A switched beam HSRR-like antenna for on/off-body communication

This paper presents a dual-band electrically small antenna consisting of a one half of a split ring resonator (HSRR-like) which is located on a square ground. The antenna design allows the radiation pattern to switch between two orthogonal directions with respect to the ground plane depending on the frequency of the excitation signal at 950 MHz (lower resonance) and 2.25 GHz (upper resonance). The matching of the antenna to a 50-Ω line is reasonably acceptable where the measured reflection coefficients are better than -13 dB at both resonance frequencies. The simulated efficiency of the antenna at the lower and upper resonance frequencies are approximately 80% and 95%, respectively. Additionally, an estimation of the antenna gain (realized) obtained from simulation shows -0.5 and 1.2 dB, respectively for the lower and upper resonance, which are acceptable for a small antenna. The robustness of the radiation characteristics of the antenna is also investigated while situating the antenna on different parts of a volunteer´s body when the reflection coefficients are measured over a frequency band ranging from 1 to 4 GHz.