Research And Design Of RF Front-end Architecture And Key Circuits For Non-contact Vital Signs Monitoring

Microwave radar vital signs sensing technology combines the emerging life sciences with the rapid development of microwave wireless communication technology,which is of cutting-edge innovation value.Due to its outstanding advantages of strong penetration,high detection accuracy and strong environmental adaptability,it is an important support technology for the new generation of biological detection and its intelligent analysis field,and is of great significance for the development of advanced technologies such as future intelligent medical,biological radar and security.With the rapid development of phased array,microelectronics and system on chip technology,the research of microwave vital signs sensing system and chip has gradually become one of the hot issues at home and abroad.Therefore,this paper focuses on the research and design of the RF front-end architecture and key circuit modules for non-contact vital signs monitoring.First of all,this article designs an RF front-end architecture based on the application scenarios and specific needs of non-contact vital signs monitoring.The double-sideband architecture is used to solve the zero point detection problem.The low-IF architecture is adopted to extract the motion signal from the mid-frequency domain instead of the baseband close to DC.It can achieve low DC offset and perfect I/Q balance to get better demodulation accuracy.The on-chip phase-shifting array is used to overcome the interference of random body motion on vital signs signals and the problem of multi-person detection phase conflicts.Secondly,this paper designs the system indicators through theoretical calculation and system simulation verification,and allocates them to each module reasonably.Based on this,the circuit structure of each module was designed and verified.Through the analysis of key performance parameters,appropriate optimization techniques were used to improve the circuit performance,so as to meet the design requirements of the overall index of the system.Among them,the voltage-controlled oscillator adopts a method of combining an analog tuning unit and a digital tuning unit to increase the tuning range,and uses a complementary differential structure and noise filtering technology to reduce phase noise.The mixer generates a low-frequency second-order intermodulation component through an external circuit to mix with the input signal,generates a signal with the same amplitude and opposite phase in the auxiliary path,and feeds it into the main path during the transconductance phase to eliminate the inherent three in the main path.The first-order intermodulation component and the second-order intermodulation component greatly improve the linearity performance of the mixer.The power amplifier solves the problem that the gate-source capacitance of the power tube in the output stage amplifying circuit changes with the input signal through the diode compensation structure to reduce the nonlinear effect in the circuit,thereby improving the linearity of the circuit.The low-noise amplifier uses noise cancellation technology to reduce the noise figure,and uses derivative cancellation technology to improve linearity.Balun reduces gain error and phase error through phase correction technology.The intermediate frequency voltage controlled oscillator adopts the structure of a four-stage differential ring oscillator,and replaces the mutual coupling pair with a CMOS latch,which solves the problem of unsynchronized changes in the voltage waveform of the output node.The intermediate frequency amplifier adopts a two-stage differential amplifier structure and uses negative feedback technology to improve linearity.The phase shifter uses the balun and quadrature signal generator to generate four quadrature signals,and then performs vector synthesis through an analog adder,and finally realizes a 360-degree uniform phase shift of the signal.All the circuits in this paper are designed based on tower Jazz 0.18 ?m Bi CMOS technology.The simulation results show that the performance of the system as a whole and each circuit module meets the design requirements.In the working frequency band of 5.2-6.2GHz,the input echo loss of receiver system is less than-17 d B,noise coefficient is lower than 5d B,and the gain reaches 63 d B;the maximum output power of transmitter system is 24 d Bm,the whole link gain is 33 d B,the output 1d B compression point is 25 d Bm,and the power consumption is 213 m W.The transient simulation shows that the waveforms of the IF output signal of the receiver and the RF transmission signal of the transmitter are accurate and stable in the time domain,which proves that the system has good performance.