The Design And Implementation Of AGC Applied In RFID CHIP

Automatic Gain Control (AGC) automatically adjusts gain within coming signalof variable strengths and makes the output signal be constant or stability in a smallrange. So it is widely used in all kinds of communication systems and mixed signalcircuits, this paper is based on National Science and Technology Major Projects“development of bandwidth and frequency variable wireless broadband RF chip forindustry professionals network”, it mainly research the integratedAGC amplifier.This paper introduced the application of AGC amplifier’s background andcurrent research situation in china and abroad, from the basis of the overall structureand start amplifier design. This paper analyzes the basic principle of AGC amplifier,completed a high-performance AGC amplifier based on wireless RF chip.The proposed AGC circuit uses the closed-loop feedback technique to get thedesigned output voltage amplitude. AGC loop circuit mainly consists of a two-stageVariable Gain Amplifier (VGA) chain with DC offset canceller (DCOC), a peakvoltage detector, an error amplifier, a loop filter, and an exponential gain controlcircuit. VGA is the key part of AGC system, and it can adjust gain according tofeedback control signal. To get enough gain range, the presented AGC circuit employstwo-stage VGA chain. Peak voltage detector is used to detect the peak values ofVGA’s output. To keep VGA with a linear in dB characteristic, the exponential gaincontrol circuit is utilized to supply exponential control signal for VGA.The AGC circuit is based on cadence system and implemented in a standard GF0.18μm CMOS process. The simulation results confirm that this circuit operates witha supply voltage of3.3V, consuming26.4mW at room temperature (27°C), and thegain range is60dB(-15dB~45dB), It’s signal bandwidth is2MHz for differentialoutput400mVpp.