US 6,285,863 B1 · System and method for providing automatic gain control with high dynamic range

Abstract

A system and method for providing automatic gain control (AGC) with high dynamic range. An AGC system comprises an open loop control system and a closed loop control system. The open control loop system senses the power level of an input signal and preprocesses the input signal based on its sensed power level. For instance, a strong input signal is attenuated by a fixed level via an analog attenuator, a weak input signal is amplified by a fixed factor via a low noise amplifier, and an intermediate level input signal is directly passed to the closed loop control system of the AGC without any attenuation or amplification. By preprocessing the input signal, the closed loop control system can operate in a range that is optimal for its performance. For instance, a gain variable amplifier of the closed loop control circuit can be prevented from operating in a high attenuation status where its noise figure is very high. A wide band receiver using the AGC system may have a dynamic range over 100 dB.

Claims22

Dependent claims

An automatic gain control (AGC) system, comprising:

an open loop control system for sensing a power level of an input signal to the AGC system and preprocessing the input signal based on its sensed power level;
and
a closed loop control system comprising a gain variable amplifier (GVA) for variably amplifying the preprocessed input signal to maintain an output signal of the AGC at a predetermined power level, wherein the preprocessing of the input signal places the input signal within a power level range that maintains an optimized operation range for the GVA and maintains a signal-to-noise (S/N) ratio of the AGC system above a predetermined S/N level.

A radio frequency (RF) receiver, comprising:

a downconverter for converting an RF input signal into a intermediate frequency (IF) signal;
a first power splitter for dividing the IF signal into an IF input signal and a first IF sample signal;
and
an automatic gain control (AGC) circuit comprising
an open loop control circuit for sensing a power level of first IF sample signal and preprocessing the IF input signal based on the sensed power level of the first IF sample signal;
and
a closed loop control system for variably amplifying the preprocessed IF input signal to maintain an output signal of the AGC at a predetermined power level, wherein the preprocessing of the IF input signal places the power level of the IF input signal within a range that maintains a signal-to-noise (S/N) ratio of the receiver system above a predetermined S/N level.

4 more elements

Dependencies are inferred from the claim text.

System and method for providing automatic gain control with high dynamic range

Life of this patent

System and method for providing automatic gain control with high dynamic range

Life of this patent

Abstract

Claims22