Some studies on microstrip square patch stacked antenna with 90° hybrid feed for dual band operation

The paper deals with the microstrip square patch stacked antenna (MSSA) with a 90° hybrid feed. Experimental investigations carried out on the antenna suggests that dual band operation is possible with this structure. The plot of the return loss shows two resonance frequencies with number of elements in the MSSA. The bandwidth is observed to increase with number of parasitic elements for both the resonance. In general the second resonance exhibits the larger bandwidth as compared to first one. In general, the resonance frequency of the two resonating modes depends on the inter element dielectric spacer thickness. There is a typical values of the dielectric spacer thickness for acrylic (0.02958 h), backelite (0.025905λ), glass epoxy (0.04695 λ) at which the two modes are resonant at a common frequency. The two modes become degenerate with a constant difference in resonant frequencies for the other values of spacing. Typically with paper dielectric spacer, two modes are found to be resonant at common frequency for three different values of dielectric thickness, viz. 0.0063885λ, 0.010649λ and 0.014908λ. The two modes become degenerate at dielectric thickness other than the specified values with a constant frequency difference of 0.377 GHz. It is further observed that the two resonating mode interchange the behavior after the common resonating point. The bandwidth at the common resonating point is found to be same