Journal
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
Volume 65, Issue 6, Pages 2030-2042Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TMTT.2017.2659227
Keywords
Beam steering; dielectrics; ferroelectric materials; 5G mobile communication; flexible electronics; ink; phase shifters; printed circuits; tuning; varactors
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Funding
- Raytheon Corporation
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This paper presents all-printed varactors and phase shifters using direct-ink writing methodologies on flexible organic films. The key enabler is a novel ferroelectric nanoink that allows printing high dielectric constant, low loss, and electrostatically tunable dielectrics at extremely low temperatures. The dielectric is made by suspending nanoparticles of barium strontium titanate (BST) in thermoplastic cyclic olefin copolymer (COC) to create a multiphase BST/COC nanocomposite. Unlike conventional ferroelectric ceramics, this ferroelectric dielectric requires no sintering and can be printed on any substrate. After printing, it is cured at temperatures below 200 degrees C. Careful stoichiometry and particle analysis of BST powders resulted in identifying conditions for achieving electrostatic tunability. A high relative permittivity of epsilon(r) = 38 and a very low dielectric loss of tan delta = 0.002 at f = 10 GHz were measured for the printed sinterless dielectric. The ink allows printing voltage-variable capacitors with a capacitance tunability up to 10% at microwave frequencies. The tunable capacitors were utilized in a left-handed transmission line design to create all-printed tunable phase shifters with up to a maximum phase shift of Delta phi = 97 degrees and a maximum figure of merit of 29 degrees/dB at f = 10 GHz.
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