| 摘要 |
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.
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