Radome Wideband Slab Design And EM Analysis Compsation

In order to ensure the normal operation of an antenna in its terrible environment, a radome is widely employed in the field of EM transmitter and receiver. Because of the resonation property of microwave, the radome impacts on radiation performances of antenna severely. The radome effects include: introduction of an insertion loss, increased antenna sidelobe levels, introduction of a boresight error and so on. The design techniques of radome are closely related to many subjects such as: materials, electromagnetics, mechanics, thermology etc. For instance, because of air friction force of high speed missile, it induces high temperature. Material properties change with temperature. In the end, the radome performance will be change. In this thesis, the main contents are summarized as follows:Effective permittivity analysis methods of porous material are studied. The analysis of effective permittivity is meaningful for the design of porous material and composite material and it is the basis of design graded material plate. The traditional effective permittivity analysis theories are difficult to analyze the structural effect. The free space method combined with numerical simulation is applied to analysis the equivalence dielectric constant of material. The dispersive and temperature effects of material are taken into consideration. The accuracy of the method is evaluated by simulation. The effective permittivity of arbitrary porosity and arbitrary frequency can be solved by using curve fitting method.Optimization design methods of broadband transparent graded material slab are studied in this thesis. Compared with narrow band devices, broadband wireless equipments have more advantages and brighter prospect. So the research on wideband radome design is meaningful. In comparison, the graded material slab is a good choice to realize wideband radome. Two design methods are presented to design wideband gradient dielectric slab. Firstly, a traditional analytic design method is proposed. A gradient honeycomb structure is applied to realize wideband transparent slab. The high pass property is verified by finite element method simulation. Moreover, a hybrid optimization method combined trust region method and genetic approach is presented to design wideband gradient material slab in this thesis. Relatively, this method has better global property and better convergence speed; Secondly, the dynamic range of dielectric constant is taken into account so as to avoid the disadvantage of poor mechanical performance under the condition of low dielectric constant distribution. Thirdly, the temperature effect on material permitivity is taken into accounted during the optimization process because the temperature range of the hypersonic radome is relatively large.A hybrid method combining full wave simulation software and the near field aperture integration method is presented to analysize the radiation of radome-enclosed waveguide slot array. Firstly, the field distribution data of each slot, which is simulated by full wave simulation software, is exported. Then the export data is applied as excitation in aperture integration algorithm to analysis radome. By this way, the mutual coupling effects of each array element are taken into accounted and it is more accuracy than tranditional methods that utilize ideal amplitude and phase distribution.The distoration compensation methods of radiation pattern which is induced by phased control array radome are studied in this thesis. Compared with mechanical scanning antenna array, the distoration compensation methods of the phased array radome have more choices. The synthesis of radome-enclosed antenna array excitation can relieve pattern degradation induced by radome. When the radome effect is taken into consideration the excitation synthesis method is different from the traditional synthesis of planar array. Because the relative position is different between the element and radome, each element pattern is different. The radome-enclosed element patterns are obtained by using physics optics method in references. In this thesis, the element patterns of radome effect are analyzed by full wave simulation software. The advantages of this approach are: it can handle the element model with complex structure; the element pattern is more accurate; the coupling of each element is considered. The validity of synhesis resluts are evaluated by full wave simulation.In addition, an efficient conformal array optimization method is proposed by using near field aperture integration method. The conformal array surface is equivalent to a virtual air radome. By using the equivalent planar array, the initial polarizations, magnitudes and phases are solved by the projection from planar array to conformal surface. Then, the trust region method is applied to approximate the objective pattern. During the optimization process, the cross polarization and the dynamic range ratio of excitation are taken into acount. By comparing with references, the proposed method saves the computing time of optimization obviously, because it is based on reasonable initialization, analytical gradient and Hessian Matrix.