Total array gains of millimeter-wave antennas on a mobile phone under practical conditions

This paper studies a gain of an antenna array implemented on a mobile device operating at a millimeter-wave (mm-wave) radio frequency. Assuming that mobile phones at mm-wave range operate with a single baseband unit and analog beamforming like phased arrays, its total array gain comes from signal precoding or combining in excess to the omni-directional pathloss. 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. Two types of 8-element patch antenna arrays implemented on a mobile phone chassis, i.e., uniform linear array (ULA) and distributed array (DA) both operating at 60GHz, are studied. The gain is evaluated in a small-cell scenario in an airport shows that the DA achieves higher median gain by up to 8dB than the ULA when different orientations of the mobile phone are considered along with a body torso and a finger of a person operating the phone. There are always postures of the mobile phone where the ULA cannot see the line-of-sight due to directionality of the patch antenna on the mobile phone chassis and of body and finger shadowing, leading to outage array gain of -15dB. The DA has much smaller variation of the gain across different orientations of the phone, even when the human torso shadowing and user's finger effects are considered.