Efficient Characteristic Mode Analysis for Radiation Problems of Antenna Arrays

The analysis for large-scale antenna arrays is a hot topic for design and optimization. In this paper, an efficient method for analyzing antenna arrays by using characteristic mode (CM) is proposed. In order to analyze common antennas composing of conductor and dielectric, the theory of CM is first introduced into the volume-surface integral equation. An auxiliary general eigen-equation is established to make the modes orthogonal. Furthermore, a source mode (SM) is constructed to modify the accuracy when using CMs to expand the currents excited by a delta gap source for antenna problems. To demonstrate the influence of antenna structures and excitations on the CM and SM, three antennas are analyzed and only a few modes are required to achieve a good accuracy. Due to the periodicity of antenna arrays, CMs can be served as entire-domain basis functions defined on one antenna element and reused to reduce the unknowns in the method of moments (MoM). Numerical results have shown that the proposed method can have a good agreement with the traditional MoM. Meanwhile, both the memory requirements and computational time of the proposed method can be significantly reduced.