| The realization for seamlessly global communication becomes difficult for the fact of multi-standard, multi-frequency band and multi-mode in communication systems. Then, Software Radio architecture has been developed to meet higher requirement for both military application and civil application. Based on all-purpose hardware platform and flexible switching and upgrade software, Software Radio will turn true the fluently global communication, such as compatibility between systems of different standards and modes. For the purpose of multi-band, broadband Low Noise Amplifier (LNA) is needed on Software Radio.In this paper, major indexes for LNA are introduced firstly. After equaling LNA to 2-port microwave network, steps for LNA design are presented. Then, LNA works with good power gain and noise figure, but bad input VSWR (Voltage Standing Wave Ratio), output VSWR and gain ripple. Bad aspects then degrade bandwidth of LNA. To avoid this, balanced amplification technology is applied to the design of the LNA. The method is proved feasible by results. The LNA reaches absolutely stable, 10dB power gain, less than 1. 182dB noise figure, less than 0. 6dB gain ripple and less than 1.3dB input and output VWSR from 5. 3GHz to 6. 3GHz. |
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