Design Of Ultra-small Signal Low Noise Amplifier

As a new technology,wireless communication network system has replaced a lot of manual work in the application,which greatly improves the work efficiency,and realizes the intelligence,as one of the most important part in the wireless communication system,the low noise amplifier of the RF front-end is mainly used to amplify the small signal,and to provide it to the subsequent stage.Over the years,so many domestic and foreign scholars have done extensive and in-depth research on transistors of LNAs,and constantly improve the performance of devices,manufacturing processes,etc.Constantly optimize the operating frequency,bandwidth,gain,noise,linearity,power consumption of LNAs,to find the best match to achieve the compromise of each parameter.In this paper,firstly,the basic definition and concept of noise figure are expounded,including the expression formula of the noise figure,influence factors of noise figure,characterization of noise figure,the power spectral density of noise figure,and the noise figure of cascaded network.The noise figure is explained from two aspects:physical characteristics and semiconductor technology,summarizes the solution of the different types of noise amplifier,according to the semiconductor components of various categories of the small signal model and the noise equivalent circuit,analyzed principle and deduced formula of the equivalent input noise voltage and equivalent input noise current of BJT,FET,two port components.Secondly,this paper introduces the analysis method and the technical index of LNAs,the impedance parameters and scattering parameters of the two port network,and the basic sense of these parameters.Then introduced the main technical index of LNAs,such as working frequency,power gain,gain flatness,VSWR,P1dB,dynamic range and 3rd order input intercept point.Then the stability of the amplifier is analyzed in detail,and provided several methods of stability of the amplifier circuit.Finally,the low noise RF transistor ATF-54143 of Avago company is used,with RF circuit simulation software ADS of Keysight company,analyzed and designed DC signal,stability,input and output impedance matching,at the same time,considering the noise figure,gain,stability and VSWR of the amplifier,the whole circuit is optimized.The simulation results show that the gain of LNA reaches 10dB and the noise figure is less than 1,which meets the requirements of the subject,and the PCB layout of the low noise amplifier is designed by using Altium Designer software.