SIGNAL PROCESSING CIRCUIT

PURPOSE:To provide a signal processing circuit for a digital automatic gain controller able to decrease a carrier-off detection time. CONSTITUTION:The processing circuit is made up of an analyzer 101, a setting circuit 102 setting a cycle number required for level extraction for the analyzer 101, a discrimination device 103 discriminating the analyzed value, an adder 104 adding a level (e) for a fine gain variable to a controlled value to use the result for a control variable, a subtractor 105 subtracting the level (e) from the control variable to provide the result as a control variable, a discrimination device 106 discriminating the control variable with a control variable (y) equivalent to a carrier-off level, an output device 107 outputting the result of discrimination of the control variable, a comparator 108 and an adder 109 adding a value being a multiple of (m) of the gain variable level to a variable gain control variable and the carrier-off is detected without taking much time even at the carrier-off from an input of a large signal.