Study Of Coupled Models Between Fields Of Structural Displacement And Electromagnetism And Their Analyses Of Antennas

As a kind of electromechanical system, electronic equipments have serious electromechanical coupled problems, which constrain the improvement of the actual electromechanical equipments and the development of the next generation equipments. With the support of several national key projects, this paper studies the coupled problem between structural displacement field and electromagnetic field, which mainly takes place on the design and analysis period of reflector antennas and planar slotted waveguide array antennas. The modeling and synthesis analyses of the coupled problems are studied in detail. The author's major contributions on the subject can be summarized as follows:(1) The electromechanical coupled field problem of the reflector antenna is studied, and an electromechanical coupled model of the antenna is acquired to relate the structural displacement field with the electromagnetic field. In the model, the structural displacement field is a kind of system errors including the errors of main reflector, the position and orientation of the feed. The random errors from the process of manufacture and assembly of the antenna are considered in the model too. These errors change the amplitude and phase distribute of antenna aperture to affect the far electric field of antenna. For the non-matching grids problem of structure and electromagnetism in the solution of the coupled field model, the transformation matrix between two grids is used. The deformation experiment of a cassegrain reflector antenna with the diameter of 3.7m is accomplished to prove the correctness and effectiveness of the model.(2) Basing on the coupled field model, a kind of feed adjusting method is presented to decrease the effect of the distorted reflector antenna on the electrical performances. The method determines the position and orientation of feed by the optimization model with the object of electrical performances in changeless structural design variables, and make up for the methods of feed adjusting when structure and electromagnetic are separate. Compared with the best-fitting parabolic method, this method is good for improving the electrical performances. These results could be referenced in engineering practice.(3) The electromechanical coupled field problem of planar slotted waveguide array antenna is studied, and an electromechanical coupled model of the antenna is acquired to relate the structural displacement field with the electromagnetic field. In the model, the structural displacement field includes the errors of the position and orientation of radiating slots. The errors of the slots voltages in the model are from the distorted slotted waveguide array and the process of manufacture and assembly of the antenna. These errors change the amplitude and phase distribute of radiating slots, a simple vectorial superposition is used to calculate far electric field of antenna. The coupled field model can be solved in the sequence way, the computational method of slots voltages is studies in detail. The deformation experiments of two prototype antennas with frequency bands of Ku and X are accomplished to certify the correctness and effectiveness of the model separately.(4) The effect of random vibration on the electrical performances in the air-bone antenna is addressed. Firstly, the displacement covariance matrix of the responded antenna structure from random vibration is calculated, the method of making the random samples of the distorted antenna is given according to the matrix, the electrical performances is obtained by the coupled field model of planar slotted waveguide antenna. Secondly, the weak regions are found by the responded distribution of the displacement and stress of the antenna and improved subsequently. Finally, numerical results indicate that the improved model decreases the effect of random vibration on the gain loss and pointing error, and can be referenced in engineering practice.(5) The effect of the deformation of antenna structure from the braze welding on the antenna electrical performances is carried out. Firstly, the deformation is analyzed by the finite element method and the technology of birth and death element, the effect of the physical properties of materials and temperature curves in the braze welding on the residual stress and deformation is obtained, the electrical performances are given by the coupled field model of planar slotted waveguide antenna. By analyzing the relations among temperature curves, the deformation and electrical performances, the temperature curve is improved to decrease the residual stress, the deformation and the influence on electrical performances. These results can be referenced in engineering practice.