| CPC H04W 52/52 (2013.01) [H03F 3/24 (2013.01); H03G 3/3042 (2013.01)] | 15 Claims |

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1. A power detector for an automatic gain control system, wherein the power detector is configured to detect an output power of a trans-impedance amplifier and adjust, by a control logic unit, a gain or an output power of a low noise amplifier connected to a radio frequency signal, the power detector comprises:
a detection circuit, which has a first input terminal connected to a first differential output terminal of the trans-impedance amplifier and a second input terminal connected to a second differential output terminal of the trans-impedance amplifier, and is configured to sample a peak of a differential output signal of the trans-impedance amplifier along with a clock cycle and provide a differential detection signal at a first output node; and
a filter circuit, which is connected to the detector circuit, and is configured to convert energy of the differential detection signal obtained at the first output node into an output voltage.
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