Reconfigurable beam steering using U-slot patch antenna with high gain and low SAR for wireless headset applications

This article presents a reconfigurable beam-steering patch antenna with high gain and a low specific absorption rate (SAR) for wireless headset applications. The proposed antenna was designed as a U-slot patch antenna, which was fabricated on an FR-4 substrate. The antenna was designed to steer the beam directions at the operation frequency of the bluetooth band (2.4-2.48 GHz). To implement the beam steering capability, the antenna used two PIN diodes. Through the use of PIN diodes, the antenna presented three beam directions (state 0, 1, and 2). The measured peak gains of the antenna in the headset were 4.22-5.15 dBi and the overall half power beam width was 102°. The measured total radiated powers of the three states (state 0, 1, and 2) were 21.94, 20.66, and 20.61 dBm. The measured total isotropic sensitivities of the three states were -92.0, -90.0, and -91.0 dBm. In addition, the measured SAR values of the antenna on the body were less than 0.149 W/kg in all states, satisfying the SAR criteria of the USA and the EU.