| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide the automatic gain control(AGC) circuit which is operated stably without being affected by an interference wave by dividing all bands of a spread spectrum reception signal into a plurality of bands, eliminating an output for a narrow band including the interference wave, calculating the electric field strength and controlling the attenuation. SOLUTION: Four filters of a filter section 2 each covering 1/4 of the entire frequency bands are used to split the frequency band of a reception signal from an input terminal 101, a switch section 3 selects sequentially each output signal, the selected signal is given to a detection section 5, in which an average amplitude is detected. The output signal from the detection section 5, that is, the signal denoting the electric field strength of the signal via each filter is given to a control value generating circuit 6, in which the signal is sequentially stored. The electric field strength of the signal from the filter in which an interference wave is mixed is eliminated, the mean value of the electric field strength signals of the remaining filters is calculated as the electric field strength for the entire band. The attenuation of a variable attenuator 1 is controlled by a control signal 103 denoting the result of calculation for the AGC operation.</p> |
