Smartphone Antenna on Display (AoD) Design at Millimeter-Wave Frequencies With Enhanced Transparency and Ground Plane

Antenna on display (AoD) for user equipment (UE) is attractive but faces challenges in implementation. Key factors impacting the AoD implementation are examined in this article. To illustrate the basic behaviors and demonstrate its feasibility, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 4$ </tex-math></inline-formula> optically invisible antenna array is designed, fabricated, and implemented on a display panel at a 5G millimeter-wave (mm-wave) frequency band of 28 GHz. Metal mesh is used as a conductor in the antenna design to provide a high transmittance of around 88%. Novel dummy metal grids of electromagnetic (EM) transparency are added around antennas to increase the optical invisibility of AoD. Moreover, an mm-wave beamforming board and a feeding network on a flexible printed circuit (FPC) board are implemented to emulate the actual scenario for the AoD design. The maximum antenna gain of 7.36 dBi for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 4$ </tex-math></inline-formula> optically invisible antenna array has been achieved with the scanning range between ±30°.