High-Performance RF Devices and Components on Flexible Cellulose Substrate by Vertically Integrated Additive Manufacturing Technologies

This paper aims to demonstrate that novel additive manufacturing (AM) technologies like metal adhesive laminate and multilayer inkjet printing can be effectively exploited to fabricate high-performing radio-frequency passive components on flexible substrates. Both processes are substrate independent and therefore suitable for manufacturing circuits on several unconventional materials, such as photo-paper. In addition, their complementary features can be combined to develop a novel hybrid process. Proof-of-concept AM prototypes of passive components, such as capacitors and inductors, exhibiting quality factors over 70, never achieved before on paper, and selfresonant frequencies beyond 4 GHz are described. The maximum inductance and capacitance per unit area are 1.4 nH/mm(2) and 6.5 pF/mm(2), respectively. Moreover, an AM RF mixer with a conversion loss below 10 dB is demonstrated still on paper substrate. The mixer, fabricated with the copper adhesive laminate method, operates at 1 GHz and exploits a lumped balun transformer connected to two packaged diodes in series.