Circuits, systems, and methods for managing automatic gain control in quadrature signal paths of a receiver
First Claim
1. A method for managing automatic gain control in quadrature signal paths of a radio-frequency subsystem of a wireless communication system, the method comprising:
- determining a first signal strength at an input to a channel select filter in a digital receiver path and a second signal strength at an output of the channel select filter;
comparing the first and second signal strengths to detect whether a blocker is present in the quadrature signal paths of a receiver of the radio-frequency subsystem;
in response to detecting the blocker, forwarding a blocker presence signal to an analog control branch of an automatic gain control circuit, the automatic gain control circuit including a loop filter coupled to the analog control branch and a digital control branch, the digital control branch generating a digital control word configured to adjust a scaler coupled to the channel select filter; and
in response to not detecting the blocker, determining a difference between the second signal strength at the output of the channel select filter and a reference signal power, and applying the difference between the second signal strength and the reference signal power to the automatic gain control circuit.
1 Assignment
0 Petitions
Accused Products
Abstract
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.
-
Citations
29 Claims
-
1. A method for managing automatic gain control in quadrature signal paths of a radio-frequency subsystem of a wireless communication system, the method comprising:
-
determining a first signal strength at an input to a channel select filter in a digital receiver path and a second signal strength at an output of the channel select filter; comparing the first and second signal strengths to detect whether a blocker is present in the quadrature signal paths of a receiver of the radio-frequency subsystem; in response to detecting the blocker, forwarding a blocker presence signal to an analog control branch of an automatic gain control circuit, the automatic gain control circuit including a loop filter coupled to the analog control branch and a digital control branch, the digital control branch generating a digital control word configured to adjust a scaler coupled to the channel select filter; and in response to not detecting the blocker, determining a difference between the second signal strength at the output of the channel select filter and a reference signal power, and applying the difference between the second signal strength and the reference signal power to the automatic gain control circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. A system for automatic gain control in a radio-frequency subsystem of a wireless communication system, the system for automatic gain control comprising:
-
a power estimator configured to receive a first input from a digital receiver path and a second input from a channel select filter and to generate a first estimate of the signal power present at an output of the digital receiver path and a second estimate of the signal power present at the output of the channel select filter; a blocker identification element arranged to receive the first estimate and the second estimate from the power estimator and configured to generate a blocker presence signal when a function of the first estimate and the second estimate exceeds a threshold value; a converter coupled to an output of the power estimator and configured to generate a logarithmic representation of the first estimate of the signal power at the output of the digital receiver path; and an automatic gain control circuit arranged to receive the blocker presence signal and a difference of a reference signal and the logarithmic representation of the first estimate of the signal power at the output of the digital receiver path, the automatic gain control circuit including an analog control branch configured to generate a control signal and to generate a phase compensation signal when the control signal directs a change in a gain of a low noise amplifier. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
-
-
24. A circuit for automatic gain control in a radio-frequency subsystem of a wireless communication system, the circuit comprising:
-
a receiver including an analog receiver path coupled to a digital receiver path; and a radio-frequency automatic gain control circuit including an analog control branch having a first feedback adder and a lookup table, the analog control branch configured to generate an analog control signal to adjust at least one controllable gain element in the analog receiver path, and a digital control branch having a second feedback adder, a programmable delay element, and a converter element, the digital control branch configured to generate a control word responsive to a gain value received from a baseband element, a second calibration value, and a delayed representation of the analog control signal. - View Dependent Claims (25, 26, 27, 28, 29)
-
Specification