Research On Millimeter Wave Radar Imaging Method Based On Metasurface Aperture

There are two types of active radar imaging systems,namely synthetic aperture radar(SAR)imaging system and real aperture radar imaging system.Synthetic aperture radar system imaging is to form a large-sized virtual aperture through the relative movement between the radar and the target,thereby achieving high resolution in azimuth.The metasurface aperture radar imaging system is a new system of real aperture radar imaging system.Through the design and optimization of the metasurface aperture resonance unit,it has a powerful spatial modulation capability for electromagnetic waves.Under the excitation of electromagnetic signals of different frequencies,randomly changing spatial radiation field can be generated to realize the detection of target scene.Due to its advantages of small size,low cost,low system complexity,and all-weather,metasurface aperture imaging radar will have a wide range of future such as missile seeker forward-looking imaging,unmanned platform environmental perception and planetary detector environmental perception.The distinguishing feature of the metasurface aperture imaging radar system is the powerful control ability of the electromagnetic metasurface to electromagnetic waves.Under the excitation of electromagnetic signals of different frequencies,it can generate a randomly changing pattern in space to illuminate the target scene and receive the target scattered echoes.Realize the acquisition of target scene information.The number of measurement modes that can be generated is limited due to the size of the metasurface aperture resonance unit and the operating bandwidth of the system.Therefore,metasurface aperture radar imaging needs to solve the ill-conditioned inverse problem of solving a large number of unknown parameters from a small number of observations.The main research content of this article is the basic theory and algorithm of metasurface aperture radar imaging,the construction of metasurface aperture radar imaging system and the processing analysis of measured experimental data.The article does not do too much research and elaboration on the specific design simulation of the metasurface aperture,the specific research content includes the following aspects:(1)Basic theory of metasurface aperture radar imaging: including the frequency sensitivity characteristics of the aperture resonance unit,the mechanism of the metasurface aperture generating a random radiation field in space,and the mathematical principle of the metasurface aperture detecting the imaging scene.(2)Metasurface aperture radar imaging algorithm: The principle of Orthogonal Matching Pursuit(OMP),Sparse Bayesian Learning(SBL)and Complex Approximate Message Passing(CAMP)three compressed sensing sparse reconstruction algorithms are introduced,and algorithm simulation analysis and algorithm performance comparison are made.(3)According to the characteristics of the metasurface aperture radar system used in this paper,the principle of metasurface aperture to achieve super resolution is studied,and a three-dimensional imaging method of super surface antenna based on chirp signal is proposed.First,the principle and formula of the proposed algorithm are introduced.The proposed algorithm first estimates the distance of the three dimensional scattered echo signal and solves the target signal power;according to the set power detection threshold,the target signal power is detected and the orientation is reconstructed Pitch the twodimensional frequency domain echo;combine the metasurface frequency sensitive pattern matrix to complete the reconstruction of the frequency domain echo,and finally realize the three dimensional target imaging reconstruction.Then,a measured imaging experiment with five corner reflectors as the target scene is designed.The experimental results show that the proposed algorithm effectively reconstructs the target and achieves 5 times angle super resolution,and also verifies that the metasurface aperture radar generates random radiation in space.The proposed algorithm achieves dimensionality reduction imaging calculation during the reconstruction process.Compared with most existing algorithms,such as three-dimensional compressed sensing and distance decoupling,the calculation complexity is reduced and the target resolution is improved.(4)The construction of the metasurface aperture radar imaging system and the analysis and processing of the measured imaging experiment data: first,a brief introduction to the metasurface aperture radar imaging system used in this paper;then,a three-dimensional target scene imaging experiment is designed,and finally several the imaging algorithm processes and analyzes the echo data.