Design And Study Of AGC Based On SoC Of The Internet Of Things

The Internet of Things refers to uniquely identifiable objects (things) and their virtual representations in an Internet-like structure. Radio-frequency identification (RFID) is often seen as a prerequisite for the Internet of Things. The performance of RF receiver directly determines the efficiency of its work. An excellent variable gain amplifier of an automatic gain control circuit could make a RF receiver work well. A novel exponential approximation function and an all-CMOS VGA (Variable Gain Amplifier) design for the SoC of the internet of things is presented in this paper.As an all-CMOS implementation, there are two approaches used to realize VGAs depending on whether the control signal is digital or analog. The digitally controlled VGAs use a series of switchable resistors or switched-capacitor techniques to control gain. In digitally controlled VGAs, gain varies as a discrete function of the control signal, which can lead to discontinuous signal phases that can cause problems in many systems. In order to reduce the amount of jumps, a large number of control bits are required with digitally controlled VGAs. Therefore, for applications that require smooth gain transitions, the VGAs controlled by analog signal are preferred. The VGAs controlled by analog signals typically adopt variable trans-conductance or resistance stages for gain variation. With these topologies, the gains can be controlled continuously, but obtaining a wide exponential gain variation as a function of control voltage is a big issue, especially in CMOS technology.The ideal features of VGA include a wide range of gain variation, low-power consumption, small chip size, and controllable dynamic gain range. The design of a two-stage VGA is designed in0.18-μm CMOS technology is proposed. It shows a max gain variation of more than70dB and a60dB linear range with linearity error of less than±3dB. The variable gain range can be controlled from-34to32dB. The3-dB bandwidth is from132MHz (at maximum gain of34dB) to0.91GHz (at minimum gain of-32dB). The VGA dissipates less than1.1mA with1.8V power supply while occupying0.04mm2of chip area excluding bondpads.