Design And Implementation Of CMOS Variable Gain Amplifier For DRM Receiver

With the popularity of digital technology, the fourth generation mobile communication technology, the Internet and so on, analog broadcasting is facing more and more severe challenges because of its inherent shortcomings. The best choice to overcome the disadvantages is to digitize the analog broadcasting. As a fastest growing digital broadcasting system standards, and the advantages of DRM (Digital Radio Mondiale) are providing listeners excellent audio quality along with the reduction of power dissipation and cost. So the research of DRM system is of great significance for the development of wireless communication in our country.In this paper, the design of variable gain amplifier (VGA) of RF-front end in the DRM receiver is presented. This paper only relates to CMOS technology for low power and low cost. The VGA should meet the following requirements:the relationship between the gains of the amplifier with control voltages should be dB-linear, the range of the gains should be wide, the VGA circuit has a high input linearity when the channel gain is low, and has a low noise figure when the channel gain is high. In order to extent the gain adjustment range of the VGA, the use of a series of Gilbert multiplier has been adopted, and the gain of VGA can be adjusted due to the change of tail current. To realize the relationship between the gains of the amplifier with control voltages be dB-linear, a circuit which generates voltage in the form of index is used.The Gilbert VGA is implemented in the process of SMIC’s 0.18-μm CMOS, and the layout has been finished. The post layout simulation results meet the design requirements.