| 摘要 |
PURPOSE:To eliminate the influence of external noises, temperature variation, etc., and to easily set a gain by comparing control contents which correspond to a detection output and characteristics of a detecting circuit with the storage contents stored in a ROM and calculating a control voltage. CONSTITUTION:A sample and hold circuit 10 holds a level with a clock for reception synchronization in synchronism with the clock. An adder 12 is an adder which adds the output of an A/D converter 11 and adds (i) samples (i: positive integer) and a subtracter 13 performs subtraction. This function is equivalent to the calculation of the mean value of the (i) samples and determines the time constant of an AGC loop. Then, the ROM 14 compares and output e0 with a detected voltage corresponding to the mean output. The ROM 14 is stored with respective values to be read out corresponding to inputs according to detection voltage characteristics of a detector 3. An adder 15 adds the ROM output to a constant voltage input VG and a 1dB (m)-bit digital attenuator 17 is controlled with the addition output.
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