A broadband electromagnetically coupled patch antenna with robust characteristics against layer misalignments

Traditional two-layer electromagnetically coupled patch (EMCP) antennas use dielectric materials with low dielectric constants as substrates for both the driven and parasitic patch with either air or foam is used as the layer separation. This paper presents a broadband and high gain EMCP antenna that uses a high dielectric constant (ε_r = 6.15) material as the substrate and a low dielectric constant (ε_r = 2.2) material as the superstrate. The proposed EMCP element is microstrip-line fed and operated at X-band with a centre frequency of 10 GHz. The aim of this study is to examine the immunity of the proposed EMCP element against the layer misalignments, which include both the angular and linear displacements of the top-layer. Contrary to the results from the conventional EMCP antennas, which are very sensitive to the layer misalignments, our results showed different impedance behaviour that is very robust against both the angular and linear displacements. We also set the 10% impedance bandwidth (VSWR<2) as the criteria to locate the limits for all displacements in x-y plane.