The Research And Design Of High Linearity Mixer For RF Front-End

With the rapid development of wireless communication network,the performance of wireless communication equipment put forward higher requirements,high-performance wireless receiver RF front-end urgent need.In the RF receiver front end,mixer is a key module,its linearity determines the dynamic range of the receiver,so the research of high linearity mixer has become the focus of the study of RF receiver system.In general,the DC power consumption of the mixer increases with the increase of the dynamic range of the mixer.Therefore,how to improve the linearity of the mixer on the basis of low power consumption,while taking into account the other performance,is the difficulty of mixer design.This paper first describes the important use of GPS satellite navigation and WLAN 802.11 b/g standard non-cellular wireless communication in social life,and introduces the present research situation of mixer at home and abroad.Then,the conversion gain,noise and linearity of Gilbert mixer are analyzed in detail,and the optimization techniques to improve these properties are analyzed in detail.Finally,based on the theoretical,the paper had completed the design and simulation of the following two kinds of mixers by using the TSMC 0.18um CMOS RF technology:(1)A radio frequency front-end down-conversion mixer for GPS satellite navigation is studied.The circuit is mainly through the use of derivative superposition(DS)technology,improved dynamic current injection technology,RC network load technology to improve the linearity of the mixer and reduce noise.This is designed to work in GPS LI band 1.575GHz,circuit simulation results:the power supply is 1.8V,the conversion gain of 13.IdB,input three-order intercept point(IIP3)is 4.4dBm,the noise figure is 7.45dB,the power consumption of the circuit is 7.2 mW.(2)A high linearity CMOS mixer is studied for 2.4G WLAN.The design innovates a third-order transconductance coefficient correction of current mirror circuit that effectively improves the linearity of the mixer and increased the degree of freedom of design;using current injection technique to improve the noise performance of the switch stage;the source inductor feedback technique to matching the RF input port and improve the linearity.The circuit operates at 1.8V,the voltage conversion gain is 14.6dB,IIP3 is 12.69dBm,the noise figure is 7.13dB and the power consumption of the circuit is less than 8 mW.