Highly Compact Integrated Sub-6 GHz and Millimeter-Wave Band Antenna Array for 5G Smartphone Communications

In this article, a dual-band integrated compact phased-antenna array is proposed for fifth-generation (5G) smartphone communication. The proposed single-layered substrate-based antenna array has a dual band, wideband, high gain, and wide beam-steering function. The dual bands were achieved by passive integration of meandered lines and a microstrip patch antenna using a dual-stub-based filter. Owing to the small size of the antenna array (56.65 mm <inline-formula> <tex-math notation="LaTeX">$\times4.95$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation="LaTeX">$\times0.508$ </tex-math></inline-formula> mm), it was installed on both the top and side metal frames of a smartphone in a vertical position, allowing a wide beam coverage with a high gain. The proposed antenna provided the −6 dB bandwidths of 250 and 3520 MHz at 3.5 and 28 GHz, and the −10 dB bandwidths of 110 and 1890 MHz were observed at 3.5 and 28 GHz, respectively. The radiation performance with a smartphone model and a hand phantom were analyzed in detail. Furthermore, a safety study on the power density (PD) and specific absorption rate (SAR) of the arrays with frequency-dependent hand and head models was conducted. Finally, we fabricated an antenna array prototype, and compared the measured results with the simulation results, which showed a good agreement.