A compact TRM antenna with high impedance surface for SAR reduction at 1800Â MHz

In this paper, a compact tapered ring monopole (TRM) antenna with high impedance surface (HIS) is reported. This antenna is characterized by improved gain and reduced back lobe radiation. This provides specific absorption rate (SAR) reduction on human tissues, when used in a mobile phone. The reflection phase property of the HIS is used to increase the radiated field towards the antenna, thus providing a good return loss with 21% impedance bandwidth, 7.4 dBi gain and front to back ratio of 21 dB. In contrast to the already reported HIS ground planes, the proposed structure has a simple design methodology with compact form factor of 0.52λ × 0.52λ × 0.026λ at 1.8 GHz. The antenna prototype was fabricated and measurements were carried out. Further, numerical simulations were performed for SAR and thermal analysis. It is observed that SAR and consequent temperature rise in human tissues are greatly reduced, when HIS is added to the TRMA.