AUTOMATIC GAIN CONTROL CIRCUIT FOR DIGITAL MOBILE COMMUNICATION

摘要

PURPOSE:To reduce a maximum required time needed for the convergence of a transient characteristic only to the utmost while keeping a steady-state characteristic in the convergence characteristic of AGC(automatic gain control) the same as that of a conventional control circuit. CONSTITUTION:The control circuit is provided with a 3rd counter 3 that counts a prescribed value M smaller than a prescribed accumulated value N at which a 1st counter 1 counting an absolute value 1 of an output of an identification device 00 identifying the polarity of an error ERROR being a difference between an amplitude of reception output data and a reference amplitude is reset and that generates a signal R to reset the count M of the 1st counter 1 and with a bit operation section 4 deciding a setting value of a 2nd counter 2 one by one bit each depending on a count (-M-+M) till the 1st counter 1 is reset. Then the bit operation section 4 operated by an output of the 3rd counter 3 only for a prescribed transient period after the start of control operates each output bit of a setting value of the 2nd counter 2 depending on the count (-M-+M) of the 1st counter 1 to decide a step size of a control voltage Vc of a variable gain amplifier.