Pushing Inkjet Printing to W-Band: An all-printed 90-GHz beamforming array

In this work, the inkjet printing process is refined to push the capabilities of additive manufacturing up to the W-band (75-110 GHz). The idiosyncrasies of inkjet printing on polymer dielectric materials are fully taken into account, to mitigate the effect of excessive ink spreading which results in RF circuit detuning and performance deterioration. The developed process enables the fabrication of the very first inkjet-printed 90 GHz array on a flexible substrate, featuring 5 elements and a 11.3 dBi gain. High fabrication accuracy has been achieved without using any specialized surface treatment equipment, effectively reducing the baseline equipment for mmWave system fabrication to a single inkjet printer and a convection oven. The proof-of-concept array's form factor will allow integration with beam-forming networks; as an example, a miniaturized 4 × 4 Butler matrix is designed with the achieved fabrication space constraints which opens the way for the first fully-printed beamforming arrays operating in W-band with significant fabrication cost savings.