Radiation properties of ring-shaped microstrip antenna array

In this paper, mutual coupling |S₂₁| between R-MSA (ring-shaped microstrip antenna) elements was estimated by the EMF method based on the cavity model. Then, the validity of the proposed method was tested by experiments. The experiments confirmed satisfactory agreement between the computed and experimental data for |S₂₁| in both E- and H-plane arrangements. In addition, a circularly polarized planar array composed of R-MSA elements was designed on the basis of the data of |S₂₁|. The experimental results of such a planar array demonstrated high performance in radiation pattern as well as axial ratio property. Furthermore, the active reflection coefficient |Γ| in the R-MSA array was also investigated in both equilateral and square arrangements. The computed results of active reflection coefficient in the array demonstrated high performance in both arrangements.