SAR reduction using a single SRR superstrate for a dual-band antenna.

A dual-band microstrip antenna operating at GSM 900 and GSM 1800 MHz is designed initially. Then a single split ring resonator (SRR) structure is used as a superstrate for this dual-band antenna. A circular current is induced in the SRR due to the perpendicular plane wave excitation, which in turn leads to an electric excitation coupled to the magnetic resonance. It also exhibits higher order excitations at 0.9 and 1.8 GHz which ultimately resulted in specific absorption rate (SAR) reduction of human head at both the designed frequencies of the antenna. The antenna and the SRR superstrate are printed on a 1.6 mm thick FR-4 substrate of dimension 59.6 × 49.6 mm. Analysis of the SRR using the classic waveguide theory approach is discussed. Radiation pattern of the antenna in the presence of SRR superstrate and human head is also discussed. Prototype of the antenna along with the SRR superstrate is fabricated and measured for return loss and radiation pattern. Measurement results fairly agree with the simulated results. A human head phantom is utilized in the calculation of SAR.