TCM-based miniaturization progress of a square microstrip patch antenna

A miniaturized square microstrip patch antenna (MPA) is analyzed and designed using the theory of characteristic mode (TCM). The TCM is applied to investigate and adjust the current distribution of the lowest resonance mode that the square patch can support. Based on the current distribution of the concerned mode, the two opposite edges of the patch where the characteristic current mainly concentrates on are curved with quadratic function curves. Then stubs are periodically loaded on the curved-edges, and the current along the curved-edges occurs slight changes. At last, two apertures are etched on the patch, and more current trends to flow along the edges of the apertures. The above three approaches are examined through TCM, and all lead to reduction of resonance frequency of concerned mode. After optimizing the position of the probe-fed, a 60% miniaturization in the size of the square MPA is achieved. The TCM is expected to provide more effective guidance in antenna miniaturization design.