Design Of RF Front-End Low Noise Mixer Chip

The development and application of wireless communication technology and radar are inseparable from radio frequency transceiver system with superior performance.Mixer plays an important role as a module to realize frequency conversion in RF transceiver system.Noise,as one of the important indicators to measure the performance of the mixer,will directly affect the sensitivity of the receiver in the receiving link.The mixer under low noise will reduce the design pressure of the front stage LNA.In addition,in the direct frequency conversion receiver,the flicker noise introduced by the mixer is a very serious problem.Excessive flicker noise will obliterate the baseband signal,resulting in the inability to reconstruct the original signal.Therefore,the research and design of low noise mixer is of great significance.Firstly,this thesis investigates the research history and development status of low noise mixer at home and abroad.Then the basic knowledge of mixer design is introduced,including two common receiver structures,mixer working principle,common classification methods and performance indicators.Finally,two low-noise mixers are designed for different problems and application scenarios.Aiming at the flicker noise problem in the zero IF receiver,a high linearity and low noise mixer is designed using 65 nm CMOS technology.On the basis of the traditional active double-balanced mixer,the dynamic current injection technology is adopted to reduce the flicker noise introduced by the switch tube,the derivative superposition technology is adopted to improve the linearity of the mixer,and the impedance matching and single to differential function of the RF and LO terminals are realized through Balun.Through reasonable device selection and layout,the noise figure of the mixer is 10.9dB at 10 k Hz and 8.3dB at 100 MHz.The conversion gain is greater than 7.3dB in the operating frequency band,and the isolation from LO to RF is greater than 46 dBc.The input third-order intersection point is 0.1dBm.A low-noise mixer is designed for 5.8GHz radar system using GaAs HBT technology.The mixer is the first stage circuit of the receiving link.In order to achieve low cost,low power consumption and good noise performance,the mixer adopts an active singlebalanced structure.The transconductance stage improves the linearity of the mixer and reduces the design difficulty of the RF impedance matching network through source degradation inductance.After circuit simulation,the noise figure is less than 8.6dB,the static current is 3m A.The test shows that the small signal gain is 19.8dB,and the input1 dB compression point is-5.5dBm.Afterwards,based on the mixer used in the 5.8GHz radar system with a single module,a transmission line impedance matching network was designed to achieve impedance matching of the LO port.The simulation results show that when the power of the external LO signal source is greater than-6dBm,the small signal gain of a single module of the mixer is 23.5dB,and the noise figure is less than 7dB.Therefore,the single module of the mixer has been well optimized in terms of both gain and noise figure.