Research And Design Of Ka Band Passive Millimeter Wave Imaging Antenna

All the objects in nature radiate electromagnetic waves spontaneously.Passive millimeter wave(PMMW)imaging system works exactly by detecting millimeter waves radiated from an object,which has been widely used in the detection of hidden objects and security inspections.The PMMW imaging antenna system is composed of feed antenna and focusing antenna,the latest researches of which have manily focused on the miniaturization and high gain of the feed antenna,high resolution of the focus antenna.The main work carried out in this thesis is as follows:Firstly,In order to achieve the miniaturization,high gain,and low sidelobe of the feed antenna for the Ka-band(30?40 GHz)passive imaging system,pyramid horn antenna and cone horn antenna are designed in this thesis.Both of them have higher return loss and good radiation characteristics but with larger diameters,which is not suitable for millimeter-wave imaging systems during low frequency band.Furthermore,a novel antipodal linear tapered slot antenna(ALTSA)is designed.The gain of which is improved by loading metamaterial structure in the front of the antenna and the broadband characteristic is achieved by substrate integrated waveguide(SIW)feed.The simulation and measured results show that the proposed antenna display good impedance characteristic and a high and stable gain(about 16 d Bi),that is the S11 of the antenna is less than-10 d B during the whole band(30?40 GHz).Meanwhile,the antenna has a small size,which can meet the requirements of the small diameter of the feed antenna for PMMW imaging system.Secondly,by combining the Gaussian quasi-optical theory with geometrical optics knowledge,quasi-optical path is analyzed and a high-resolution hyperbolic dielectric lens is designed with a caliber of 500 mm.The simulation results are in good agreement with the theoretical calculation values.Based on this,the design of the focal plane feed antenna array and the joint simulation with the lens was completed.The simulation results show that the focal plane antenna array can achieve a 51 mm focal spot on the object plane and the focal spot interval is about 50 mm,which has a high spatial resolution.Finally,in order to solve the defects of the large volume and difficult processing of traditional dielectric lenses,the metasurface lens is researched.A high-resolution metasurface lens based on the incidence of plane wave is designed by the metasurface unit with polarization insensitivity and coaxial annular structure.the is Then,a highresolution metasurface lens is designed by referring to the design method of near-field focusing media lens,which can realize near-field focusing.The lens with high spatial resolution has a 3d B focal spot diameter of about 9mm at 70 mm away from the lens,which can be used to achieve the miniaturization and high-resolution imaging of PMMW imaging system.