Transformation optics, which is based on the form invariance of Maxwell equations under different coordinate sets, has become a powerful tool to manipulate the propagation path of electromagnetic waves. The development of metamaterials also facilitates the practical realization of transformation- optics-based devices. In this paper, we propose a general transformation to design a horn antenna with high directivity by using homogeneous and ani-sotropic media. As long as the horn antenna is divided into several triangle blocks and the general transformation is applied, the material property in each block is homogeneous. Full-wave simulation based on the finite element method is performed to indicate the performance of the device. According to the numerical results, it is found that the electromagnetic field inside the horn area can be either stretched or compressed at will, and simultaneously fields outside the device are little disturbed. Thus, it offers us considerable freedom in designing the high-gain antenna. Furthermore, it is also demonstrated that the radiation direction can be arbitrarily controlled by carefully setting the geometrical parameters of the antenna. In the end, a multiradiation beam antenna, as one of the potential applications, is investigated.
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