Circuits, systems, and methods for managing automatic gain control in quadrature signal paths of a receiver

摘要

A system provides closed-loop gain control in a WCDMA mode and open loop control in an EDGE/GSM mode. Gain control is distributed across analog devices and a digital scaler in a wireless receiver. In the WCDMA mode, a loop filter generates an error signal that is forwarded to analog and digital control paths. The analog control path includes a first adder, a programmable hysteresis element, and a lookup table. The analog control signal is responsive to thresholds, which when used in conjunction with a previous gain value determine a new gain value. The digital control path includes a second adder, a programmable delay element, and a converter. A control word is responsive to a difference of the error signal, a calibration value, and the analog control signal. Blocker detection is provided in the WCDMA mode of operation. A controller sets system parameters using a state machine.

主权项

1. An automatic gain control (AGC) circuit comprising:
an analog control branch including a first feedback adder and a lookup table, the analog control branch responsive to a gain value from a baseband system and a first calibration value, the analog control branch configured to generate an analog control signal; a digital control branch including a programmable delay element and a second feedback adder, the programmable delay element configured to create a delayed analog control signal from the analog control signal, the second feedback adder configured to calculate a digital control signal based on the gain value from the baseband system, the delayed analog control signal, and a second calibration value; and a switching element configured to controllably provide the gain value from the baseband system to the analog control branch and the digital control branch.