A SAR Reduced mm-Wave Beam-Steerable Array Antenna With Dual-Mode Operation for Fully Metal-Covered 5G Cellular Handsets

TLDR

The authors propose a 28 GHz beam‑steerable antenna array with dual‑mode operation that reduces specific absorption rate (SAR) for fully metal‑covered 5G handsets. The design uses two eight‑element rotated slot subarrays mounted on the handset’s upper frame and back cover, with a switch selecting the subarray for each mode. Measured results show reflection coefficients from 27.2 to 28.2 GHz, inter‑element coupling below –11.8 dB, hemispherical beam coverage, and peak SAR values of 0.53 W/kg at 0° and 0.88 W/kg at 40° with 24 dBm per subarray.

Abstract

In this letter, a specific absorption rate (SAR) reduced 28 GHz beam-steering array antenna with dual-mode operation for a fully metal-covered fifth-generation (5G) cellular handset is proposed. The proposed antenna consists of two subarrays, each of which has eight rotated slot antenna elements, which are arranged on the upper frame and on the part of the back cover of the handset. The subarrays are selected according to the modes by using a switch. The proposed array demonstrates good reflection coefficients in the frequency band ranging from 27.2 to 28.2 GHz and the mutual couplings between antenna elements are less than -11.8 dB. The proposed antenna has good beam-steering properties and a hemispherical beam coverage for a millimeter-wave (mm-wave) 5G cellular handset. The calculated peak SAR values on the head phantom by the proposed structure, for the beam scan angles of 0° and 40°, are 0.53 and 0.88 W/kg, respectively, when the input power of each subarray is 24 dBm.