Patent ID: 7149263

Claim:
An Automatic Gain Control (AGC) method for a digital radio receiver, wherein a gain of an amplifier of said receiver is automatically changed in accordance with a level of a signal received by the digital radio receiver thereby to control a gain, the method comprising the steps of: (a) detecting instantaneous values of envelope of the input received signal sequentially at predetermined time intervals; (b) determining a first interval average value providing an average of instantaneous values for a first predetermined time length before an instantaneous value detected, and determining a second interval average value providing an average of the instantaneous values during a second predetermined time length shorter than the first predetermined time length before the instantaneous value detected; (c) determining a difference between the instantaneous value and the first interval average value; (d) in the case where the difference exceeds a predetermined threshold value, setting the gain of the amplifier at a value corresponding to the second interval average value during the second predetermined time length before the instantaneous value upon the lapse of a third predetermined time length from the time when the difference exceeds the predetermined threshold value; and (e) maintaining, during a fourth predetermined time length following the lapse of the third predetermined time length, the gain to the value set in step (d), and at each detection time point of the instantaneous value after the lapse of the fourth predetermined time length, setting the gain to a value corresponding to the first interval average value during the first predetermined time length before the instantaneous value.