A Cost-Effective Antenna-in-Package Design With a 4 x 4 Dual-Polarized High Isolation Patch Array for 5G mmWave Applications

A cost-effective antenna-in-package design based on a 4 x 4 dual-polarized high isolation patch array for 5G mmWave applications is proposed in this paper. To obtain a cost-effective design, we devised a four-layer metal stack-up structure with dielectric materials consisting of one TLY-5 polytetrafluoroethylene (PTFE) and two FR-4 epoxies. The devised stack-up exhibits a simple and compact geometry due to the small number of layers, which allows the design to be manufactured using a low-priced standard printed-circuit-board process. Additionally, the employed material combination in the stack-up design possesses a high-end PTFE only in the region with the antenna radiators, which enables good antenna radiation performance at an affordable price. In addition, to design a high-isolation patch array for dual-polarized applications using the low-layer stack-up structure, we employed capacitive probes, defected ground structures, and the rotated-fed method in the proposed array design. With these techniques, the designed array exhibited excellent performance with respect to both port-to-port isolation and cross-polarization isolation. The mechanism of improvement in port-to-port isolation was clearly described using the established equivalent circuit model of the proposed structure. As a result, the fabricated antenna-in-package has the reflection coefficients of less than dB in the targeted frequency range of 26.5-29.5 GHz and has a peak gain of 17.37 dBi at 28 GHz. The measured port-to-port isolations and cross-polarization isolations are higher than 22.63 and 30 dB in the targeted frequency band, respectively.