Broadband and Wide-Angle Scanning Capability in Low-Coupled mm-Wave Phased-Arrays Incorporating ILA with HIS Fabricated on FR-4 PCB

This paper presents a compact millimeter-wave (mm-Wave) phased array incorporating inverted-L antenna (ILA) with high-impedance electromagnetic surfaces (HIS) based on single-layer FR-4 PCB for user equipment (UE). In order to realize mm-Wave UE in low production cost, the design methodology of phased array antenna in single-layer FR-4 PCB is proposed without any additional packaging process. The presented antenna consists of low-coupled antenna element and low loss feeding networks in compressed linear array configuration with 0.39λ0 inter-element spacing. First, in order to realize broadband characteristics, the ILA is integrated with one-dimensional electromagnetic bandgap (1-D EBG) structures featuring HIS via slow-wave behavior. Due to high-impedance properties of the embedded via wall structures in common ground plane between each antenna element, the mutual coupling path through surface-current can be reduced. Second, in order to minimize leakage power caused by surface-waves, low loss coplanar waveguide ground (CPWG) feeding networks with via wall structures and island-shape pads are realized. The fabricated 4-elements and 8-elements phased array antennas including antenna element and feeding network based on FR-4 PCB achieve wide 3 dB beam coverage while featuring low beam squint in the Ka-band. In order to investigate over-the-air (OTA) system performance at three beam steering scenarios (boresight and ±60° scan angle), the measured maximum error vector magnitude (EVM) in QPSK modulation scheme is 16.6%. The coverage efficiency beyond 50% for the realized gain of −1.5 dBi from 26 to 36 GHz is demonstrated.