A Heterogeneously Integrated 256-Element 5G Phased Array: Design, Assembly, Test

In this paper, we present the design, assembly, and test of a heterogeneously integrated dual-polarized 256-element 5G phased array covering 24$-$ 30 GHz. The design is based on a 64-element antenna-in-package tile designed using an organic substrate. This work represents one of the earliest examples of a heterogeneously integrated mmWave phased array module where each tile uses chips in three different substrate technologies to perform beamforming, frequency conversion, filtering, combining/splitting, and supply decoupling functions. The paper discusses the several challenges and system trade-offs for 5G mmWave phased arrays and illustrates the advantages of heterogeneous integration at the antenna-in-package level. The paper also covers, in detail, several practical aspects of phased array module design that are not well-described in existing literature, such as power domain modeling, module assembly, antenna feedline design, polarization isolation, and tile spacing. To demonstrate the efficacy of our design choices and techniques, we present exhaustive $\pm 360^\circ$ over-the-air beam characterization of the phased array antenna module demonstrating beam scanning over $\pm 70^\circ$ and very low cross-polarization leakage in E-/H-planes in both polarizations and in both TX and RX modes.