Research On S-band Two-stage Balanced Low Noise Amplifier

Wireless communication technique has become one of the main way to transmit information since the cellphone was invented.Such demanding drives the wireless communication technology develops rapidly.As the front-end module of the RF receiver system,low-noise amplifier(LNA)has been widely used in many kinds of wireless devices,such as mobile wireless devices,WLAN,radar systems and so on.Its main function is to amplify the signal received by the antenna while keeping the SNR as low as possible.The noise figure of LNA determines the sensitivity,and thus the performance of the wireless system.This thesis introduces a two-stage balanced low-noise amplifier with low noise figure,high gain,low input and output standing-wave ratio.The working frequency bandwidth is wireless network standard IEEE802.11 which covers 2.4 GHz ISM band,and we set the frequency band in 2.4 GHz~2.48 GHz.The RF characteristic as well as the development status of the passive and active components,the development history of transistors,the basic theory and improvement methods of low-noise amplifiers.Then the basic principle of two-stage balanced lownoise amplifier is introduced in detail,including the operating principle of 3d B directional couplers,the operating principle and characteristics of balanced amplifier.The two-stage balanced low-noise amplifier includes a low-noise amplifier,a drive amplifier at later stage,and a directional coupler.Then,the design process of two-stage balanced low-noise amplifier based on 3dB coupler is introduced,which includes the design theory and concrete work of each step.The simulation and optimization of the schematic and layout are carried out with Agilent's ADS software,and sent to the factory finally.And then we test the amplifier by using the vector network analyzer and noise figure meter,emphasizing the problems that we should pay attention to when testing,and show the test results.The results of each part of the test are basically meet the design requirements.Finally,the paper analysis the results,and so does the unsatisfactory results,and propose improvements.