An Optically Invisible Antenna-on-Display Concept for Millimeter-Wave 5G Cellular Devices

This paper proposes the novel concept of an optically invisible antenna built using photolithography that can be integrated in active display panels such as organic light emitting diodes and liquid crystal displays. Represented as antenna-on-display (AoD), this proposed approach is exemplified for future millimeter-wave (mmWave) 5G cellular devices. Empirical examinations confirm that the devised diamond-grid-shaped 2000 A-thick Ag-alloy electrodes on a glass substrate feature electrical loss characteristics of approximately 0.4 dB/mm at 28 GHz amid 88% optical transparency. Using the aforementioned material, a transparent diamond-grid antenna element is formulated and verified. Complete optical invisibility is achieved by implementing identical dummy grids around the antenna region. A multilayer schematic is designed in order to expand the antenna element into a phased-array configuration. The designed and fabricated 1 x 8 optically invisible AoD exhibits 6.66 dBi boresight gain at 28 GHz while maintaining 88% optical transparency. This gain includes 1.5 dB feedline loss and approximately 4 dB anisotropic conductive film (ACF) bonding loss. Current challenges include the immaturity of the ACF bonding process and the gain degradation caused by the dummy grids, and these need to be addressed to further improve the presented AoD concept. Nonetheless, this paper aims to serve as a foremost example for future optically invisible AoD.