Tunable microwave devices using low-sintering-temperature screen-printed barium strontium titanate (BST) thick films

Fully Screen‐Printed Tunable Microwave Components Based on Optimized Barium Strontium Titanate Thick Films

“…. The capacitance of the BST varactors remains almost independent of the frequency, what offers a wider range of potential operating frequencies compared with other BST varactors described before . As expected, the capacitance of the device is decreasing with raising tuning field strength due to the change of relative permittivity of BST thick film provoked by the electric field.…”

“…This shifts the optimal operating frequency of a potential microwave device to lower frequencies if a high quality factor is required. In comparison with Palukuru et al ,. the values of quality factors are comparable and even slightly higher.…”

“…Several approaches have been studied to decrease the sintering temperature of BST thick films by adding Li 2 O or B 2 O 3 containing oxides or glass powders . However, compatibility and feasibility studies regarding the development of tunable co‐fired MIM devices based on BST thick films are rarely described in literature so far . In a recent study, BST–ZnO–B 2 O 3 composite thick films have been investigated regarding their suitability as low‐temperature‐sintered tunable microwave dielectrics.…”

Inkjet‐Printed Metal‐Insulator‐Metal Capacitors for Tunable Microwave Applications

“…Compared to already published screen-printed devices, the phase shifter shows a comparable figure of merit (FoM = 6.3-21°/dB, f = 2.5-3.0 GHz [15][16][17][18] ). The achieved phase shift, however, is considerably larger than in the reported publications (Du = 4.5-63°1 [5][6][7][8][9][10][11][12][13][14][15][16][17][18] ). This is believed to be due to the lower film thickness of the inkjet-printed layers, which allows a larger tuning of the varactors at similar biasing voltages.…”

“…[13][14][15][16][17][18] However, all of them use a screen printing process for the device preparation. Yeo et al 13,14 and Hu et al 15,16 present phase shifters with high-temperature sintered dielectric films (>1250°C) and subsequently printed silver electrodes.…”