Platform Characteristic-Mode-Based Omnidirectional Antenna Design Using Convex Optimization

This communication focuses on the rapid synthesis of platform antennas with specified polarization and beam shapes using a small number of significant modes and a limited number of exciters. Following the theory of characteristic modes (CMs), the CM-based radiation pattern synthesis problem is transformed into a convex optimization problem to constrain modal weighting coefficients (MWCs) and achieve a near-optimal sparse excitation voltage vector. The excited radiation patterns could be predicted from the weighted CMs. The distribution of near-optimal sparse excitation voltage vector provides quantitative information for exciter locations. Furthermore, in the second convex optimization problem, the influence of port coupling among the excitation ports and the input impedance property of each exciter is further considered by the embedded pattern synthesis method. The location, excitation amplitude, and phase of the exciters are quantitatively solved from the two convex optimization problems. A vertically polarized omnidirectional antenna on a simplified 3-D aircraft model is taken as an example to verify the proposed method. Both the measured and simulated results demonstrate the effectiveness of the proposed method in achieving radiation performance and sparse excitation distributions over a platform.