An electrostatic forming membrane reflector with AstroMesh structural support is a new concept for space-borne deployable antennas. A membrane shape-control optimization model is proposed in this study for electrode design to achieve high reflector precision. In this model, the electrode number, channel number, and voltages are considered design variables, the membrane reflector precision is an objective function, and the positivity and uniformity of membrane stress are constraints. A technology that combines a gradient method and genetic algorithm is proposed to solve the optimization model. This technology includes continuous and discrete design variables with different values and dimensions. The validity and effectiveness of the optimization model are demonstrated via the numerical example of a 5 m membrane reflector and a 0.55 m experimental prototype.
A new method is proposed for the antenna aperture illumination design on microwave wireless power transmission. Bezier curves are used to describe the aperture amplitude distributions. By optimizing the coordinates of the associated Bezier points, an aperture distribution yielding the maximum beam collection efficiency (BCE) can be achieved. Moreover, edge tapers can be easily controlled by the Bezier curves. The proposed method shows its effectiveness from carrying out extensive numerical experiments on different Fresnel parameters as well as edge taper constraints. The results show that larger aperture power coefficients obtain with a little sacrifice of BCEs when larger edge taper constraints are considered. Besides, the peak lobe irradiated outside the rectenna can be suppressed as well.
Mechanical distortion errors in active phased-array antennas (APAA) include both random error and mechanical distortion. Random error is generated during the manufacturing and assembly process, and mechanical distortion is caused by external loads such as high thermal difference, vibration and impact loads. The combination of random error and mechanical distortion results in unexpected and significant degradation of the antenna electromagnetic performance, which has become an obstacle to development of high-performance APAA. After introducing the mechanical distortion errors into the antenna electric field as an additional phase factor, a coupled structural-electromagnetic model of the planar rectangular APAA was developed to describe the coupling relationship between mechanical distortion error and electromagnetic performance. The combined influences of the radiated element numbers, mechanical distortion and element position random error on the antenna electromagnetic performances are analysed, and valuable results for engineering application are discussed.
This paper provides a survey of research activities of Large spaceborne deployable antennas (LSDAs) in the past, present and future. Firstly, three main kinds of spaceborne antennas, such as solid reflector, inflatable reflector and mesh reflector, are issued by showing the strengths and weaknesses. Secondly, a detailed research situation of LSDAs with mesh is discussed, for majority of the in-orbit large diameter and high frequency antennas are made in this type of structures. Thirdly, new conception of antenna is proposed as it does have both advantages of large aperture (high gain) and high precision (high frequency). Fourthly, the design theory and approach of LSDAs are concerned. It includes thermal-electromechanical multidisciplinary optimization, shaped beam design technique, performance testing technology and evaluation method, passive intermodulation of mesh, and application of new materials. Finally, the ultra large spaceborne deployable antennas of the next generation are presented, such as the deployable frame and inflatable reflector antennas, space-assembled ultra large antennas, smart array antennas and so on.
The presence of a metal space frame (MSF) radome inevitably degrades the electromagnetic (EM) performance of the enclosed antenna, while the deformation of the radome can worsen the degradations. In this study, with the introduction of the concept of variable size member, a multidisciplinary optimisation model is proposed to implement the sizing optimisation for the members of MSF radomes to improve simultaneously the EM performance, structural performance, and self-weight simultaneously where EM analysis and structural analysis are involved. Furthermore, a method is presented to boost the efficiency of the EM performance analysis, which makes possible the optimisation of electrically large MSF radomes. A 70m MSF radome is simulated, and the results indicate that the proposed radome design with variable size members is superior to the conventional radome design with constant size members in terms of all the optimisation objectives, especially the EM performance and self-weight. Several conclusions with guidance values are drawn based on the results.
At the stage of structural optimization, the subreflector structure should be designed such that it compensates for the residual error or relaxes the accuracy requirement of the main reflector to a certain extent. However, there is no fast and effective means to shape the subreflector during the structural optimization process. This communication is based on the application of geometrical optics (GO)/physical optics (PO) analysis to shape a subreflector for antenna distortion compensation. Thus, a method performing an iterative approximation to the GO/PO analysis is proposed. Unlike GO shaping or optimization, the proposed method is not formulated by simultaneous nonlinear ordinary differential equations. Therefore, the main contribution of this communication is that the method does not entail computationally intensive calculation and optimization, and thus, it does not require a large amount of time to complete the calculation. The proposed method is very suitable for a large reflector antenna with a small-amplitude deformation and smoothly varying errors such that the shaped subreflector does not have a significant effect on the amplitude of the main reflector's electric field. An example with regard to the symmetric system is presented. The obtained results demonstrate that the proposed method is effective.
This paper proposes an efficient method for analyzing the radiation, scattering, and port properties of finite antenna arrays based on the theory of characteristic modes. Using the characteristic modes of isolated radiating elements, we obtain the electrical properties of a finite antenna array, which is different from the traditional modal analysis method for the entire array. The modal excitation coefficients of radiating elements in an array environment are derived by considering the mutual coupling effect that is characterized from the perspective of modal coupling between different elements. The characteristic modes of isolated radiating elements are analyzed using the method of moments. The proposed method can handle the array problems with arbitrary spacing between elements and arbitrary excitation distributions. Since the characteristic currents are used as higher order basis functions and the periodicity of the arrays is considered, the computational efficiency could be significantly improved. Numerical experiments are provided to demonstrate the proposed method.