| 摘要 |
An automatic gain control (AGC) system controls a receiver having multiple amplifier stages with near constant compression. The AGC system controls gain, and thus compression, of each stage employing information generated by the other stages to generate feedback signals at a system level. A central controller uses threshold detection to monitor signal power at each stage of the receiver signal path as well as overall signal gain. Based on these various signal power measurements, the central controller adjusts signal gain of the input to one or more stages, while maintaining overall signal gain for a constant output signal level. The AGC function may be implemented by switching the gain of each stage's variable amplifier in discrete steps in discrete steps, with the step size being coarser for stages closer to the input signal than those closer to the final output baseband signal. Monitoring power of the signal at these points as the signal passes through the series chain of components may also allow for resolution of the desired signal from unwanted interferer signals coincident with the desired signal. Resolution of the desired signal at each stage may further allow for refinement of the gain settings within the receiver. System level feedback may enhance stability and provides the following flexibilities. First, attenuation of the signal as it passes through, for example, the RF/IF receiver is done in discrete steps. Second, the circuit may be relatively easy to implement in integrated circuit (IC) technology. Third, the present invention allows for constant compression, in turn allowing processing of relatively high-level, input signals.
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