Design Of CMOS Down-conversion Mixer For Sub-8GHz UWB RF Receiver

With the continuous improvement of people’s requirements for the communication system,the communication technology is constantly changing.The research and design of ultra-broadband（UBW）RF receiver and its modules with higher frequency and wider coverage has become a hot spot.Down-conversion mixer is the key module in the receiving link,which greatly affects the overall performance of the receiver,and it is also the focus of research and design.With the application of the 5G,the spectrum resources of higher frequency band are gradually developed,and the research on Sub-8GHz UWB RF receiver is based on this.Under this background,this thesis studies and designs a UWB RF receiver down-conversion mixer suitable for 75MHz～8GHz by using 65nm CMOS technology.The mixer adopts passive current mode structure.The core circuit includes transconductance,switch,transimpedance amplifier and orthogonal local oscillator generation circuit with 25%duty cycle.There is no direct current in the switch tube,which reduces the flicker noise to a great extent;The front stage is transconductance,which adopts current reuse technology and self bias technology to convert voltage signal into current signal,reduce power consumption and increase transconductance value at the same time;The transimpedance amplifier realizes the conversion from current signal to voltage signal,plays the role of LPF,and the adjustable feedback network can adjust the gain;The 25%duty cycle orthogonal local oscillator generation circuit makes the switch stage without on/off overlap,and improves the gain and linearity.In this thesis,the circuit design schematic diagram,pre-simulation,layout design and post simulation of the down-conversion mixer are given in detail.The post simulation results show that the mixer can realize（10d B/16d B/22d B）gain adjustment under 1.2V power supply voltage,and the IIP₃ is 2.73～3.41d Bm,The double sideband noise figure is 11.90～12.54d B,the isolation is>45d B,the overall power consumption is 8.7m W,and the layout area is 855μm×655μm。The down-conversion mixer of UBW RF receiver designed in this thesis has good performance in the frequency range of 75MHz～8GHz,meets the performance requirements.