A Low-Profile Dual-Band Dual-Polarized Quasi-Endfire Phased Array for mmWave 5G Smartphones
Menglou Rao, Kamal Sarabandi
Abstract
This paper presents a very low-profile ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.105\lambda _{0}$ </tex-math></inline-formula> at 28 GHz) dual-band dual-polarized millimeter-wave phased array for 5G smartphones. The array element is based on two distinct dual-band antennas to realize two orthogonal linear polarizations. A planar folded dipole with a parasitic strip is used to produce horizontally polarized radiation, and a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">hexagonal bridge antenna</i> is devised to generate vertically polarized radiation while maintaining a very low profile. A prototype of 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> phased array is designed and implemented on a multilayer laminate using standard printed circuit board process. The real estate of the array is kept within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.5\,\, \mathrm {mm}\times 23\,\, \mathrm {mm}\times 1.12\,\, \mathrm {mm}$ </tex-math></inline-formula> . For both polarizations, the −10 dB bandwidth covers 25.4–30.84 GHz and 38–40 GHz with peak gains of 11.31 and 11.93 dBi at two center frequencies, respectively. The overlapped 3 dB scan ranges between both polarizations are ±45° at 28 GHz and ±39° at 39 GHz. This work considers a number of important design challenges of implementing low-cost mmWave antennas in smartphones, providing a practical solution to mmWave 5G mobile devices.