L-band Dual-frequency Boardband Low Noise Amplifier Design And Research

Low noise amplifier(LNA)is a key part in RF systems,which seriously impacts on the noise and linearity in the whole systems because of being placed in the first stage in receivers.Based on the design theory and methods,this paper presents a dual band LNA with novel Matching Network.According to the by requirement of subject,this thesis presents a dual-frequency boardband LNA operating at 1.2GHZ-1.25 GHZ and 1.556GHZ-1.608 GHZ,by reviewing the domestic and overseas development of researching LNA.The LNA is built by Avago's transistor ATF-54143 and the lumped elements provided by Murata.The bias circuit is designed by determining suitable quiescent point,which ensures the transistor operating in the state of absolute stability and prevents RF signals from entering the DC source.A parallel dual band structure is proposed to ensure LNA operating at two frequencies,at which the outputs are combined by a combiner with high isolation and highly matched ports.Based on stub line theory,a matching network with lumped elements and microstrips is designed,which has the both advantages of lumped and distributed elements matching networks.The LNA is designed by simulation software ADS and measured by Vector Network Analyzer.After optimization of two types of LNA,the return loss of the two ports are higher than 10 d B;the gain is approximately 30 d B;the gain flatness is lower 2 d B,and the simulated Noise Figure is lower than 1 d B.The design meets engineering requirement.This successfully designed LNA verified that the novel matching network is practical of designing a multi-stage LNA.A combiner with high isolation and highly matched ports can ensure the independent LNA work well in parallel dual band structure,which effectively enhances the circuit performance.