Design And Implementation Of High Performance AGC Control Scheme In Software Defined Radio Platform

With the development of wireless communication,Software Defined Radio(SDR)has attracted more and more people's attention.The core idea of SDR is to implement wireless communication functions by software as much as possibly and a variety of protocol standards can be implemented through software,so that it can be used in various communication platform where the standards coexist.Due to its flexibility,scalability and reliability,SDR technology has been widely used in many commercial,civil and military products.However,the wireless radio signal is subject to varying degrees of attenuation during transmission because of the complex environments,and the dynamic range will become very large,which has an important impact on receiving equipment,and may even results in the inability to demodulate signals.Therefore,Automatic Gain Control(AGC)is required in the SDR platform to adjust signal in real time and improves the dynamic range of the receiving device.This thesis designs and implements digital AGC based on project indicator requirements.Firstly,the basic knowledge of AGC is introduced,and the digital AGC is divided into three modules according to design indicators: external AGC,internal AGC and squelch.The external AGC mainly ensures that the signal is in the dynamic range of the ADC after passing through the RF amplifier.The internal AGC adjusts the in-band signal level to the target range to improve the processing ability of the small signal in the latter stage.The squelch is to prevent the internal AGC from amplifying noise mistakenly.In order to eliminate the influence of stabilization time between the external AGC and the internal AGC,a gain compensator is inserted between them.Then the three modules of external AGC,internal AGC and squelch are analyzed and designed in this thesis.the external AGC adopts a numerical control closed-loop structure,and this thesis performs matlab simulation analysis on the designed algorithm.In order to save hardware resources and meet the requirements of stable time,the internal AGC adopts exponential full digital structure and it is analyzed the stability through simulation and gived the estimation formula of stability time through matlab.At the same time,an automatic squelch algorithm is designed in this thesis,the simulation results show that the algorithm can effectively prevent the internal AGC from amplifying the noise.Finally,the digital AGC is implemented by Xilinx System on Chip(SoC)ZYNQ XC7Z020 which used as the hardware platform.The modules test and system comprehensive test are completed in this thesis.The test results show that the digital AGC in this thesis can work effectively and the dynamic range can reach 125 dB,the maximum error is 0.7dB,and the stable time is adjustable in three gears,which can meet the design requirements and performance indicators.