Integrated Design And Realization Of Limiting Low Noise Amplifier

Low noise amplifier is widely used in various radar and receiving systems.The noise coefficient of low noise amplifier directly determines the sensitivity index of receiving channel.In the case of amplifying the weak signal,the noise of the amplifier itself may interfere the signal seriously,so it is hoped to reduce the noise to improve the signal to noise ratio of the output.As the spatial electromagnetic signal becomes more and more complex at present,in order to improve the anti-interference ability of the receiving system and protect the receiving channel low-noise amplifier from being burned down,usually before the low-noise amplifier is added to protect the low-noise amplifier.In this thesis,the main application prospect and technical approach of limiter low-noise amplifier are analyzed from the basic theory of amplitude limiter and low-noise amplifier.In this paper,the balanced structure is adopted to realize the integrated design of amplitude limit and low noise.The characteristics of the balanced structure amplitude-limit and low noise amplifier are introduced.Detailed index decomposition of each part is carried out according to the principle block diagram.Secondly,the high-power bridge,high-power amplitude limiter and MMIC low-noise amplifier are analyzed and designed separately.Finally,the bridge,amplitude limiter and low-noise amplifier are jointly modeled and simulated for the integrated design of the whole index.This thesis,a small s-band limited-amplitude low noise amplifier with high reliability and high power tolerance is designed by using the hybrid integrated circuit of thin film technology.The high-power bridge,clipper circuit,and MMIC low-noise amplifier were optimized and integrated,which significantly reduced the volume of the whole product.The whole circuit adopts balanced structure,which improves the power capacity of the limiter and has high reliability.In this project,the sample of s-band limited-amplitude low-noise amplifier is produced according to the integrated design scheme of limited-amplitude low-noise amplifier.In the process of development,some problems of indicators or experimental aspects have occurred successively.After optimization and improvement,all the indicators of the final samples meet the requirements of the development target.The main indicators of limited-amplitude low noise amplifiers has a small signal gain is higher than 30 dB with a gain flatness below 0.4dB.Limited-amplitude low noise amplifiers has a noise figure below 1.3dB.Limited-amplitude low noise amplifiers provides input and output VSWR below 1.3,an output power at 1dB compression point of more than 10 dBm and an outline dimension of 11mm×26mm×6mm.Limited-amplitude low noise amplifiers can work in 300 W pulse power with a pulse width of 3 ms and a duty ratio of 30%.