Package-Integrated, Wideband Power Dividing Networks and Antenna Arrays for 28-GHz 5G New Radio Bands

Abstract

Package-integrated and ultrathin power dividers with footprint smaller than unit $\lambda ~_{0}~^{\mathrm{ 2}}$ at the operating frequency of 28-GHz 5G new radio (NR) n257 and n258 bands are presented for the first time for small-cell applications. These power dividers are also configured as antenna arrays using endfire Yagi–Uda antenna elements. Utilizing minimal matching techniques, two-, three-, and four-element antenna arrays are designed without compromising on the bandwidth of operation or electrical performance. These thin-film power dividers exhibit a cross-sectional height of $147~\mu \text{m}$ and can be implemented in the top metal layer of front-end module packages. Panel-compatible semiadditive patterning (SAP) process is utilized to realize these structures, which yields precise line space dimensions required for millimeter-wave (mm-wave) applications. This results in power dividers with low added insertion loss, low VSWR, and minimal phase difference between output ports. The added insertion loss is 25% less than similar structures reported on integrated fan-out architectures. The antenna arrays exhibit high gain and efficiency. Excellent model-to-hardware correlation is observed with multiple coupons of the same structure. Package-integrated power dividers and antenna arrays based on ultrathin laminated glass substrate represent a major step toward realizing compact mm-wave antenna-in-package for 5G small-cell applications.