AUTOMATIC GAIN CONTROL DEVICE

摘要

A reception signal level is detected for each of the broad band, intermediate band, and narrow band and converted into a digital signal. According to the signal level of each band, a DSP (18) determines the enabled/disabled state of the gain adjustment of an LNA (3) and an attenuator (4) as well as a gain adjustment amount. For example, even when the signal level in the broad band and the intermediate band is greater than a predetermined value, the gain adjustment is not performed if the signal level of the narrow band including the reception-desired frequency does not exceed a predetermined value. Moreover, when the signal level in the narrow band is greater than the predetermined value and the attenuator (4) exceeds a limit level where gain can be adjusted, the gain adjustment amount by the attenuator (4) is maintained in the vicinity of the limit level while the gain of the LNA (3) is adjusted so that the gain is greatly lowered as a whole.