| Space remote sensing technology has made great progress after rapid development in recent decades.Among many remote sensing equipment for ground imaging,optical remote sensing camera and synthetic aperture radar are the two most commonly used equipment.Judging from the research trends of various countries at this stage,comprehensive observation equipment with multi-band and multi-mode observation capabilities has become a key research direction in the field of space remote sensing in the future.The integrated imaging equipment of optical remote sensing camera and synthetic aperture radar is one of them.The advantages of optical remote sensing cameras are that they have high observation resolution,rich images and easy viewing by human eyes,while synthetic aperture radar has strong adaptability to the environment and can observe all day and all weather.The combination of the two will give full play to the advantages of the two devices,the combined integrated equipment can obtain optical and radar images of the same time phase,and its comprehensive observation ability and environmental adaptability will be greatly improved.At present,there are very few research results on the integrated imaging equipment of optical camera and synthetic aperture radar in the world,and there are still many gaps to be filled in this field.Therefore,it is of great significance to promote research in this direction.On the basis of fully investigating the domestic and foreign research status and scientific research achievements,this dissertation has completed the analysis and design of the integrated imaging system and the research of the band separation device.Finally,the principle prototype is built,and some performances of the system are verified through experiments.The main research work of this dissertation is as follows:This dissertation firstly studies and compares the system composition and structure types of optical remote sensing camera and synthetic aperture radar,and analyzes and calculates the constraints of the integrated design of the two devices.On this basis,a new integrated design is proposed.The integrated scheme is based on the off-axis structure,the visible light and microwave share the primary and secondary mirrors,and the dual parabolic reflector antenna design is adopted.In this dissertation,the actual design of the system is carried out.The proposed satellite orbital altitude is 496 km,the system aperture is 2700 mm,the focal length of the optical system is 34206 mm,the field of view is 0.1°×0.71°,and the final average MTF value of the optical subsystem at 50lp/mm basically reaches 0.47,The azimuth ambiguity of the SAR subsystem is better than-20 dB,the range ambiguity is better than-22 dB,and the NESZ is better than-16 dB.Moreover,the directional pattern is good.Secondly,this dissertation proposes four band separation device schemes for reflecting microwaves and transmitting visible light,which are ITO transparent conductive film,graphene film,nano metal wire film and metal grid film.After analyzing and comparing the characteristics and optoelectronic properties of each scheme,ITO transparent conductive film and metal grid film were finally selected as the alternatives for the band separation device.In this dissertation,the electromagnetic shielding characteristics of the two alternative schemes are theoretically studied and their actual spectral frequency division effects are tested experimentally.Finally,the microwave reflectance of the ITO test piece in the Ka band is 50%,and the average transmittance in the visible light band of 400-760 nm reaches 97.9%.The average transmittance of the 160μm-spaced grid-shaped metal grid test piece in the visible light band of 400-900 nm is 87.1%,and the average reflectance in the Ka band is about 43%.The average transmittance of the grid-shaped metal grid test piece with an interval of400 μm is about 90% in the visible light band,and the average reflectance in the Ka band is about 42%.In addition,this dissertation proposes an improved crack template metal grid based on the grid-type metal grid,which can effectively reduce the diffraction effect of the grid-type grid.After testing,the average reflectance of the crack template metal grid test piece in the Ka band is higher than 94%,and the average transmittance in the visible band is 86%.Since the optical primary and secondary mirrors will be used as radar antennas,this dissertation proposes a scheme of using an aluminum-based silicon carbide substrate with nickel-coated aluminum film to ensure the high reflectivity of the primary and secondary mirrors in the optical band while improving their reflectivity in the microwave band.After experimental tests,the average reflectivity of the test piece in the visible light and near-infrared bands is 95.9%,and the average reflectivity in the microwave band is higher than 98%.In addition,this dissertation proposes to use quartz/cyanate composite material as the wave-transmitting structural material to improve the microwave space propagation characteristics.After testing,the average transmittance of the wave-transmitting test piece in the Ka band reaches 78%.Finally,the experimental principle prototype with a diameter of 215 mm is designed and processed in this dissertation.The principle prototype has the same optical-mechanical structure as the spaceborne system,which can better reflect the performance of the spaceborne system.In this dissertation,the beamforming ability and microwave loss of the principle prototype are actually tested in the laboratory environment.The simulation results of the final principle prototype pattern are in good agreement with the test results,the main lobes basically coincide,and the measured microwave loss is 0.98.dB,less than 1dB,the effect is good. |
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