A compact antenna based on SRR and spiral with increased bandwidth and radiation efficiency

A compact planar microstrip antenna capable of providing tunable dual bands, broader bandwidths, and higher efficiencies is proposed. It is composed of a split ring resonator (SRR) etched on a topmost dielectric slab, together with a metallic spiral printed on a middle slab beneath and shorted via a pin to the metal ground plane. This pin drills through a bottom dielectric layer on which a feed line comprising a rectangular microstrip and a meander line for matching is printed. We seek to merge two resonances so as to expand the bandwidth (-10 dB), and increase the radiation efficiency. The designed antenna is of size 0.11λ_o along each side or 0.18 dielectric wavelength (ε_r = 2.2). The achieved efficiency is 55% at 1.7 GHz, and the bandwidth is more than double that of the single band counterpart.