This paper proposes a dual-band metasurface to enhance the transmission through the phone glass covers of millimeter-wave array modules. This is done without adding extra substrates between the glass cover and the array module. In this case, the metasurface is printed on both faces of the glass cover. The total 3-dB bandwidth is 6.68 GHz, shared between the two bands. The proposed metasurface has been tested with a patch array antenna, but the solution is universal for broadside radiating arrays.
Rodriguez-Cano et al. (Mon,) studied this question.