Automatic gain control system and method for a ZIF architecture

A ZIF radio for detecting an RF signal within a predetermined power spectrum relative to a predetermined minimum noise floor, comprising:

• a ZIF receiver front end that converts the RF signal to a baseband signal and that includes a baseband amplifier;
• an overload detector, coupled to said ZIF receiver front end, that detects an overload condition of said ZIF receiver front end in which said RF signal is within an upper power range of a predetermined power spectrum and that asserts an overload signal indicative thereof;
• an analog to digital converter (ADC), coupled to said ZIF receiver front end, that converts said baseband signal to a digital baseband signal;
• a saturation detector, coupled to said ADC, that detects a saturation condition of said ADC in which said RF signal is within a middle power range of the power spectrum and that provides a saturation signal indicative thereof;
• a DC and power estimator, coupled to said ADC, that estimates DC and power level of said digital baseband signal and that provides estimation signals indicative thereof;
• and
• control logic, coupled to said saturation detector, said overload detector and said DC and power estimator and operatively coupled to said ZIF receiver front end via AGC and DC loops, that limits gain of said baseband amplifier to a maximum gain setting sufficient for said ADC to view a lower power story including the minimum noise floor of the power spectrum, that monitors said saturation, overload and estimation signals, and that switches gain of said baseband amplifier once to place the received signal within view of said ADC in the event of either one of said overload and saturation conditions.

A processing system with wireless communications, comprising:

• a processor;
• a memory coupled to said processor;
• and
• a ZIF transceiver, communicatively coupled to said processor, that detects RF signals within a predetermined full power spectrum, comprising:
• a ZIF receiver front end including a low noise amplifier (LNA), a DC subtractor and a baseband amplifier;
• an analog to digital converter (ADC), coupled to said ZIF receiver front end, that converts said baseband signal to a digital baseband signal;
• a saturation detector, coupled to said ADC, that detects a saturation condition of said ADC indicative of a medium-powered signal;
• an overload detector, coupled to said ZIF receiver front end, that detects an overload condition of the baseband signal indicative of a strong signal;
• a joint DC and power estimator, coupled to said ADC, that estimates DC and power level of said digital baseband signal;
• and
• AGC/DC control logic, coupled to said ZIF receiver front end, said overload detector, and said joint DC and power estimator, that employs full utilization of visibility of said ADC to limit gain of said baseband amplifier to a maximum gain setting and to segment said full power spectrum based on said overload and saturation conditions, and that employs limited gain stepping to avoid exceeding a DC budget of said ADC when switching gain of said baseband amplifier.