Microwave Radiometric Imaging Of Tilting Mirrored Aperture Synthesis

In the earth observation,aperture synthesis(AS)forms a large physical observation aperture by a thinned array of small-aperture antennas.AS has the advantages of reducing antenna size and covering a large field of view without mechanical scanning.However,the AS system is too complicated to further improve the spatial resolution.Mirrored aperture synthesis(MAS)was proposed to achieve higher spatial resolution without extending the size of the antenna array.However,the MAS principle suffers from a lack of experimental validation.Moreover,the refelector of the MAS is perpendicular to the plane of the antenna array,and this vertical structure causes some problems: the field of view(FOV)of MAS can not be adjusted and MAS needs more antennas with limited inprovement in spatial resolution.Based on this vertical structure,MAS is termed as vertical mirrored aperture synthesis(VMAS)in the thesis.In the thesis,the principle of MAS is verified firstly.Then tilting mirrored aperture synthesis(TMAS)is proposed to improve the performance.More specifically,TMAS is proposed to adjust the FOV.On this basis,tilting mirrored aperture synthesis with multiple reflections(TMAS-MR)is proposed to increase the mirrored antennas,thus improves the spatial resolution further.Tilting mirrored aperture synthesis with multiple angles(TMAS-MA)is proposed to obtain more cross-correlations,thus reduces the antenna.The main innovative work of the thesis is presented as follows:1)The experimental verification of the VMAS principle and problem analysis.The VMAS principle has not been sufficiently validated by practical experiments.To solve this problem,firstly,an innovative experiment system of MAS at the V band(MAS-V)is designed.Then the experiments are carried out to verify the principle of VMAS,including the experiments on the interference fringe pattern,spatial resolution,moving reflector,as well as imaging of natural scene.The experimental results demonstrate VMAS can achieve two times as much of spatial resolution as AS.Then the problems of VMAS are analyzed.2)Tilting mirrored aperture synthesis(TMAS)is proposed.The principle formula is derived.The relationship between the tilting angle of the reflector and the FOV is analyzed.The conclusion is proved that VMAS is a special case of TMAS when the tilting angle of reflector is 0°.Simulation results demonstrate the validity of TMAS.3)Tilting mirrored aperture synthesis with multiple reflections(TMAS-MR)is proposed to improve the spatial resolution.The principle formula is derived.TMAS-MR combines the antenna array and the tilting reflectors to make the equivalent array larger,thus improves the spatial resolution.Then the simulation results and experimental results show that TMAS-MR can achieve at least three times as much of spatial resolution as AS with the same array size.4)Tilting mirrored aperture synthesis with multiple angles(TMAS-MA)is proposed to reduce the number of the antennas.The principle formula is derived.Multiple equations are combined to form a larger system equation by changing the tilting angle of the reflector,therefore TMAS-MA can reduce the number of the antennas.The theoretical analysis and simulation results demonstrate that TMAS-MA can reduce remarkably the number of the antennas and TMAS-MA with only one antenna can also reconstruct the brightness temperature image.