Research On Radio Frequency Front End Automatic Gain Control Circuit Of Wireless Receiver

Automatic Gain Control(AGC)is an important method to enlarge the dynamic range of RF receiver.It can ensure that the output power is stable in a small range when the input power varies greatly.AGC circuit is widely used in a variety of wireless receivers,hard disk reading,radar and medical equipment.This paper aims to study an AGC circuit for the RF front-end of wireless receiver,the main work of this paper can be summarized as follows:(1)A two-stage low noise amplifier(LNA)and MMIC amplifier has been designed.The two-stage LNA adopts ATF54143 transistor and joins high-pass matching network into inter-stage matching.In the 2.3GHz?2.6GHz frequency band,the measured gain is greater than 32dB,the gain flatness is less than 0.5dB and the noise figure is less than 1.5dB;The MMIC amplifier adopts the SGA6589 integrated chip to achieve a gain of 16dB and the return loss of both ports is greater than 12dB.(2)An electrically adjustable attenuator and a serrated directional coupler have been designed.Electrically adjustable attenuator adopts the PIN diode of SMP1307-011 model,which realizes the attenuation value range of 5?37dB when the tuning voltage is 1?16V.The isolated port of the serrated directional coupler is connected to a 50? resistor as load.The sector microstrip connection is used to achieve RF grounding.This structure ensures performance and is easy to machine.The measured coupling degree is 16dB and the isolation is greater than 30dB.(3)A power detector and a control circuit have been designed.The power detector adopts AD8362 chip to achieve a power detection range of-52?-+8dBm.The control circuit is composed of a single chip microcomputer MSP430 and a booster circuit.The MSP430 processes the output voltage from the detector,and output a varying voltage,and then control the electrically adjustable attenuator through the boosting circuit to achieve automatic gain control.In this paper,ADS2009 is used to complete the simulation of two-stage LNA,electrically adjustable attenuator and MMIC amplifier.HFSS15 is used to complete the simulation of coupler.Multisim14 is used to complete the simulation of power management module.Altium Designer 09 is used to complete the PCB design.At 2.45GHz,the test results show that the AGC circuit can realize the dynamic range of 31dB and the bandwidth of 300MHz.