A48dB-Dynamic Gain Range,37dBm-ⅡP₃CMOS VGA Design

With the increasing demand of communication market, the RF communication system isdeveloping to higher integration, higher performance, and lower power consumption. As avery important part of wireless receiver, the variable gain amplifier has drawn much attentionamong researchers in this area. Due to problems the RF signal meets (such as attenuation andenvironmental noise) when it transmits in air, the quality of signal decreases and its amplitudemaybe very large or very small, which cause a great trouble for receivers to demodulate.In this dissertation, the design of variable gain amplifier has been discussed. Firstly, thisdissertation introduced wireless receiver and VGA’s function in a wireless receiver system.Second, common structure, theory and parameter of VGA are discussed. Then based on theintroduction above, a VGA system controlled by6bits digital signal is designed. The VGAproposed is designed in TSMC0.18μm CMOS process which has character of high gaindynamic range, high linearity and low power. The fine VGA is based on a new exponentialapproximation which is a combination of pseudo-exponential and Taylor series approximationtheory. At the same time, the proposed VGA integrated DCOC module and digital controllermodule which means it can directly convert digital controlling signal to specific gain. At last,some design rules in layout are mentioned and the overall layout is proposed.