| In the wireless receiving system, the low noise power amplifier is used as the receiving front end, the noise and the gain characteristics are crucial to the whole receiver system. In wireless devices such as mobile wireless network, WLAN and radar system, the antenna receives the weak electromagnetic signal first through the low noise power amplifier. As an important part of RF system engineering application, the design of low noise amplifier has always been a hot research topic in the field of RF circuit. In this dissertation, based on the application of WLAN wireless system, through the analysis of the characteristics of balanced low noise amplifier, a low noise power amplifier system is designed, which is composed of branch line directional coupler. Specific research work is as follows:Firstly, through the analysis of the parameters of the power amplifier and the characteristics of low noise amplifier and drive, respectively, using ATF-54143 and ATF-50189, two high electron transfer rate of field effect tube, design the low noise amplifier and driver stage amplifier.Secondly, through the analysis of a variety of power synthesis technology, the overall structure of the system is designed by using the balanced structure. In the balanced structure, the consistency of the branch line coupler has an important influence on the output synthesis. Therefore, the design method of meandering, a miniaturized branch line directional coupler. The size of designed directional coupler is 0.18λ×0.13λ.Finally, the design of the low noise amplifier, drive power amplifier and miniaturization of sub regional coupler were processed. And they are tested by the Agilent N5227 A vector network analyzer. The test results show that the test results of the low noise amplifier, the drive power amplifier and the branch line coupler meet the design requirements. |
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