Low Noise Amplifier Design And Achieve Based On GaAs HEMT

This paper mainly introduces the circuit design,circuit simulation,layout design,circuit test and debug of X band GaAs HEMT transistor low noise amplifier. It deeply researches the characters of low noise amplifier based on GaAs HEMT and optimization technique of CAD resign. Matching circuit, bias circuit and topology structure are all designed. It achieves low noise and high gain as small as possible.In this paper, it gives an introduction a lots of theories of low noise amplifier, including the description of two-port network, the classify of transmission line, Microstrip and noise theory and so on ; the circuit forms which are in common used are analyzed and balanced circuit is chosen in this design. The formulations of low-noise and high gain matching design are achieved according to the noise of two-port network and broadband matching theories. This LNA's working frequency is 8―12GHz.We use two-stage circuits of topology structure. This paper uses ADS design software. Each stage selects appropriate topology or circuit architecture appropriate for that particular LNA. Aim at noise factor, gain and VSWR proceed optimization. After each stage achieves design demand, cascade of two-stage circuit proceed optimization. The gain and noise are of great improvement. Then the DC bias circuit is given. The layout is simulated with Momentum simulator in ADS and the results are accord with the demand of the design. At last, the layout of the circuit is realized by Protel.At last, use the equipment in the lab, and analyze and test the circuit .Consider disperse heat, the jointing between parts of an apparatus and Miciostrip and ullage of this circuit. The separateness of transistor X band LNA achieves a gain of more than 10dB, and good gain flatness limit is 1dB in 8―12GHz band.