The Analysis Of Thermal Noise Characteristics Of The RF Front-end In Receivers

The research of thermal noise is a subject of great importance in many areas. This paper analyses the noise characteristics of the RF front-end of receivers. It studies the key technology of the low noise design in the RF front-end of receivers.At the first, it introduces the basic theories of electronic noise, and set up a general model of receivers. An improvement is given in this paper on the definition of the DSB noise figure of mixers, in which the Double Side Band (DSB) noise figure among signal frequency is distinguished from the one among image frequency. Basing on the model made in this paper, an expression of the noise figure of the RF front-end is pushed over. Beginning with the expression of the noise figure of the RF front-end, key technologies of the low noise design is studied.For low noise figure, several points are made clear in the process of gain distribution. In the RF front-end, the function of the Low Noise Amplifier (LNA) is to amplify signal power and introduce the least noise at the same time. The paper come out of some conditions at which the LNA can function effectively.Image rejection can reduce receiver's SSB noise figure. Former articles seldom analyzes the good effect of the image rejection on SSB noise figure quantificationally, however, it is deeply analyzed in this paper, a method to ascertain the image rejection ratio is built.This paper studies the path of integrating large dynamic range and low noise figure in one receiver. Particularly, the noise characteristics of Variable Gain Amplifier (VGA) is analysed.In the end, the design of an RF front-end in receiver is finished. Measurements results validate the adopted low noise design approach.