Design Of Millimeter Wave Down-conversion Mixer Based On Ka/E Bands

With the rapid development of millimeter-wave technology,77GHz automotive radar,a key sensor in assisted driving,is receiving widespread attention from academia and industry.At present,due to the maturity of silicon-based technology,the corresponding transistor characteristic frequency can also meet the design requirements of integrated circuits at 77GHz.Compared with millimeter-wave automotive radar front-end chips based on III-V compounds or silicon-germanium processes,silicon-based technology has the advantages of low cost and easy integration.Therefore,the silicon-based automotive radar chip in the 77GHz band is a hot research spot at present.As a key module in the millimeter-wave automotive radar chip,the design of the down-conversion mixer largely determines the performance of the system.Based on this,this dissertation has conducted in-depth research on the down-conversion mixer in 77GHz automotive radar chips.The main research contents are divided into the following two parts:（1）Research and design of 77GHz active down-conversion mixer.In order to improve the linearity of the traditional Gilbert mixer in the millimeter wave band,the resistance load of the mixer is analyzed and improved.Based on the analysis of the mixer mixing principle,the dissertation focuses on optimizing the size of the switching transistors and the gate bias of the switching transistors.At the same time,the RF and local oscillator transformers are analyzed and optimized in the layout design.This chip was fabricated in 40nm CMOS process.The operating frequency of the down-conversion mixer is 76-81GHz,and the voltage conversion gain is 5.7dB.At center frequency of 78.5GHz and intermediate frequency of 10MHz,the input P_1dB is 0.8 dBm.Power consumption of the mixer is 1.5mW.（2）Research and design of 77GHz passive down-conversion mixer.In order to solve the problem of low frequency flicker noise of radar receiver,a passive down-conversion mixer is designed.By using self-biased transimpedance amplifier to bias the source and drain of the mixer,the coupling capacitance between stages is removed.By analyzing the effect of transistor parasitic PN junction on voltage and current,the linearity of the mixer is effectively improved.This mixer was also fabricated in 40nm CMOS process.The post simulation results show that the mixer’s voltage conversion gain is 5～5.7dB in the whole frequency band,with the single sideband noise figure 17.5～18.8dB.At center frequency of 78.5GHz from 76～81GHz with 1.3dBm input P_1dB @50MHz IF.