| In recent years, with rapid development of the RF technology in the communicationsystems, higher demands on the RF receiver has been made. It is significant to makeresearch on the RF receivers and design some new RF receiver with higher integrationdensity and lower power consumption. Low Noise Amplifier (LNA), one of the mostimportant parts in the RF circuit, is designed as the front end circuit to amplify the desiredsignal. To ensure the performance of the whole receiver system, the noise factor of the LNAshould be lower enough and the power gain should be higher enough to overcome the noisecaused by the post processing module.The classical theory of noise about the two-port network and the principle of the LNAare firstly introduced in this thesis; the generation mechanism of the noise from inside andoutside system is analyzed. The mathematical model of noise caused by the transistor in theLNA and the rationality of selected transistor in this thesis has also been researched. TheEM Simulation Software, Advanced Design System, is employed to design and optimizethe LNA circuit. The topological circuit of the selected transistor has been designed afterobtaining the quiescent operating point. The optimized circuit can work steadily at thefrequency of2.0GHz to3.0GHz. The characteristic of the matching network which isrequired by LNA is analyzed and the matching circuits of it are designed in this thesis. Withthis matching network, the input noise is lower enough matching the performance index;the output power gain reaches the maximum at the same time. The noise factor of LNAdesigned in this thesis is1.649dB, and the power gain is16.917dB.Several methods which are employed to research the linearization techniques of LNAhave also been contrasted with each other in this thesis, such as Feed-forward method,Negative feedback method, and Pre-distortion method. A circuit has been designed toensure the working stability of the power tube MRF9045N at the last. |
