此論文設計一個適用於凱氏衛星天線的低雜訊放大器(LNA)，工作區域為X頻段7GHz ~ 9GHz，其中採用Agilant公司的ADS(Advanced Design System)軟體進行模擬。主要模擬的重點在於LNA放大電路優化及輸入輸出阻抗匹配、雜訊指數、功率增益等，藉由調整其中電路元件參數，來設計出系統最佳效能。由模擬結果顯示此LNA在全頻段具有至少13dB功率增益、雜訊指數小於3dB，輸出返回損失小於-17dB的低雜訊放大器。 A low noise amplifier(LNA) suitable for Cassegrain antenna applications is designed in this thesis. Which works in X band 7GHz ~ 9GHz. Here we adopt as Advanced Design System(ADS) published by Agilant corp. for simulation. The Main simulation points are LNA circuit optimization, input/output impedance matching, noise figure, power gain. Through adjusting the component parameter of the LNA circuit, the system optimization can be determined. Simulation results show that the LNA at X band is characterized by at least 13dB of power gain, less than 3dB of noise figure, and output return lose less than -17dB.
