High-speed and low-complexity analog automatic gain control loop for UWB receiver

AGC(Auto-Gain-Control)is used in RF receivers to adjust gain of amplifier and achieve fixed output signal amplitude,thus signals with different energy can be received correctly.UWB (Ultra-Wideband) signals,whose bandwidth is extremely wide,give AGC design a new challenge.The paper presents a high-speed low-complexity circuit structure of analog AGC loop for UWB receiver.The AGC loop takes advantage of multi-stage variable gain amplifiers (VGA) for controllable and high gain,while using peak-detector and absolute-value-calculator to achieve the maximum absolute-value of complex signal.Comparing the maximum absolute-value to the reference voltage,the circuit creates a feed-back gain control voltage which can control gain of VGA to make power level of the output in accordance with the regulated input signal amplitude of ADC.Based on HJ 0.18μm CMOS technology,simulation results show that the proposed AGC loop can achieve a 40dB gain control while 3dB bandwidth is more than 500MHz,and IP3 is 20dBm,which proves that the AGC presented can meet the requirement of UWB receiver.