High Head–Hand Efficiency and Low-SAR Mobile Phone Antenna Design Based on Unidirectional and Uniform Current Distribution
Meng Liang, Di Yu, Huan Huan Zhang, Nan Wang, Ying Liu, Chao Zheng, Yun Feng Dong, Yong Jian Han
Abstract
A high head-hand efficiency and low-SAR mobile phone antenna is proposed in this article. The impact of the antenna’s current distribution on its efficiency and spatial-average specific absorption rate (SAR) is analyzed, revealing that unidirectional and uniform current distributions on the antenna can achieve a dual benefit of high head-hand efficiency and low-SAR values. Based on this idea, a double loop antenna consisted of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\lambda $ </tex-math></inline-formula> outer loop with differential feed and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5\lambda $ </tex-math></inline-formula> inner loop with coupled feed is designed, which can implement unidirectional and uniform current distribution in a wide frequency band. The measured −6 dB impedance bandwidth of the proposed antenna can cover 1710–2690 MHz. Its measured average head-hand efficiency from 1710 to 2690 MHz is −5.3 dB (29.5%). Its simulated normalized peak head and body SAR values are lower than 1.0 W/kg.