| 摘要 |
PROBLEM TO BE SOLVED: To provide an AGC circuit that attains a stable operations at a high-speed by eliminating the factors slowing down the response of an AGC loop caused by other factors than a coefficientεto decide a loop band. SOLUTION: The AGC circuit is provided with an AGC amplifier 1, a demodulator 2 that demodulates the output signal of the AGC amplifier 1, an analog/digital converter 3 that converts an output of the demodulator 2 into a digital signal, an envelope detection means 4 that detects an envelope of an output of the analog/digital converter 3, a sbutractor means 5 that calculates an error between a detection output of the envelope detection means 4 and a reference value, a 1st multiplier means 6 that multiplies a coefficient deciding a response speed with the calculated error, an integration means 9 that integrates an output of the 1st multiplier means 6, control voltage generating means 10, 12 that generate a gain control voltage of the AGC amplifier from an output of the integration means 9, and also provided with an output level discrimination means 14 that decides an output signal level of the 1st multiplier means 6, an output changeover means 15 that outputs a constant in response to the output level discrimination means 14, and a 2nd multiplier means 13 that multiplies further an output of the output changeover means 15 with an output of the 1st multiplier means 6.
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