Total Array Gains of Polarized Millimeter-Wave Mobile Phone Antennas

This paper studies a gain of an antenna array implemented on a mobile device operating at a millimeter-wave radio frequency. Assuming that mobile phones at millimeterwave range operate with a single transceiver chain and analog beamforming like phased arrays, its total array gain is attributed to average gains of antenna elements and signal precoding or combining gains in excess to received power from a single-element dual-polarized omni-directional antenna. The total array gain circumvents the ambiguity of conventional array gain which cannot be uniquely defined as there are multiple choices of a reference single-element antenna in an array. Different polarized 8-element patch antenna arrays implemented on a mobile phone chassis, i.e., uniform linear array (ULA) and distributed array (DA) operating at 60 GHz, are studied. The antenna elements are placed so that they cover vertical, slanted or horizontal polarizations. The gain is evaluated for different orientations of the chassis along with effects of a body torso and a finger of a person operating the phone. The gain in a small-cell scenario shows that DA achieves higher gains than ULA regardless of polarization states of antenna elements at the base and mobile stations, and of the existence of line-of-sight in the links. Antenna polarizations do not make much impact on the total array gain as random orientation of a mobile phone and finger shadowing modifies the polarization states. The results show that antenna array geometry is more influential design aspect than polarization when a single transceiver chain is considered.