Research On CMOS Low Voltage High Linearity Mixer

With the dramatic development of SLSI and microelectronics, communication technology has gained unprecedented progress. There is no doubt for that wireless communication as a part of communication achieves the greatest progress. CMOS radio frequency front-end is made up of receiver and transmitter, as a key part of which, the performance of mixer greatly determines the performance of the entire front-end.On the other hand, while communications technology is exploding. Due to that Wireless communication can compensate the shortcomings of the Wire Network it is enjoyed in personal and commercial field. To satisfy the growing demands of users, Wireless communication is developing towards to lower dissipation and better performance. It has been a tendency that RF front-end and digital baseband integrate on a chip. At present, the digital baseband can be worked at a very low voltage, which is not suit for RF front-end. At the same voltage with digital baseband, the linearity,working frequency and gain of RF front-end will be limited. Due to that, to design low voltage high linearity RF front-end becomes a key problem in the RF intergrate circuits. Mixer as a key part of RF receiver has gained increasing interesting on low voltage and high linearity.Firstly, this paper introduces the principle of RF circuits. Then summarize the progress and unsolved problems in the design and researcher of CMOS mixer,in which most work focus on low voltage and high linearity aspects. The main achievements are as followings:1) A mixer working at 1V low voltage was presented after analyzing the current low voltage CMOS mixer. The proposed mixer can work at low voltage because there is only one MOSFET in the transconductance stage. The simulation results indicate that the proposed circuit has good performance.2) A modified MOSFET transconductance linearization technique is proposed to improve the linearity after analyzing two nonlinear analysis methods and current linearity improvement methods. Simulations show that the using of modified MGTR technique achieves as much as 8 dB IIP3 improvements without sacrificing other features such as noise figure, power consumption and gain.3) The linearity influence of mixer caused by switch stage is analyzed. Simulations show that properly DC bias improves the linearity of mixer.Lastly, summary of previous work and suggestion for future research are given.