The Design Of Low Power Automatic Gain Control Circuit Applied To Bluetooth Receiver

With the rising of smart devices and wearable devices,Bluetooth Low Energy has been widely used because of its advantages such as ultra-low power consumption,low complexity and low cost.Automatic Gain Control?AGC?circuit is an important module to expand the dynamic range of Bluetooth receiver.It is great significance to design a low-power fast-settling AGC circuit for a high performance Bluetooth receiver.A low-power AGC circuit for a Bluetooth receiver is presented in this thesis.The proposed AGC circuit is composed of a variable gain amplifier,a peak detector and a gain computation block,in which the variable gain amplifier includes four fixed gain amplifiers and one programmable gain amplifier?PGA?.A master-slave structure is adopted in the fixed gain amplifier to adaptively adjust the tail current source of the differential amplifier to maintain a constant gain with low power consumption.The PGA is made by the cascade connection of a transconductor and a transresistance amplifier,in which the transconductor can be changed by changing the resistance of the source degeneration resistor in the transconductance amplifier to adjust the gain with a gain step of 1dB.This structure of PGA can achieve good linearity performance at low power consumption.A novel peak detector composed of comparator and D flip-flop is also designed in this thesis,which is low-power and can detect the peak-signal level within 1?s.The gain control word is directly given according to the input signal strength,which saves power consumption of the quantization array.The gain computation block constructs a successive approximation algorithm by combinational logic circuit and sequential logic circuit to implement AGC.The proposed AGC circuit is designed and simulated in SMIC 0.18?m CMOS process.The simulation results show that the AGC circuit has a dynamic range of 14⁷0dB,a noise figure of 25dB,a bandwidth of11MHz,and IIP₃ of-45.8dBm and 13.3dBm for the highest gain and the lowest gain respectively.In addition,the AGC circuit converges to the desired level within 8?s.The whole AGC circuit draws a total current of about 970?A from the supply of 1.8 V,which meets the design specifications.