Study On Key Technologies Of Super-resolution Imaging Of Millimeter Wave Radar

Radar is an electronic device which uses electromagnetic wave to detect target.It radiates electromagnetic wave to space in a directional way and receives echo reflected by target in space,then calculates direction,distance and velocity of target.Therefore,radar has a wide application scenarios in detection and perception.Millimeter wave radar is a radar working in millimeter wave section.Because the working wavelength is shorter than microwave radar,it can provide higher imaging resolution;meanwhile,with the active detection method and the physical characteristics of electromagnetic wave,it can work stably in smoke,haze,darkness,strong light and other environments,and has strong environmental adaptability.However,due to the limit of Rayleigh,conventional millimeter wave radar has difficulties in further improving the angle resolution of imaging,which restricts the wide application of millimeter wave Radar in the field of sensing imaging.Therefore,in order to improve the angular resolution of millimeter radar,the aim of this paper is to realize the super-resolution angle measurement of the target by using multi input multi output(MIMO)technology and the direction of arrival(DOA)estimation algorithm in array signal.The main research work includes:(1)The principle of range,speed and angle measurements of frequency modulated continuous Wave(FMCW)Radar based on sawtooth modulation is studied.And concludes that the angular resolution is a key factor affecting the imaging resolution of millimeter wave radar.In order to improve the angle resolution of millimeter wave radar,the MIMO technology using virtual array element to enlarge the array aperture is studied,and the signal model of time division multiplexing(TDM)MIMO Radar Based on FMCW transmitting waveform is established.(2)In order to further improve the imaging resolution of millimeter wave radar,the common DOA algorithms,such as Capon,MUSIC,Root-MUSIC and ESPRIT algorithm are introduced.According to the signal model of TDM MIMO radar,the DOA algorithms of TDM MIMO radar are simulated and compared.Two decoherence algorithms,forward and backward spatial smoothing and improved MUSIC,are compared and analyzed.Based on forward backward spatial smoothing algorithm and root MUSIC algorithm,this paper proposes a decoherent unitary root MUSIC algorithm and carries out simulation experiments.The experimental results show that the algorithm can not only reduce the calculation time,but also has superior decoherence performance.(3)The range-angle two dimensional imaging signal model of millimeter wave radar is studied.Based on the signal model,a two-dimensional imaging algorithm combining discrete Fourier transform(DFT)ranging and the decoherent unitary Root-MUSIC algorithm for angle measurement is proposed.Then,the hardware platform and related parameters of the millimeter wave radar are introduced,and the signal processing flow of the range angle two-dimensional imaging algorithm proposed in this paper is given.Finally,experiments are carried out in outdoor and indoor scenes using millimeter wave radar hardware platform,verified the performance of the proposed range-angle two dimensional imaging algorithm in decoherence and super-resolution angle measurement.