Tunable Phase Shifter Based on Inkjet-Printed Ferroelectric MIM Varactors

This paper presents a new method for the fabrication of tunable multilayer ferroelectric components based on inkjet printing. Inkjet printing is a low-cost technology for selective film fabrication and has high potential for the preparation of tunable dielectric layers for radio frequency and microwave applications. With this technology, tunable metal-insulator-metal (MIM) capacitor is fabricated, that is composed of inkjet-printed Barium-Strontium-Titanate striplines and photo-lithographically structured gold electrodes. Compared to coplanar capacitors, such MIM varactors require significantly lower DC-voltage for tuning. By applying 20 V across a 1 mu m-thick BST film, a tunability of 33% is achieved at 8 GHz and tunability of 60% by applying 50 V. To demonstrate the field of application of this MIM varactor, a tunable phase shifter is designed and fabricated at 8 GHz. A phase shift of 143 degrees and a figure of merit (FoM) of 28 degrees/dB are achieved by applying maximum 50 V tuning voltage.