On Theories Of Coupled Multifield Problems And Methods Of Electromechanical Synthesis Analysis Of Antenna Structures

The electromechanical coupling problem has been an important bottleneck of many factors influencing the performances of military electronic fumishments, which have a typical multidisciplinary characteristic. Using the advantage and research achievements of Xidian University in antenna structural design, the dissertation discusses the coupled multifield problems (CMFP) involving the mechanical structural displacement field, electromagnetic (EM) field and temperature field, which mainly take place in design and analysis period of parabolic antenna and phased array antenna. The modeling theory and synthesis analysis method of CMFP are studied in detail.The least squared criterion based paraboloid fitting method is proposed. And the accurate calculation method for errors in axial, normal and radial direction of reflector surface is submitted. Based on the actual shape of distorted reflector and according to antenna mechanical structural analysis, a new divided-fitting method (DFM) is presented which is quite different from the traditional best-fit paraboloid method. It determines the boundary condition of each zone by first dividing the distorted reflector into many zones, then adopting Coons surface to fit each zone and combining the hoop function and radial function fitting methods. The boundary fitting functions include a trigonometric, polynomial and B spline functions etc. The reliability model of distorted surface precision and other two explored fitting methods are also introduced.Based on the analysis of distorted antenna structure, an accurate structural displacement field model of antenna is made. By the phase distribution of distorted antenna aperture, physical optics (PO) method and Fourier transform are used to calculation far electric field of antennas. Then an electromechanical coupling model of reflector antennas is developed. Aimed at the separated status of structural and EM design in antenna engineering, an integrated synthesis analysis system for large reflector antenna was developed by use of acquired electromechanical coupling model. The analysis platform testing has been made with two antenna engineering cases. Furthermore, based on the electromechanical coupling theory of reflector antennas, a mechatronic synthesis optimization design model is developed, which directly uses the electrical performance as the optimization object.A correlation factor consisting of focal length and diameter is introduced used in EM computation to develop a novel modified formula for antenna gainloss. And the corresponding mathematic expressions based on normal and radial error of reflector surface are presented respectively. By using the relationship among the transient wind pressure and speed and structural distortion, the mathematic expression of antenna gainloss under transient and average wind load is developed.To obtain an extremely high accurate surface precision and the EM performances, an electromechanical synthesis optimization analysis model of space antenna structures is developed, which adopts the axial gain of antenna and power consumption of actuators as the objective functions, the material strength of bars and actuator's mechanical capability and active travel of actuator as constraint conditions. Based on the synthesis optimization model, a new coupled structural-electromagnetic-thermal optimization model is also given. The applications of coupling optimization model demonstrate the potential for the significant improvement of performances and for less necessary effort for shape control of space antenna.The influence of position error of radiation element in rectangular planar active phased array antenna (APAA) on the electrical field intensity and directivity of antenna is studied. And the corresponding probability formula of field intensity is deduced. The characteristic of two basic deformations of APAA planar is analyzed. Then the mathematic model of thermal distortion error in planar of APAA is generated. Whereafter, the influence of rectangular planar distortion on the radiation pattern of APAA is studied. The analysis process of CMFP is also determined. According to the error model of antenna structural distortion, a coupled model involving displacement-electromagnetic-temperature field in rectangular planar APAA is established. The flow of coupled multifield analysis is drawn.