting the timing pulse, the output M of the multiplier 7 appears at the output of the switch 12. Thus, the output M appears only when one period S exists in the four pulses having the period T as the output of the switch 12.
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