| Active phased array antennas(APAA)have been widely applied in strategic missile warning,airborne fire control,satellite imaging and many other fields because they offer advantages such as high reliability,multi-function,good stealth performance and other unparalleled advantages.With the development of word military technology,the trend of APAA towards to high density,high gain,low side lobe and so on.As a result,the coupled structural-electromagnetic-thermal(SET)problem severely restricts the realization of high performance APAA.Therefore,this thesis is mainly concerned with the coupled SET modelling,structural error influence mechanism and SET integration optimization design method.The author's major contribution can be summarized as follows.(1)The key to research the coupled SET problem of APAA is to establish the coupled SET model.But in the existing research,the preliminary coupled SET model including load and thermal deformation is established.Therefore,the deviations of space phase difference and mutual coupling caused by element position errors are analyzed.Meanwhile,the change of the pattern in the array is studied by considering the element deflection.The influence of temperature on the device performance is analyzed.On this basis,the coupled SET model including element position offset and deflection,mutual coupling and pattern distortion in the array and device performance temperature drift is developed.In addition,the coupled structural-electromagnetic statistical model of the planar rectangular grid APAA is deduced.The establishment of the coupled SET model laid a theoretical foundation for the influence mechanism study of error and design of SET integration.(2)The experimental model design and processing of APAA are completed,and the correctness of the coupled SET model is verified.Firstly,the Quasi-Yagi antenna,power splitter,cold plate,T/R analog heat source are designed and processed,and formed a 1×8 linear array.Different position errors are obtained through the artificial adjustment of the element position,and then test the changes of antenna performance under the different element position errors.At the same time,the changes of the line array antenna performance under the same element position errors are calculated by using the coupled SET model and the commercial software,and the correctness of the coupled SET model is verified by comparing with the results of testing.In addition,the T/R shell temperature is tested by using liquid cooling method.Then,the mechanism of the T/R module temperature drift on the performance of antenna is studied by using the coupled SET model.The results show that the T/R module shell temperature should be less than 70 ? and the maximum temperature difference should be less than 10 ?.(3)The random errors of the elements result in deterioration of the antenna performance,especially the sidelobe level.In the existing research,the influence of the element position error is equivalent to the influence of the excitation current amplitude and phase error.Then,the influence of amplitude and phase error on the antenna average electrical performance is analyzed by using probabilistic statistical method.However,the element position error as a structural tolerance,its influence on the antenna performance cannot be simply measured by the influence of the excitation current amplitude and phase error.Therefore,the influence mechanism of element position installation error on antenna performance is studied from the perspective of SET coupling.Firstly,the element position random error is subdivided into the element installation accuracy and installation flatness.Then,the influences of the element position random error on performance of rectangular grid array and triangular grid array under different plane sizes are analyzed,and the relevant data and curves are obtained,which can provide the corresponding guidance for the structural design of APAA.(4)One of the critical issues in the design of APAA structure is to determine the installation tolerances of array elements.It is common to set one installation tolerance for all elements,but this increases manufacturing difficulty and cost.Thus,a method of determining the element installation tolerance considering the element position influence is proposed.Firstly,the initial interval of the element installation tolerance is specified.Then,the sensitivity information of antenna performance for element position error is obtained by find the partial derivatives of the array factor with respect to element positon.Thereby,the change rate of the tolerance interval for each element is determined based on the sensitivity information.After that,thousands of element position random error samples are generated in the tolerance interval of the element position,and then calculate the performance of the antenna by using the coupled SET model.When the error samples which get the electrical properties to meet the requirements reach 95%,the current threshold is the element position tolerance.The case analysis results show that the proposed method is feasible and effective.(5)The working environment of APAA is very complicated,such as vibration,heat power and so on will cause the plane deformation.Meanwhile,there are random errors in the array element position.These two kinds of errors exist at the same time and the nature is different.But in existing research,the impacts of two types of errors are analyzed separately.Therefore,the comprehensive mechanism of the plane structural deformation in the service environment and element position random error on performance of antenna is studied based on the coupled model.When the statistical impact of random error is not considered,the relationships between the plane deformation,element position random error,array plane size and the electrical performance of the rectangular grid APAA are analyzed.Meanwhile,the conditions of whether to need to consider the statistical impact of random error are discussed by comparing with the calculation results of the coupled structural-electromagnetic statistical model of the rectangular grid APAA.Finally,the electromechanical coupling performance calculation software of APAA is developed.(6)The traditional design method of APAA is structural,electromagnetic and thermal separation design,which leads to the high product repetition rate,long development cycle,too harsh single subject index and so on.Therefore,the SET integration optimization design method of airborne APAA is studied based on the coupled SET model.The SET integration optimization model is established with the antenna gain and weight as the goals,the inlet flow rate of the coolant and the section size of the cold plate flow channel are optimized.The optimization process covers structural parametric modeling,thermal analysis,thermal-structural grid matching,structural deformation analysis,and antenna performance calculations by the coupled SET model.The experimental results show that the SET integration optimization design method can guarantee the electrical performance of APAA and get the best thermal and structural design scheme,effectively reduce the antenna weight. |
PDF Full Text Request