mm-Wave UWB Tightly Coupled Dipole Array Realized Using a Hybrid PCB - 3D Printing Fabrication Approach

The key challenge that hinders the realization of mmWave scanning apertures is associated with the fabrication, assembly, and measurement processes. Specifically, there are minimum fabricable feature size constraints for 3D structures. While planar monolithic arrays have been reported, their bandwidth is mainly limited by the height of the array. With this in mind, in this paper, we present a single 2–50 GHz array based on the concept of the tightly coupled dipole arrays (TCDAs). The presented mmWave TCDA uses capacitive overlaps to cancel the ground plane inductance and extend the bandwidth. The array operates across the 5G/6G allocated bands as well as the sub-6 GHz bands that offer lower propagation losses. The paper proposes to overcome the limitations of the PCB fabrication process by using a new hybrid assembly approach, that combines PCB fabrication with 3D printing. Notably, the novel approach follows a two-step process where the dipoles and the overlaps are printed on low-loss substrates with striplines. Then, the antenna boards are assembled vertically using a 3D printed board. The proposed fabrication method is compatible with commercially available 3D printing technology, leading to a simple and low-cost solution. Additionally, a compact double-Y balun is employed to achieve extremely low-cross polarization levels. Indeed, full-wave simulations reveal a continuous operation from 2–50 GHz with VSWR<3 and cross polarization isolation> 40 dB. Concurrently, the array has a very-low profile, where the dipole to ground plane distance is only 1/16 of the wavelength at the lowest frequency of operation. Finally, a prototype is fabricated and measured for operation at the frequencies of 2–40 GHz to validate the proposed fabrication approach.