LTCC-Based Antenna-in-Package Array for 5G User Equipment With Dual-Polarized Endfire Radiations at Millimeter-Wave Frequencies

An antenna-in-package (AiP) of endfire and dual-polarization at 28 GHz is presented. It is formed by four periodic antennas of broad bandwidth and high-isolation, fabricated by the low-temperature cofired ceramics technology. The dual-polarizations are realized by integrating a horizontal metal stripline-coupled dipole with a vertical magneto-electric monopole, incorporated into a multilayer architecture for compactness. The AiP skillfully implements vertical vias and horizontal strip lines in the cavities between antennas to improve isolation and polarization purity. This AiP has numerically been examined for endfire high gain and beam steering in user equipment (UE) applications. The prototype was measured to show good isolation lower than −25 dB from 26.5 to 29.5 GHz and agree with full-wave simulations. The antenna array is finally integrated with 1 \times 4 boresight radiation microstrip antennas to form a complete UE AiP.