A gain control system in a Direct Conversion Receiver or similar receiver,
includes an automatic gain control circuit which determines whether a low
noise amplifier, which amplifies signals from an antenna prior to mixing
with signals from a local oscillator, should be set to a high gain or a
low gain. The output of the mixer is analyzed by a blocker detect circuit
to determine whether a blocker signal is present. Based on the presence
of a blocker signal and the power level of the useful signal, the gain of
the low noise amplifier may be reduced from the high gain to an
intermediate gain in order to reduce self mixing between the radio
frequency and local oscillator ports of the mixer, which may lead to
dynamic DC offsets.