A Research Of Key Circuits And Technology Of FMCW RF System

With the rapid development of millimeter wave technology,the size and the cost of microwave radar circuits has been reduced.In addition,with the in-depth research of radar systems,the types of radars are enriched,which makes the application of radar more and more widely.FMCW radar system usually has the advantages of low cost,simple system,small size,more available movement information,and small blind area at close range.It has been widely researched and applied in recent years.FMCW radar detects the motion information of a target by transmitting and receiving frequency-modulated continuous waves.Its main application areas include automotive radar,on-site rescue,smart home,medical care,and gesture recognition.This paper studies the key technologies in the FMCW radar system,designs and produces a FMCW radar front end working at 5.8GHz,and then processes the radar signal on the PC side to realize distance detection and vital signs detection.The main modules of the radar system include a sawtooth wave generating circuit,a voltage controlled oscillator,a power divider,a low noise amplifier,an IQ demodulator,and an automatic gain amplifier.The radar system can work in sawtooth frequency modulation mode and Doppler mode.The specific work of this article includes:This paper first introduces the system structure of FMCW radar and Doppler radar,receiving and transmitting waveforms and detection principles.The theoretical basis involved in vital signs detection is given for reference in system design.Then the scheme of the radar system is discussed,the transceiver link and chip selection are determined,so that the radar system index meets the application requirements.The circuit of each module is realized.In the design of the power divider circuit,a compact power divider is proposed.It combines the coupling line on the basis of the Wilkinson power divider prototype,which reduces the circuit's size.Finally,the radar signal is processed,the distance information of the main target is extracted from the baseband signal,the feasibility of FMCW radar for vital signs detection is discussed,and the Fourier transform,short-time Fourier transform,wavelet transform algorithm for heart rate extract.After testing,the radar system of this paper works stably,and successfully realizes the functions of distance test and heart rate test,with good accuracy.