Research Of Key Technologies Of 24GHz Dual-mode Millimeter-wave Radar Receiver Front-end

MMW technology has the advantages of high detection precision and strong permeability for non-conducting materials.It is crucial in vital industries such as ultra-high-speed communications,high-precision radar detection,passive imaging,medical treatment,and transportation.MMW Radar can be used to detect,locate and image moving objects,and is less affected by external factors such as weather.Combined with low-cost,highly integrated CMOS technology,in recent years mm W radar has gotten a lot of interest.This article focuses on the 24 GHz millimeter-wave radar for short-range target detection.The design and tapeout of a 24 GHz high-performance dual-mode millimeter wave radar receiver,which can be used for the automation and interaction of consumer products are completed.The test and subsequent improvements to the chip are completed,the main research results are as follows:(1)Completed the key technology research of the 24 GHz dual-mode millimeter wave radar receiver.Firstly,the 24 GHz FMCW/Doppler dual-mode mm W radar chip integrates two radar systems.The Chip transmits linear sweep signals to achieve the measurement of the target's speed,distance and angle in FMCW mode,and its measurement is fine.The chip only transmits one single-frequency signal in Doppler mode,speed information is obtained.And subsequent digital signal processing is simple,which is very advantageous when detecting the real-time motion state of an object.Secondly,for the 24 GHz dual-mode radar receiver in the presence of TX?RX leakage,the noise problem at the ultra-low frequency is analyzed from multiple dimensions.The analysis of the noise contribution mechanism can be summarized in three aspects:RF path flicker noise up-mixing,LO path flicker noise up-mixing,leakage causes additional DC current in the switch tube.In addition,the study considers the effect of the RX gain fluctuation and the TX output power in the sweep frequency range,mainly including low-frequency interference and amplitude modulation sideband interference of useful signals.(2)Completed the design of the 24 GHz dual-mode millimeter wave radar receiver.To solve the noise problem at the low IF of the 24 GHz dual-mode millimeter wave radar receiver,a multi-dimensional noise optimization strategy is proposed.For RF path,one stage common source with source degeneration inductance structure is used,and a neutralizing capacitor is added to offset C_gs.The introduction of source degeneration inductance reduces the equivalent transconductance of the RF path and reduces noise.For the LO path,the Mixer-Like idea is used to design a low flicker noise contribution buffer circuit.The LO signal input tube can be equivalent to a Mixer switch tube.The flicker noise self-circulates when it is in the on state,and it does not contribute to the off state.The Mixer-Like Buffer noise contribution accounts for only 6%,which significantly improves the LO path noise.For the mixer switch tube,the passive structure is combined with the 8bit R2R DAC to provide the optimal bias,which can obtain the optimal noise bias under different PVT conditions,and has high robustness.(3)Completed the tapeout and test of the 24 GHz dual-mode millimeter wave radar receiver.The above chip is based on 55 nm CMOS process design and tape-out,and the single-channel RX area is 0.78 mm*0.89 mm.The measurement results show that P_DC=30 m W.S11 is less than-10 d B@23.5?27.0 GHz.TX is off in FMCW mode when there is no TX-RX leakage,CGmax=18.1 d B@24.56 GHz,in the frequency range of23?24.6 GHz,CG>12 d B.The LO signal is 23 GHz,23.72 GHz and 24.2 GHz,NF is less than 13 d B@8.3 k Hz?166 k Hz.TX is on,when TX-RX leakage occurs,CGmax=17.46 d B@24.32 GHz,CG>12 d B in the frequency range of 23?24.6 GHz.The LO signal is 23 GHz,23.72 GHz and 24.2 GHz,NF is less than 19 d B@8.3k Hz?166 k Hz.In Doppler mode,when TX is off,CG=18.85 d B@24.125 GHz.At24.125 GHz,the optimal NF value is 9.2 d B@400 Hz.When TX is turned on,CG=18.27 d B@24.125 GHz.At the frequency of 24.125 GHz,the optimal NF value is23.67 d B@900 Hz.(4)Completed the improved design of the 24 GHz dual-mode millimeter wave radar chip.Firstly,the design of the 24?26.5 GHz broadband dual-mode millimeter wave radar receiver that can achieve higher range resolution is further completed.A broadband input matching design based on CPW and Bondwire is adopted,CPW and Bondwire are modeled through HFSS,and the on-chip balun is combined to complete broadband matching.For a high quality signal,a wideband resonant network based on varactor tuning is proposed to diminish the gain variations of RX,so that the gain fluctuation of the receiver is less than 1 d B in the swept frequency bandwidth.Aiming at the quadrature LO signal,a low-loss broadband IQ two-way differential signal generating circuit is presented.Secondly,completed the layout design of the 24?26.5 GHz broadband dual-mode millimeter wave radar receiver and the post-simulation of five corners and three temperatures.Considering that the isolation between TX and RX is 25 d B,the leakage signal of TX?RX is simulated.The post simulation results show that at TT 40?and FMCW mode,CG_max=17.04 d B@24.9 GHz,and the conversion gain fluctuation of the receiver in the frequency range of 23.5?27.6 GHz is less than 1 d B.NF=14.85d B@f _IF=8.3 k Hz,NF=11.08 d B@f _IF=166 k Hz.In Doppler mode,CG=17.63d B@24.125 GHz,NF=34.74 d B@f _IF=10 Hz,NF=11.08 d B@f _IF=1 k Hz...