LTCC-Based Dual-Polarized AiP Module by Multilayered Cross-Dipole Antennas for 5G Mobile Terminal Applications at 28 GHz Band

An antenna-in-package (AiP) of
$4\,\, {}\times {}4$
elements with dual-polarized radiations for high-power radiation at a 28 GHz band was designed and fabricated by low-temperature co-fired ceramic (LTCC) for fifth-generation (5G) applications. The design starts with selecting cross-dipole elements to ensure good polarization purity. The l/4 separation from a ground plane is achieved by considering a proper combination of multilayered substrates’ thicknesses and their dielectric constant, where the feedings are probed by coaxial-type vias from the bottom. The dipole arms’ shapes are optimally tuned to achieve broadband reflection coefficients. This AiP has the advantage of dual-polarizations along +/−45° to avoid harmful interferences from metal-supporting structures, reasonable inter port isolations, and low cross-polarization levels (XPLs). The AiP has a compact profile of
$28\,\, {}\times {}28$
mm2. The interport isolation between the polarization excitation ports is larger than 33 dB from HFSS full-wave simulations. The elements’ bandwidth is larger than 6 GHz from the full-wave simulation and broader than 4 GHz from measurements over the antenna prototype. The array has a bandwidth larger than 6 GHz from measurement with a maximum gain of 16.6 dBi and a sidelobe level (SLL) of 13.3 dB, validating the design concept.