Zero intermediate frequency receiver having an automatic gain control circuit

A zero intermediate frequency (zero IF) receiver, comprising:

• a first adjustable gain stage having an input terminal for receiving an input signal, the first adjustable gain stage being responsive to a gain control signal for adjusting the amount of gain provided to the input signal and providing an amplified output signal at an output terminal;
• first and second down mixers coupled to the output terminal of the first adjustable gain stage and providing first and second phase-related baseband signals;
• a second adjustable gain stage for receiving the first and second phase-related baseband signals and providing first and second amplified baseband signals in response to a modified gain control signal;
• a control means coupled to the first and second adjustable gain stages and responsive to the gain control signal for providing the modified gain control signal to the second adjustable gain stage for adjusting the gain of the second adjustable gain stage depending on the level of the modified gain control signal, the control means including a limiting means for limiting the maximum amount of gain reduction applied to the second adjustable gain stage upon the gain control signal reaching a predetermined gain reduction limit threshold level, wherein the gain of the first adjustable gain stage is reduced prior to the gain of the second adjustable gain stage;
• first and second up mixers for converting the first and second amplified baseband signals into first and second amplified phase-related signals;
• and
• an adder for summing the first and second amplified phase-related signals to produce the gain control signal.