Research And Design S Band Low Noise Amplifier

Low noise amplifier is widely used in PCS base stations, GPS and WLAN. LNA is a key block of the front end of receiver to amplify RF signal, and its performance will directly influence the whole system. With the development of science and technology, the requirement for the performance of LNA becomes much higher. The currently research focus about LNA is how to make it more compact, lower noise, higher gain, wider dynamic range, more stable and reliable.Firstly, the basic theory of LNA and the relevant knowledge of microwave circuits were elaborated on this paper. And then the working principle and advantages of the balanced amplifier were given. The main advantages of the balanced amplifier over traditional amplifier are(1)improved input and output impedance matching, dynamic range, stability and reliability,(2) possible designing of the amplifier simultaneously for minimum noise figure and good input match.A LNA with the balanced structure was designed which conforms to WLAN IEEE802.11b. It not only meets the demand of gain and noise figure, but also has good input and output matching. To complete the design of the LNA, ATF54143transistor and ATF50189transistor which are manufactured by Avago Company,1P603S coupler made by Anren Microwave Company were used. With the help of Advanced Design System2009, an S-band LNA and its power supply circuits has been designed. And then the PCB of LNA was designed with Altium Designer Summer09and then processed. Finally, LNA DC operating point, S parameters and noise figure parameters were tested.