Design Of Automatic Gain Control Loop In Wifi Receiver

Since twenty-first Century,the wireless communication technology has made great progress.In the process of wireless signal transmission,its amplitude will be attenuated in different degrees,so that the dynamic range of the received signal will be larger.Automatic Gain Control is a loop system designed to stabilize the signal size.It plays an important role in the normal demodulation of the receiver.However,the WiFi signal has a higher peak to average ratio,and AGC needs to be completed within the time of 5.6us in short training sequence.Therefore,the stability and tuning speed of AGC have important influence on the performance of WiFi receiver.In this thesis,the structure and principle of AGC are analyzed,and a digital closed loop automatic gain control structure is adopted.In the power estimation section,an improved digital filter is adopted,which can estimate the power of the single baseband signal,avoid the estimation error caused by I and Q mismatch,and effectively improve the anti-interference ability.The PID algorithm is used in the gain adjustment.Compared with the previous single step gain adjustment method,it can achieve better balance between the regulation speed and the system stability through the optimization of parameters.At the same time,the system model of AGC is established in Simulink,and the feasibility of AGC scheme is verified by simulation.The final task is to complete the implementation of the AGC used hardware description language,build a hardware test platform,and make related tests.After testing,AGC in this thesis can control the gain of WiFi signals,The adjustment time of the AGC is less than 4.85us and the adjustment error is less than 100mV,which meets the design requirements and performance indicators,and has certain practical value in engineering.